Amino-terminal End Research Articles

A conserved motif in the immune-subdominant RAP-1 related antigen of Babesia bovis contains a B-cell epitope recognized by antibodies from protected cattle.

Babesia bovis, a tick-borne apicomplexan parasite causing bovine babesiosis, remains a significant threat worldwide, and improved and practical vaccines are needed. Previous studies defined the members of the rhoptry associated protein-1 (RAP-1), and the neutralization-sensitive rhoptry associated protein-1 related antigen (RRA) superfamily in B. bovis, as strong candidates for the development of subunit vaccines. Both RAP-1 and RRA share conservation of a group of 4 cysteines and amino acids motifs at the amino terminal end (NT) of these proteins. Sequence comparisons among the RRA sequences of several B. bovis strains and other Babesia spp parasites indicate a high level of conservation of a 15-amino acid (15-mer) motif located at the NT of the protein. BlastP searches indicate that the 15-mer motif is also present in adenylate cyclase, dynein, and other ATP binding proteins. AlphaFold2 structure predictions suggest partial exposure of the 15-mer on the surface of RRA of three distinct Babesia species. Antibodies in protected cattle recognize a synthetic peptide representing the 15-mer motif sequence in iELISA, and rabbit antibodies against the 15-mer react with the surface of free merozoites in immunofluorescence. The presence of the 15-mer-like regions in dynein and ATP-binding proteins provides a rationale for investigating possible functional roles for RRA. The demonstrated presence of a surface exposed B-cell epitope in the 15-mer motif of the B. bovis RRA, which is recognized by sera from protected bovines, supports its inclusion in future subunit epitope-based vaccines against B. bovis.

439 Patients with mild to moderate atopic dermatitis: a first-in-human, open-label, dose-escalating, nonrandomized clinical trial with AMTX-100

Abstract Atopic dermatitis (AD) is a chronic skin disease that affects approximately 10% of the global population and is characterized by epidermal disruption, microbial invasion, intense pruritus and cytokine mediated inflammation. The pathogenesis of AD is primarily associated with Type 2 immune responses, including the elevated expression of Th2 cytokines such as IL-4, IL-5, IL-13 and IL-31; however, studies have demonstrated roles for epithelial cell-derived cytokines (IL-25, IL-33 and thymic stromal lymphopoietin) and Type 3 immune responses (IL-17, IL-22 and IL-23). Given that AD is a heterogeneous disease with potential for the activation of multiple cytokines at once, there is a growing interest in multi-factorial approaches to therapeutic intervention. Evidence indicates that transcription of many genes overexpressed in AD is controlled predominantly by stress responsive transcription factors (SRTFs) like nuclear factor-kB (NF-kB), the master regulator of inflammation. Nuclear factor-kB is translocated from cytoplasm to the nucleus by a complex of two nuclear transport shuttles, importin α5 (IMPα5) and importin β1 (IMPβ1) after docking of the nuclear localization sequences (NLS) of NF-kB with its binding domain on IMPα5. Once in the nucleus, NF-kB activates genes containing its DNA consensus sequence producing mRNA, which are translated into proteins. AMTX-100 is a novel, chimeric, 100% human, 28-amino acid peptide that contains cell-penetrating sequences at its amino terminal end derived from the fibroblast growth factor 4 signal sequence and a small stretch of the NF-kB amino acid sequences containing an NLS involved in nuclear transport of large transcription factors (SRTFs) that contain a similar NLS. This study aims to identify the maximum tolerated dose, safety, tolerability and efficacy of topically applied AMTX-100 CF 1.1% in adult patients with mild to moderate AD. AMTX-100 CF 1.1% was administered topically twice daily for 7 days at five dose levels. Each patient’s first dose was administered at the study clinic by trained site staff. Remaining doses were self-administered by patients at home. The applied amount of AMTX-100 CF 1.1% depended on the percentage of the body surface area (BSA) affected with AD. The primary and safety endpoints were evaluating maximum dose toxicity and treatment-emergent adverse events. Exploratory endpoints were percent change from baseline of the treated BSA and validated Investigator Global Assessments (vIGA) at Days 7 and 21. This open-label, dose-escalation clinical trial was conducted between March 3, 2020 and October 7, 2021, at four clinical centers in the USA. The study included an up to 21-day screening, 7-day treatment and 14-day follow-up period. Thirty-five patients were assessed for eligibility: nine were excluded and 26 were enrolled. Eligible patients were at least 18 years old with mild to moderate AD diagnosed for at least 6 months prior to enrollment. Patients were referred from sites’ databases and outpatient centers. No dose limiting toxicities, treatment-related AEs, serious AEs or significant changes in laboratory measurements occurred in any cohorts. The mean BSA affected by AD decreased from baseline at the end of treatment visit and follow-up visit by 37.5% (P = 0.001) and 37.9% (P = 0.027), respectively. Across study cohorts, vIGA-AD scores improved after intervention. The findings for this Phase I portion of an Adaptive Phase I/II protocol provides support for safety, tolerability and efficacy of AMTX-100 CF 1.1% in adult patients with mild to moderate AD. AMTX-100 CF 1.1% has advanced into Phase II study including safety, efficacy, gene expression (skin and blood) and proteomics (blood) measurements throughout the study.

NatB Catalytic Subunit Depletion Disrupts DNA Replication Initiation Leading to Senescence in MEFs.

Alpha-aminoterminal acetyltransferase B (NatB) is a critical enzyme responsible for acetylating the aminoterminal end of proteins, thereby modifying approximately 21% of the proteome. This post-translational modification impacts protein folding, structure, stability, and interactions between proteins which, in turn, play a crucial role in modulating several biological functions. NatB has been widely studied for its role in cytoskeleton function and cell cycle regulation in different organisms, from yeast to human tumor cells. In this study, we aimed to understand the biological importance of this modification by inactivating the catalytic subunit of the NatB enzymatic complex, Naa20, in non-transformed mammal cells. Our findings demonstrate that depletion of NAA20 results in decreased cell cycle progression and DNA replication initiation, ultimately leading to the senescence program. Furthermore, we have identified NatB substrates that play a role in cell cycle progression, and their stability is compromised when NatB is inactivated. These results underscore the significance of N-terminal acetylation by NatB in regulating cell cycle progression and DNA replication.

Industrial Processing of Commercially Significant Enzymes

Abstract: Enzymes are highly specific and highly sensitive biocatalyst proteins that play important roles in various life processes. As they are proteins, thus, they are composed of amino acids joined together to form chains. These amino acids are linked by peptide bonds that form between the amino-terminal and carboxylic end. There is the multifaceted application of enzymes in various sectors that include food, textile, paints, pharmaceuticals, leather, oil industries, etc. There is a wide range of sources available for the extraction of enzymes. The commercially important enzymes are generally harvested from microbial sources. Some enzymes are produced extracellularly while some enzymes are produced intracellularly. The production of this bioactive compound could be enhanced by applying suitable optimization techniques, genetic engineering tools, and other modern techniques. One of the major challenges in the commercial production of enzymes is their extraction in pure form without losing their properties. Extraction of enzymes starts from upstream processing that mainly includes two types of fermentation; one is submerged fermentation and another one is solid-state fermentation. After upstream processing, downstream processing is followed which includes cell disruption, filtration, sedimentation and centrifugation, flocculation and coagulation, and chromatography. Then, enzyme purification strategies are followed (salting-out method, dialysis, gel filtration, ion-exchange chromatography, gel electrophoresis. The purpose of down streaming is to purify and concentrate the enzyme from the complex bulk matrix. A significant amount of total production cost is contributed by downstream processing. The review discusses the industrial importance of enzymes and their downstream processing techniques economically and sustainably.

Super-resolution 3D maps to study the antisecretory factor's effects on different GABAa receptor subunits in rat cerebellar granule cells in vitro.

The Antisecretory Factor (AF) is an endogenous protein that inhibits intestinal hypersecretion and various inflammation disorders in vivo. AF has been detected in many mammalian tissues and plasma, but its mechanisms of action are essentially unknown. Previously, we studied the pharmacological action of the AF on GABAA receptors in cerebellar granule cells, comparing the electrophysiological response evoked by two-photon mediated release of caged GABA compounds before and after the administration of AF-16, a 16 amino acids long peptide obtained from the amino-terminal end of the AF protein. After the treatment with AF-16, we observed an increase in the GABAA receptor responses, particularly in those containing the α6 subunit. To figure out the interactions of AF with GABAA receptors in the same cellular model (cerebellar granule cells), we combined immunofluorescence subunits’ staining with confocal and super-resolution microscopy. In particular, we took advantage of an innovative imaging technique that combines stimulated emission depletion (STED) with fluorescence lifetime microscopy (FLIM) to collect super-resolution 3D maps of different subunits distributed on the neuron cell membrane. We explored different approaches to analyze super-resolution fluorescence images obtained by labeling α1 and α6 subunits before and after 1-hour incubation with AF-16. Comparing pre- and post-treatment maps, we found differences in how different subunit populations respond to AF treatment. We critically analyzed these new experimental findings with our previous electrophysiological data to widen the knowledge of the mechanisms of interaction between GABAA receptor subunits and AF protein.

The carboxyl-terminal TSP1-homology domain is the biologically active effector peptide of matricellular protein CCN5 that counteracts profibrotic CCN2

Cellular Communication Network (CCN) proteins have multi-modular structures important for their roles in cellular responses associated with organ development and tissue homeostasis. CCN2 has previously been reported to be secreted as a preproprotein that requires proteolytic activation to release its bioactive carboxyl-terminal fragment. Here, our goal was to resolve whether CCN5, a divergent member of the CCN family with converse functions relative to CCN2, releases the TSP1 homology domain as its bioactive signaling entity. The recombinant CCN5 or CCN3 TSP1 homology domains were produced in ExpiCHO-S or DG44 CHO cells as secretory fusion proteins appended to the carboxyl-terminal end of His-Halo-Sumo or amino-terminal end of human albumin, and purified from the cell culture medium. We tested these fusion proteins in various phosphokinase signaling pathways or cell physiologic assays. Fusion proteins with the CCN5 TSP1 domain inhibited key signaling pathways previously reported to be stimulated by CCN2, irrespective of fusion partner. The fusion proteins also efficiently inhibited CCN1/2-stimulated cell migration and gap closure following scratch wound of fibroblasts. Fusion protein with the CCN3 TSP1 domain inhibited these functions with similar efficacy and potency as that of the CCN5 TSP1 domain. The CCN5 TSP1 domain also recapitulated a positive regulatory function previously assigned to full-length CCN5, i.e. induction of estrogen receptor-α mRNA expression in triple negative MDA-MB-231 mammary adenocarcinoma cells and inhibited epithelial-to-mesenchymal transition and CCN2-induced mammosphere formation of MCF7 adenocarcinoma cells. In conclusion, the CCN5 TSP1 domain is the bioactive entity that confers the biologic functions of unprocessed CCN5.

A mechanistic analysis of bacterial recognition and serine protease cascade initiation in larval hemolymph of Manduca sexta

Serine protease cascades have evolved in vertebrates and invertebrates to mediate rapid defense responses. Previous biochemical studies showed that in hemolymph of a caterpillar, Manduca sexta, recognition of fungi by β-1,3-glucan recognition proteins (βGRP1 and βGRP2) or recognition of bacteria by peptidoglycan recognition protein-1 (PGRP1) and microbe binding protein (MBP) results in autoactivation of hemolymph protease-14 precursor (proHP14). HP14 then activates downstream members of a protease cascade leading to the melanization immune response. ProHP14 has a complex domain architecture, with five low-density lipoprotein receptor class A repeats at its amino terminus, followed by a Sushi domain, a Sushi domain variant called Wonton, and a carboxyl-terminal serine protease catalytic domain. Its zymogen form is activated by specific proteolytic cleavage at the amino-terminal end of the protease domain. While a molecular mechanism for recognition and triggering the response to β-1,3-glucan has been delineated, it is unclear how bacterial recognition stimulates proHP14 activation. To fill this knowledge gap, we expressed the two domains of M. sexta MBP and found that the amino-terminal domain binds to diaminopimelic acid-peptidoglycan (DAP-PG). ProHP14 bound to both the carboxyl-terminal domain (MBP-C) and amino-terminal domain (MBP-N) of MBP. In the mixture of DAP-PG, MBP, and larval plasma, inclusion of an HP14 fragment composed of LDLa repeats 2–5 (LDLa2–5) or MBP-C significantly reduced prophenoloxidase activation, likely by competing with the interactions of the full-length proteins, and suggesting that molecular interactions involving these regions of proHP14 and MBP take part in proHP14 activation in response to peptidoglycan. Using a series of N-terminally truncated versions of proHP14, we found that autoactivation required LDLa2–5. The optimal ratio of PGRP1, MBP, and proHP14 is close to 3:2:1. In summary, proHP14 autoactivation by DAP-type peptidoglycan requires binding of DAP-PG by PGRP1 and the MBP N-terminal domain and association of the LDLa2–5 region of proHP14 with the MBP C-terminal domain. These interactions may concentrate the proHP14 zymogen at the bacterial cell wall surface and promote autoactivation.

The Capsid Precursor Protein of Astrovirus VA1 Is Proteolytically Processed Intracellularly.

Human astrovirus VA1 has been associated with neurological disease in immunocompromised patients, and its recent propagation in cell culture has opened the possibility to study its biology. Unlike classical human astroviruses, VA1 growth was found to be independent of trypsin during virus replication in vitro. In this work, we show that despite its independence on trypsin activation for cell infection, the VA1 capsid precursor protein, of 86 kDa (VP86), is processed intracellularly, and this proteolytic processing is important for astrovirus VA1 infectivity. Antibodies raised against different regions of the capsid precursor showed that the polyprotein can be processed starting at either its amino- or carboxy-terminal end, and they allowed us to identify those proteins of about 33 (VP33) and 38 (VP38) kDa constitute the core and the spike proteins of the mature infectious virus particles, respectively. The amino-terminal end of the spike protein was found to be Thr-348. Whether the protease involved in intracellular cleavage of the capsid precursor is of viral or cellular origin remains to be determined, but the cleavage is independent of caspases. Also, trypsin is able to degrade the capsid precursor but has no effect on VP33 and VP38 proteins when assembled into virus particles. These studies provide the basis for advancement of the knowledge of astrovirus VA1 cell entry and replication. IMPORTANCE Human astrovirus VA1 has been associated with neurological disease in immunocompromised patients. Its recent propagation in cell culture has facilitated the study of its biology. In this work, we show that despite the ability of this virus to grow in the absence of trypsin, a marked feature of human classical astroviruses, the capsid precursor protein of astrovirus VA1 is cleaved intracellularly to yield the mature infectious particles, formed by two polypeptides, VP33 that constitutes the core domain of the virus particle, and VP38 that forms the spike of the virus. These studies provide a platform to advance our knowledge on astrovirus VA1 cell entry and replication.

Genomic evolution of the Coronaviridae family

The current outbreak of coronavirus disease-2019 (COVID-19) caused by SARS-CoV-2 poses unparalleled challenges to global public health. SARS-CoV-2 is a Betacoronavirus, one of four genera belonging to the Coronaviridae subfamily Orthocoronavirinae. Coronaviridae, in turn, are members of the order Nidovirales, a group of enveloped, positive-stranded RNA viruses. Here we present a systematic phylogenetic and evolutionary study based on protein domain architecture, encompassing the entire proteomes of all Orthocoronavirinae, as well as other Nidovirales. This analysis has revealed that the genomic evolution of Nidovirales is associated with extensive gains and losses of protein domains. In Orthocoronavirinae, the sections of the genomes that show the largest divergence in protein domains are found in the proteins encoded in the amino-terminal end of the polyprotein (PP1ab), the spike protein (S), and many of the accessory proteins. The diversity among the accessory proteins is particularly striking, as each subgenus possesses a set of accessory proteins that is almost entirely specific to that subgenus. The only notable exception to this is ORF3b, which is present and orthologous over all Alphacoronaviruses. In contrast, the membrane protein (M), envelope small membrane protein (E), nucleoprotein (N), as well as proteins encoded in the central and carboxy-terminal end of PP1ab (such as the 3C-like protease, RNA-dependent RNA polymerase, and Helicase) show stable domain architectures across all Orthocoronavirinae. This comprehensive analysis of the Coronaviridae domain architecture has important implication for efforts to develop broadly cross-protective coronavirus vaccines.

The porcine cerebellin gene family.

Cerebellins (CBLN1-4), together with C1qTNF proteins, belong to the CBLN subfamily of C1q proteins. Cerebellin-1 (CBLN1) is active in synapse formation and functions at the parallel fiber-Purkinje cell synapses. Cerebellins form tripartite complexes with neurexins and the glutamate-receptor-related proteins GluD1 and GluD2, playing a role as trans-synaptic cell-adhesion molecules that critically contribute to both synapse formation and functioning and brain development. In this study, I present a molecular characterization of the four porcine CBLN genes. Experimental data and in silico analyses collectively describes the gene structure, chromosomal localization, and expression of CBLN1-4. Two cDNAs encoding the cerebellins CBLN1 and CBLN3 were RT-PCR cloned and sequenced. The nucleotide sequence of the CBLN1 clone contains an open reading frame of 582 nucleotides and encodes a protein of 193 amino acids. The deduced amino acid of the porcine CBLN1 protein was 99% identical to both mouse CBLN1 and to human CBLN1. The deduced CBLN1 protein contains a putative signal sequence of 21 residues, two conserved cysteine residues, and C1q domain. The nucleotide sequence of the CBLN3 cDNA clone comprises an open reading frame of 618 nucleotides and encodes a protein of 205 amino acids. The deduced amino acid sequence of the porcine CBLN3 protein was 88% identical to mouse CBLN3 and 94% identical to human CBLN3. The amino terminal ends of both the CBLN1 and CBLN3 proteins contain three possible N-linked glycosylation sites. The genomic organization of both porcine CBLN1 and CBLN3 is very similar to those of their human counterparts. The expression analyses demonstrated that CBLN1 and CBLN3 transcripts are predominantly expressed in the cerebellum. The sequences of the porcine precerebellin genes and cDNAs were submitted to DDBJ/EMBL/GenBank under the following accession numbers: CBLN1 gene (GenBank ID: FJ621565), CBLN1 cDNA (GenBank ID: EF577504), CBLN3 gene (GenBank ID: FJ621566), CBLN3 cDNA (GenBank ID: EF577505) and CBLN4 cDNA (GenBank ID: FJ196070).

Dysfibrinogenemia-Potential Impact of Genotype on Thrombosis or Bleeding.

The congenital dysfibrinogenemias, most often associated with bleeding disorders, encompass mutations in the amino-terminal end of fibrinogen α-chain consisting of Gly17-Pro18-Arg19-Val20, known as knob A, which is a critical site for fibrin polymerization. Here we review the studies reporting dysfibrinogenemia due to mutations affecting fibrinogen knob A and identified 29 papers. The number of reports on dysfibrinogenemias related to residues Gly17, Pro18, Arg19, and Val20 is 5, 4, 18, and 2, respectively. Dysfibrinogenemias related to residues Gly17, Pro18, and Val20 are exclusively associated with bleeding tendency. However, the clinical picture associated with dysfibrinogenemia related to residue Arg19 varies, with most patients suffering from bleeding tendencies, but also transitory ischemic attacks and retinal thrombosis may occur. The reason for this variation is unclear. To elaborate the genotype-phenotype associations further, we studied a Danish family with knob A-related dysfibrinogenemia caused by the Aα Arg19Gly (p.Arg19Gly) mutation using whole-exome sequencing and fibrin structure analysis. Our family is the first reported carrying the p.Arg19Gly mutation combined with one or more single nucleotide polymorphisms (SNP)s in FGA, FGB, and/or FGG and increased fibrin fiber thickness and fibrin mass-to-length ratio suffering from pulmonary emboli, suggesting that compound genotypes may contribute to the thrombogenic phenotype of these patients. Our review, accordingly, focuses on significance of SNPs, compound genotypes, and fibrin structure measures affecting the genotype-phenotype associations in fibrinogen knob A mutations.

Small Angle X-Ray Scattering Reveals the Conformation of β2glycoprotein I and the Conformational Binding Epitopes of Autoantibodies

Despite the fact that autoantibodies to a variety of antigens have been described in patients with the antiphospholipid syndrome (APS), it is now generally accepted that β2glycoprotein I (β2GPI) is a primary target of pathogenic autoantibodies in APS patients. Unraveling the immunodominant epitope of β2GPI at the molecular/conformational level may help to understand the disease and develop specific therapies. β2GPI is an abundant plasma protein that, upon interaction with negative phospholipids, has been shown to undergo a conformational change resulting in the exposure of a pathogenic epitope on domain I. Although the conformation of β2GPI has been previously reported by small angle X-ray scattering (SAXS), we are the first to show the interaction with autoimmune anti-β2GPI antibodies. We previously showed that antibodies towards the cryptic domain I epitope are highly associated with both thrombosis and pregnancy morbidity. Previous studies indicated that amino acids R39-R43 and the interlinking region between domains I and II are part of this cryptic epitope. However, these studies used point-mutated variants of β2GPI, and the results could be influenced by structural changes compared to native β2GPI.In this study, we visualized the conformation of β2GPI in solution by SAXS and its interaction with two anti-domain I antibodies, obtained via B cell isolation from two APS patients. Antibody P2-6 previously showed affinity for domain I regardless of the conformation of β2GPI, whereas antibody P1-117 only recognized domain I of β2GPI upon binding to anionic phospholipids. Via point-mutated variants of β2GPI we previously demonstrated that P1-117 is reactive against the cryptic domain I epitope including epitope G40-R43. In a first set of SAXS experiments, we visualized plasma purified β2GPI in its native conformation. We found that, due to the flexibility of domain I-III of β2GPI, β2GPI is able to adapt into several different conformations ranging from a sort of circular shape into a S shape, confirming results of previous studies. Upon increasing the pH, the conformation of β2GPI changed into a more erect fish-hook conformation resembling the crystal structure of β2GPI. The three-dimensional structures of both antibodies were determined by SAXS and allowed to react with β2GPI in the open conformation (Figure 1). Antibody P2-6 interacted mainly with the amino terminal end of domain I of β2GPI which is available in both the native and open conformations of β2GPI. In contrast, antibody P1-117 interacted with a broader part of the protein, identifying a discontinuous and conformational epitope covering domain I, the interlinking region and a small part of domain II. Importantly, (part of) the epitope is not available in the native closed conformation of β2GPI due to its interaction with domain V (circular conformation) or due to a carbohydrate chain positioned on the interface of domain I-II (S shaped conformation). These data confirm the importance of the conformation of β2GPI coated on the solid phase of diagnostic anti-β2GPI assays to avoid false negative classification of APS patients.In conclusion, our findings contribute to elucidating the conformation of β2GPI in solution and clearly indicate that pathogenic autoantibodies bind a discontinuous conformational epitope. Identification of this conformational epitope will allow optimization of peptide-based therapies and also epitope-specific diagnostic assays that will enable the stratification of patients according to their risk on thrombosis/pregnancy morbidity. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Amino- and carboxyl-terminal ends of the bovine parainfluenza virus type 3 matrix protein are important for virion and virus-like particle release

Paramyxovirus matrix (M) proteins are key drivers of virus particle assembly and budding at the plasma membrane. To identify regions important for the M protein function, we generated a series of deletion mutants of the bovine parainfluenza virus type 3 (BPIV3) M protein. We found that M proteins lacking 10 amino acids in the amino-terminal end (ΔN10) or 4 amino acids in the carboxyl-terminal end (ΔC4) did not support M-deficient BPIV3 virion release and M protein-induced virus-like particle (VLP) release. Both ΔN10 and ΔC4 retained M protein-M protein and M protein-nucleocapsid (N) protein interactions. However, neither was transported to the plasma membrane. Our results indicate that both amino- and carboxyl-terminal ends of the BPIV3 M protein are essential for M protein transport to the plasma membrane, where it facilitates virion and VLP release.

Synthesis, Characterisation and Mesophase Transition of Hexasubstituted Cyclotriphosphazene Molecules with Schiff Base and Azo Linking Units and Determination of Their Fire Retardant Properties

Hexakis(oxy-4-benzaldehyde)cyclotriphosphazene, 1 was successfully synthesised by nucleophilic substitution reaction between hexachlorocyclotriphosphazene, HCCP and 4-hydroxybenzaldehyde. Azotization reaction of p-nitroaniline with phenol formed 4-(4-nitrophenylazo)phenol, 2 which was alkykated with heptyl, nonyl, decyl, dodecyl and tetradecylbromide to give a series of nitro compounds, 3a-e. Reduction of 3a-e and 2 formed the subsequent amine compounds 4a-f, 4-(4-alkyloxyphenylazo)phenylamine. Another similar reaction of protected aniline with a series of substituted aniline formed a series of compounds 4g-i. A series of hexasubstituted cyclotriphosphazene molecules containing Schiff base and azo linking units, 5a-i were synthesised from the reaction between intermediates 1 and 4a-i. Further reduction of compound 5i afford compound 5j with amino terminal end. All the synthesised intermediates and compounds were characterised using Fourier Transform Infrared spectroscopy (FT-IR), 1H and 13C Nuclear Magnetic Resonance spectroscopy (NMR) and CHN elemental analysis. The liquid crystal properties of intermediates and final compounds were determined using Polarised Optical Microscope (POM) and their phase transitions confirmed using Differential Scanning Calorimetry (DSC). Only intermediates 3a-e showed mesophase of smectic A and compounds 5a-e with alkoxy chain were mesogenic with smectic A and nematic phases. In addition, compound 5h exhibited nematic phase only. However, all the other intermediates and compounds were found to be non-mesogenic. Furthermore, the fire retardant of final compounds were determined using Limiting Oxygen Index (LOI) testing. The LOI value of pure polyester resin was increased from 22.53 to 24.71% when incorporated with 1 wt% of HCCP. Moreover, all the final compounds showed a positive in LOI value the highest LOI value was belonged to compound 5i with 27.90%.

Gas sorption and diffusion in poly(dimethylsiloxane) (PDMS)/graphene oxide (GO) nanocomposite membranes

Gas solubility and diffusivity are reported for a series of poly(dimethylsiloxane) (PDMS)/graphene oxide (GO) nanocomposites. The nanocomposites were prepared via a crosslinking reaction between the amino-terminal end groups of the telechelic PDMS and epoxide groups on the surface of GO. Gas solubilities of N2, O2, CH4, and CO2 were measured at 35 °C over a range of pressures. Gas solubility in the nanocomposites was unaffected by GO at the maximum loading of 8 wt%. Therefore, a previously reported decrease in the nanocomposite permeability with increasing GO content was due to a reduction in diffusivity. The pure-gas selectivity of the nanocomposite was controlled by diffusivity selectivity, and both increased with increasing GO content. Based on Meares’ formula, correlations between diffusivity and the square of the kinetic diameter were observed for the nanocomposites. The slopes of these correlations increased progressively as a function of GO content, indicating the enhanced size-sieving ability of the nanocomposites.

Maturation of NAA20 Aminoterminal End Is Essential to Assemble NatB N-Terminal Acetyltransferase Complex

Protein lifespan is regulated by co-translational modification by several enzymes, including methionine aminopeptidases and N-alpha-aminoterminal acetyltransferases. The NatB enzymatic complex is an N-terminal acetyltransferase constituted by two subunits, NAA20 and NAA25, whose interaction is necessary to avoid NAA20 catalytic subunit degradation. We found that deletion of the first five amino acids of hNAA20 or fusion of a peptide to its amino terminal end abolishes its interaction with hNAA25. Substitution of the second residue of hNAA20 with amino acids with small, uncharged side-chains allows NatB enzymatic complex formation. However, replacement by residues with large or charged side-chains interferes with its hNAA25 interaction, limiting functional NatB complex formation. Comparison of NAA20 eukaryotic sequences showed that the residue following the initial methionine, an amino acid with a small uncharged side-chain, has been evolutionarily conserved. We have confirmed the relevance of second amino acid characteristics of NAA20 in NatB enzymatic complex formation in Drosophila melanogaster. Moreover, we have evidenced the significance of NAA20 second residue in Saccharomyces cerevisiae using different NAA20 versions to reconstitute NatB formation in a yNAA20-KO yeast strain. The requirement in humans and in fruit flies of an amino acid with a small uncharged side-chain following the initial methionine of NAA20 suggests that methionine aminopeptidase action may be necessary for the NAA20 and NAA25 interaction. We showed that inhibition of MetAP2 expression blocked hNatB enzymatic complex formation by retaining the initial methionine of NAA20. Therefore, NatB-mediated protein N-terminal acetylation is dependent on methionine aminopeptidase, providing a regulatory mechanism for protein N-terminal maturation.

An internal amino-terminal FLAG-tag octapeptide alters oligomerization of expressed surfactant protein-A

Pulmonary surfactant protein-A (SP-A) is expressed by lung alveolar and bronchiolar epithelial cells and plays a critical role in innate immunity of the lung. Exposure of the lung to various environmental insults alters SP-A homeostasis. To investigate the cellular mechanisms involved in these alterations, we added the FLAG octapeptide (DYKDDDDK) to the carboxy-terminus (SP-A/C-FLAG) or near the amino-terminus (SP-A/N-FLAG) of mouse SP-A (WT-SP-A) to tag specific pools of protein. We hypothesized that addition of FLAG would have negligible effects on SP-A expression, oligomerization and secretion. Analysis of Chinese hamster ovary cells expressing these proteins indicated that tagged SP-A mRNA could be distinguished from WT-SP-A by northern analysis and RT-PCR using sequence-specific oligonucleotides. Tagged SP-A protein could be differentiated from WT-SP-A by western analysis using antibodies specific for the FLAG epitope. Subcellular fractionation and immunocytochemistry indicated the majority of each protein was present in punctuate (presumably endocytic) vesicles, and all forms of SP-A protein were secreted. These results suggest that a FLAG epitope added to the carboxy-terminus or inserted into the amino-terminus of the mature SP-A protein has little effect on its expression and cellular processing. However, disruptions of the amino-terminal end of SP-A prevents proper oligomerization, suggesting that this region of mature SP-A is critical in proper oligomeric assembly and is not useful for studies intended to define mechanisms underlying SP-A homeostasis.

Pine wood nematode (PWN)-secretory antigen 571 as a biomarker for the PWN and its monoclonal antibodies for detecting PWN and its infected pine tree

• PWN-SA571 is a biomarker for PWN. • Specific Mabs for PWN-SA571 were generated. • PWN-SA571 Mabs could detect PWN and PWNIPT by ELISA and dot blots. • PWN-SA571 Mabs could detect antigens by LFA. The biochemical characteristics of pine wood nematode (PWN)-secretory antigen 571 (PWN-SA571) identified from the PWN secretome and PWN-infected pine tree extracts (PWNIPT) were investigated. PWN-SA571 has homologs in various nematodes in diverse families and a signal peptide at the amino-terminal end. Since it was not possible to express the full-length PWN-SA571 protein, two peptides showing high antigenicity were synthesized and used as antigens for generating monoclonal antibodies (Mabs). Mab-secreting fusion hybridoma cell lines were selected based on immunoreactivity to free peptide and BSA-conjugated peptide (BSA pep) antigens by enzyme-linked immunosorbent assay for establishing Mab-secreting hybridoma lines. Ascites containing PWN-SA571-specific Mabs showed stronger immunoreactivity to PWNIPT than to healthy pine tree extracts. In addition, PWN-SA571-specific Mabs could recognize less than 20 ng of BSA pep in lateral flow assays. Furthermore, purified biotin-conjugated PWN-SA571-specific Mab IgG or IgM were able to detect BSA pep (<15 ng) and PWN extracts (<600 ng). Taken together, these results demonstrate that PWN-SA571-specific Mabs could detect PWN or PWNIPT extracts by ELISA, LFA, or dot blot analysis.

Mycoplasma bovis Membrane Protein MilA Is a Multifunctional Lipase with Novel Lipid and Glycosaminoglycan Binding Activity.

The survival, replication, and virulence of mycoplasmas depend on their ability to capture and import host-derived nutrients using poorly characterized membrane proteins. Previous studies on the important bovine pathogen Mycoplasma bovis demonstrated that the amino-terminal end of an immunogenic 226-kDa (P226) protein, encoded by milA (the full-length product of which has a predicted molecular weight of 303 kDa), had lipase activity. The predicted sequence of MilA contains glycosaminoglycan binding motifs, as well as multiple copies of a domain of unknown function (DUF445) that is also found in apolipoproteins. We mutagenized the gene to facilitate expression of a series of regions spanning the gene in Escherichia coli Using monospecific antibodies against these recombinant proteins, we showed that MilA was proteolytically processed into 226-kDa and 50-kDa fragments that were both partitioned into the detergent phase by Triton X-114 phase fractionation. Trypsin treatment of intact cells showed that P226 was surface exposed. In vitro, the recombinant regions of MilA bound to 1-anilinonaphthalene-8-sulfonic acid and to a variety of lipids. The MilA fragments were also shown to bind heparin. Antibody against the carboxyl-terminal fragment inhibited the growth of M. bovisin vitro This carboxyl end also bound and hydrolyzed ATP, suggestive of a potential role as an autotransporter. Our studies have demonstrated that DUF445 has lipid binding activity and that MilA is a multifunctional protein that may play multiple roles in the pathogenesis of infection with M. bovis.

Identification of two abundant Aerococcus urinae cell wall-anchored proteins

Aerococcus urinae is an emerging pathogen that causes urinary tract infections, bacteremia and infective endocarditis. The mechanisms through which A. urinae cause infection are largely unknown. The aims of this study were to describe the surface proteome of A. urinae and to analyse A. urinae genomes in search for genes encoding surface proteins. Two proteins, denoted Aerococcal surface protein (Asp) 1 and 2, were through the use of mass spectrometry based proteomics found to quantitatively dominate the aerococcal surface. The presence of these proteins on the surface was also shown using ELISA with serum from rabbits immunized with the recombinant Asp. These proteins had a signal sequence in the amino-terminal end and a cell wall-sorting region in the carboxy-terminal end, which contained an LPATG-motif, a hydrophobic domain and a positively charged tail. Twenty-three additional A. urinae genomes were sequenced using Illumina HiSeq technology. Six different variants of asp genes were found (denoted asp1-6). All isolates had either one or two of these asp-genes located in a conserved locus, designated Locus encoding Aerococcal Surface Proteins (LASP). The 25 genomes had in median 13 genes encoding LPXTG-proteins (range 6–24). For other Gram-positive bacteria, cell wall-anchored surface proteins with an LPXTG-motif play a key role for virulence. Thus, it will be of great interest to explore the function of the Asp proteins of A. urinae to establish a better understanding of the molecular mechanisms by which A. urinae cause disease.