Protein Fragments Research Articles

Blm10-Based Compounds Add to the Knowledge of How Allosteric Modulators Influence Human 20S Proteasome.

Proteasomes catalyze protein degradation in cells and play an integral role in cellular homeostasis. Its activity decreases with age alongside the load of defective proteins, resulting from mutations or oxidative stress-induced damage. Such proteins are prone to aggregation and, if not efficiently degraded, can form toxic oligomers and amyloid plaques. Developing an effective way to activate the proteasome could prevent such pathologies. Designing activators is not easy because they do not bind in the active site, which is well-defined and highly conserved, but away from it. The structures of proteasome complexes with natural activators can help here, but these are large proteins, some even multimeric, whose activity is difficult to replace with a small-molecule compound. Nevertheless, the use of fragments of such proteins makes it possible to accumulate knowledge about the relevance of various structural elements for efficient and selective activation. Here, we presented peptidic activators of the 20S proteasome, which were designed based on both the C-terminal sequence of the yeast proteasome activator, Blm10 protein, and the interactions predicted by molecular modeling. These Blm analogs were able to stimulate human 20S proteasome to more efficiently degrade both small fluorogenic substrates and proteins. The best activators also demonstrated their efficacy in cell lysates. X-ray crystallography indicated that an effective modulator can bind to several sites on the surface of the proteasome without causing permanent structural changes in its immediate vicinity but affecting the active sites.

High-throughput discovery of inhibitory protein fragments with AlphaFold.

Peptides can bind to specific sites on larger proteins and thereby function as inhibitors and regulatory elements. Peptide fragments of larger proteins are particularly attractive for achieving these functions due to their inherent potential to form native-like binding interactions. Recently developed experimental approaches allow for high-throughput measurement of protein fragment inhibitory activity in living cells. However, it has thus far not been possible to predict de novo which of the many possible protein fragments bind to protein targets, let alone act as inhibitors. We have developed a computational method, FragFold, that employs AlphaFold to predict protein fragment binding to full-length proteins in a high-throughput manner. Applying FragFold to thousands of fragments tiling across diverse proteins revealed peaks of predicted binding along each protein sequence. Comparisons with experimental measurements establish that our approach is a sensitive predictor of fragment function: Evaluating inhibitory fragments from known protein-protein interaction interfaces, we find 87% are predicted by FragFold to bind in a native-like mode. Across full protein sequences, 68% of FragFold-predicted binding peaks match experimentally measured inhibitory peaks. Deep mutational scanning experiments support the predicted binding modes and uncover superior inhibitory peptides in high throughput. Further, FragFold is able to predict previously unknown protein binding modes, explaining prior genetic and biochemical data. The success rate of FragFold demonstrates that this computational approach should be broadly applicable for discovering inhibitory protein fragments across proteomes.

Identifying novel heterozygous PI4KA variants in fetal abnormalities

BackgroundThe clinical manifestations of PI4KA-related disorders are characterized by considerable variability, predominantly featuring neurological impairments, gastrointestinal symptoms, and a combined immunodeficiency. The aim of this study was to delineate the novel spectrum of PI4KA variants detected prenatally and to assess their influence on fetal development.MethodsA thorough fetal ultrasound screening was conducted, supplemented by both antenatal and post-abortion magnetic resonance imaging (MRI) studies. Novel PI4KA variants were detected through clinical Whole exon sequencing (WES) and validated by Sanger sequencing. The functional consequences of these variants were evaluated using bioinformatics tools. The effects of the identified variants on splicing were analyzed through minigene splicing assays. Subsequently, both wild-type and mutant PI4KA protein fragments were purified, and their enzymatic activities were quantitatively assessed.ResultsUltrasound imaging, MRI scans revealed a dilated small intestine with an obstruction. Compound heterozygous variants (NM_058004.3: c.2802_2863-40del and c.2819 C > T, p.Ala940Val) were identified in the PI4KA of the affected fetus through clinical trio-WES. Both variants were predicted deleterious. The PI4KA variant c.2802_2863-40del resulted in the production of three distinct mRNA isoforms. The PI4KA variant c.2819 C > T (p.Ala940Val) significantly reduced the enzyme activity.ConclusionsThis study extended the mutational spectrum of PI4KA and may provide guidance for genetic counseling. Functional studies confirmed that the identified variant induces alterations in RNA splicing and impairs enzyme activity.

Validation of a one-step reverse transcription PCR detection method for Tobamovirus maculatessellati, in tomato (Solanum lycopersicum L.) and pepper (Capsicum annuum L.)

The solanaceous-infecting tobamoviruses are closely related and hence it can be challenging to detect them using serological or molecular methods, particularly when present in a mixed infection. Tomato mottle mosaic virus (ToMMV) is a newly identified tobamovirus that poses serious risk to tomato (Solanum lycopersicum L.) and pepper (Capsicum annuum L.) production worldwide. Species-specific identification is crucial to prevent the entry and establishment of plant pathogens and protect the billion-dollar tomato industry. In this study, we report the validation of a previously described reverse transcription polymerase chain reaction (RT-PCR) assay that amplifies a 289 bp fragment of the coat protein coding region of ToMMV genome. This assay has 100% specificity for ToMMV. Inclusivity tests were performed against a diverse collection of six ToMMV isolates in North America. Exclusivity tests showed no cross reaction with eleven non-target viruses and seven viroids commonly found on tomato and pepper host plants. The detection limit of the one-step RT-PCR was determined to be at 10-5 (or 0.25pg/μl) dilution in plant samples, with its amplicon sequence confirmed by Sanger sequencing. The RT-PCR can detect ToMMV consistently on contaminated seed or leaf tissues. This validated assay could serve as a standard method for detecting ToMMV in seed health testing and for plant disease diagnosis, thus to prevent inadvertent introduction and spread of this emerging and economically important tobamovirus in tomato and pepper fields.

Type IV collagen derived non-collagenous domain α6 (IV) NC1 and its derivative fragments inhibit endothelial cell proliferation and attenuates in-vivo chorioallantoic membrane angiogenesis.

Targeting tumor angiogenesis with safe endogenous protein inhibitors is a promising therapeutic approach despite the plethora of the first line of emerging chemotherapeutic drugs. The extracellular matrix network in the blood vessel basement membrane and growth factors released from endothelial and tumor cells promote the neovascularization which supports the tumor growth. Contrastingly, small cleaved cryptic fragments of the C-terminal non collagenous domains of the same basement membrane display antiangiogenic effect. In the present study, full length α6(IV)NC1(Hexastatin) and its three subfragments α6S1(IV)NC1, α6S2(IV)NC1, and α6S3(IV)NC1 were validated for their pro-apoptotic and angio-inhibitory property. In order to construct the coding sequence of hexastatin and its three derivative partial peptide fragments were constructed with our proposed method, where the corresponding exons were amplified from the genomic DNA and then assembled together. Coding sequences were cloned and expressed using pLATE31 vector and recombinant proteins were purified with C-terminal His tag. The endogenous NC protein fragments of collagen IV were evaluated in vitro for their role in cytotoxicity on human umbilical vein endothelial cells (HUVECs). The results showed that the NC1 domain and its fragments inhibited the HUVECs cell proliferation, migration, invasion and induced apoptosis. The neovascularization inhibition was studied in in-vitro, via tube formation assay and in-vivo via the CAM Assay. The results showed that blood vessels and inter capillary network were inhibited in endothelial cells and also, in chick embryo treated with recombinant α6(IV)NC1 and its derivatives, except for α6S1(IV)NC1 and these endogenous protein inhibitors act as bio-therapeutics in inhibition of angiogenesis.

Role of Copper and Zinc Ions in the Hydrolytic Degradation of Neurodegeneration-Related Peptides.

Spontaneous cleavage reactions normally occur in vivo on amino acid peptide backbones, leading to fragmentation products that can have different physiological roles and toxicity, particularly when the substrate of the hydrolytic processes are neuronal peptides and proteins highly related to neurodegeneration. We report a hydrolytic study performed with the HPLC-MS technique at different temperatures (4 °C and 37 °C) on peptide fragments of different neuronal proteins (amyloid-β, tau, and α-synuclein) in physiological conditions in the presence of Cu2+ and Zn2+ ions, two metal ions found at millimolar concentrations in amyloid plaques. The coordination of these metal ions with these peptides significantly protects their backbones toward hydrolytic degradation, preserving the entire sequences over two weeks in solution, while the free peptides in the same buffer are fully fragmented after the same or even shorter incubation period. Our data show that peptide cleavage is not only ruled by the chemical sensitivity of amino acids, but the peptide conformation changes induced by metal coordination influence hydrolytic reactions. The enhanced stability of neuronal peptides provided by metal coordination can increase local levels of amyloidogenic species capable of seeding fibril growth, resulting in aberrant protein depositions and deficits in neuronal activity.

Expression and purification of E140 protein antigen fragments of Plasmodium vivax and Plasmodium berghei for serological assays.

Malaria, a life-threatening disease caused by Plasmodium parasites, continues to pose a significant global health threat, with nearly 250 million infections and over 600 000 deaths reported annually by the WHO. Fighting malaria is particularly challenging partly due to the complex life cycle of the parasite. However, technological breakthroughs such as the development of the nucleoside-modified mRNA lipid nanoparticle (mRNA-LNP) vaccine platform, along with the discovery of novel conserved Plasmodium antigens such as the E140 protein, present new opportunities in malaria prevention. Importantly, production of recombinant proteins for malaria vaccine evaluation by serological assays often represents an additional hurdle because many Plasmodium proteins are complex and often contain transmembrane domains that make production and purification particularly difficult. This research protocol provides a step-by-step guide for the production and purification of P. berghei and P. vivax E140 protein fragments that can be used to test humoral immune responses against this novel malaria vaccine target. We demonstrate that the purified proteins can be successfully used in enzyme-linked immunosorbent assay (ELISA) to evaluate antigen-specific binding antibody responses in sera obtained from E140 mRNA-LNP-vaccinated mice. Therefore, these proteins can contribute to the development and evaluation of E140-based malaria vaccines.

Conformational Engineering of Flexible Protein Fragments on the Surface of Different Nanoparticles: The Surface-Atom Mobility Rules.

As a newly emerging technology, conformational engineering (CE) has been gradually displaying the power of producing protein-like nanoparticles (NPs) by tuning flexible protein fragments into their original native conformation on NPs. But apparently, not all types of NPs can serve as scaffolds for CE. To expedite the CE technology on a broader variety of NPs, the essential characteristic of NPs as scaffolds for CE needs to be identified. Herein, we investigate the potential of two distinct types of NPs as scaffolds for CE: CdSe/ZnS quantum dots (QDs), an ionic compound NP, and palladium NPs (PdNPs), a metal NP. The results demonstrate that while QDs cannot support the restoration of the native conformation and function of the complementary-determining region (CDR) fragments of antibodies, PdNPs can. The notably disparate outcomes unequivocally show that the mobility of the surface atoms/adatoms of the NPs or the mobility of the conjugating bonds to the NPs is essential for CE, which allows the conjugated peptides to undergo a conformational change from their initial random conformation to their most stable native conformation under the constraints mimicking the native long-range interactions in the original proteins. This discovery opens the door for CE on more NPs in the future.

Cholesterol Attenuates the Pore-Forming Capacity of CARC-Containing Amphipathic Peptides.

Artificial peptides P4, A1 and A4 are homologous to amphipathic α-helical fragments of the influenza virus M1 protein. P4 and A4 contain the cholesterol recognition sequence CARC, which is absent in A1. As shown previously, P4 and A4 but not A1 have cytotoxic effects on some eukaryotic and bacterial cells. This might be caused by the dysfunction of cholesterol-dependent cellular structures, inhibition of the respiratory chain, or disruption of the membrane. Here, we analyzed the latter hypothesis by studying the uncoupling effect of the peptides on asolectin membranes. The influence of A4 on Δψ pre-formed either by the valinomycin-dependent K+ diffusion or by the activity of membrane-built cytochrome c oxidase (CcO) was studied on (proteo)liposomes. Also, we investigated the effect of P4, A1 and A4 on liposomes loaded with calcein. It is found that A4 in a submicromolar range causes an immediate and complete dissipation of diffusion Δψ across the liposomal membrane. Uncoupling of the CcO-containing proteoliposomes requires an order of magnitude of higher peptide concentration, which may indicate the sorption of A4 on the enzyme. The presence of cholesterol in the membrane significantly weakens the uncoupling. Submicromolar A4 and P4 cause the release of calcein from liposomes, indicating the formation of membrane pores. The process develops in minutes and is significantly decelerated by cholesterol. Micromolar A1 induces pore formation in a cholesterol-independent manner. We conclude that the peptides P4, A4 and, in higher concentrations, A1 form pores in the asolectin membrane. The CARC-mediated interaction of A4 and P4 with cholesterol impedes the peptide oligomerization necessary for pore formation. The rapid uncoupling effect of A4 is apparently caused by an increase in the proton conductivity of the membrane without pore formation.

Use of an Intramolecular Quenched Fluorescence (IQF) Cleavage Assay for Assessing Enzyme Kinetics of Gamma-Secretase in Human Skin Fibroblasts and Keratinocytes.

This study describes an intramolecular quenching assay to evaluate gamma-secretase (GS) enzyme activity in human dermal cells. The method utilizes a fluorogenic peptide substrate, mimicking a fragment of amyloid precursor protein (APP), in which a quencher suppresses the fluorescence of a fluorophore until enzymatic cleavage occurs, resulting in a measurable increase in fluorescence. This real-time, direct measurement of GS activity allows for precise kinetic analysis using Michaelis-Menten modeling to define Kd and Vmax. The assay is designed to quantify GS activity in human dermal fibroblasts and keratinocytes, enabling comparison between samples derived from hidradenitis suppurativa (HS) patients and healthy controls, as well as investigating the effects of subunit knockdown, such as nicastrin, on GS function. The method offers several advantages, including simplicity, cost-effectiveness, and adaptability for high-throughput screening for GS enzyme inhibitors.

A protein interaction map of the myosin Myo2 reveals a role of Alo1 in mitochondrial inheritance in yeast.

Budding yeast cells multiply by asymmetric cell division. During this process, the cell organelles are transported by myosin motors along the actin cytoskeleton into the growing bud, while at the same time some organelles must be retained in the mother cell. The ordered partitioning of organelles depends on highly regulated binding of motor proteins to cargo membranes. To search for novel components involved in this process, we performed a protein fragment complementation screen using the cargo binding domain of Myo2, the major organelle transporter in yeast, as a bait and a genome-wide strain collection expressing yeast proteins as prey. One robust hit was Alo1, a poorly characterized D-arabinono-1,4-lactone oxidase located in the mitochondrial outer membrane. We found that mutants lacking Alo1 exhibit defects in mitochondrial morphology and inheritance. During oxidative stress dysfunctional mitochondria are immobilized in the mother in wild type cells. Intriguingly, overexpression of ALO1 restores bud-directed transport of mitochondria under these conditions. We propose that Alo1 supports the recruitment of Myo2 to mitochondria and its activity is particularly important under oxidative stress.

Native Mass Spectrometry Captures the Conformational Plasticity of Proteins with Low-Complexity Domains.

Disordered regions are an important functional feature of many multidomain proteins. A prime example is proteins in membraneless organelles, which contain folded domains that engage in specific interactions and disordered low-complexity (LC) domains that mediate liquid-liquid phase separation. Studying these complex architectures remains challenging due to their conformational variability. Native mass spectrometry (nMS) is routinely employed to analyze conformations and interactions of folded or disordered proteins; however, its ability to analyze proteins with disordered LC domains has not been investigated. Here, we analyze the ionization and conformational states of designed model proteins that recapitulate key features of proteins found in membraneless organelles. Our results show that charge state distributions (CSDs) in nMS reflect partial disorder regardless of the protein sequence, providing insights into their conformational plasticity and interactions. By applying the same CSD analysis to a spider silk protein fragment, we find that interactions between folded domains that trigger silk assembly simultaneously induce conformational changes in the LC domains. Lastly, using intact nucleosomes, we demonstrate that CSDs are a good predictor for the disorder content of complex native assemblies. We conclude that nMS reliably informs about the conformational landscape of proteins with LC domains, which is crucial for understanding protein condensates in cellular environments.

The N17 domain of huntingtin as a multifaceted player in Huntington's disease.

Huntington's disease (HD) is primarily caused by the aberrant aggregation of the N-terminal exon 1 fragment of mutant huntingtin protein (mHttex1) with expanded polyglutamine (polyQ) repeats in neurons. The first 17 amino acids of the N-terminus of Httex1 (N17 domain) immediately preceding the polyQ repeat domain are evolutionarily conserved across vertebrates and play multifaceted roles in the pathogenesis of HD. Due to its amphipathic helical properties, the N17 domain, both alone and when membrane-associated, promotes mHttEx1 aggregation. Diverse post-translational modifications (PTMs) in the N17 domain alter the aggregation state, thus modulating the cellular toxicity of mHttex1. Furthermore, the N17 domain serves as a nuclear export signal (NES) and mediates the cytoplasmic localization of mHttex1. This review summarizes the four main roles of the N17 domain in regulating HD pathology and discusses potential therapeutic approaches targeting this N17 domain to mitigate HD progression.

Passaging Human Tauopathy Patient Samples in Cells Generates Heterogeneous Fibrils with a Subpopulation Adopting Disease Folds.

The discovery by cryo-electron microscopy (cryo-EM) that the neu-ropathological hallmarks of different tauopathies, including Alzheimer's disease, corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), are caused by unique misfolded conformations of the protein tau is among the most profound developments in neurodegenerative disease research. To capitalize on these discoveries for therapeutic development, one must achieve in vitro replication of tau fibrils that adopt the representative tauopathy disease folds, which represents a grand challenge for the field. A widely used approach has been seeded propagation using pathological tau fibrils derived from post-mortem patient samples in biosensor cells that expresses a fragment of the tau protein known as K18, or Tau4RD, containing the microtubule-binding repeat domain of tau as the substrate. The new insights from cryo-EM raised the question of whether the Tau4RD fragment is capable of adopting characteristic tau folds found in CBD and PSP patient fibrils, and whether cell-passaged and amplified tau fibrils can be used as seeds to achieve cell-free assembly of recombinant 4R tau into fibrils without the addition of cofactors. Using Double Electron Electron Resonance (DEER) spectroscopy, we discovered that cell-passaged pathological seeds generate heterogeneous fibrils that are, however, distinct between the CBD and PSP lysate-seeded fibrils, and vastly different from heparin-induced tau fibril structures. Moreover, the lysate-seeded fibrils contain a characteristic sub-population that resembles the disease fold corresponding to the respective starting patient sample. These findings indicate that templated propagation using CBD and PSP patient-derived fibrils is possible with a tau fragment that does not contain the entire pathological fibril core, but also that additional mechanisms must be tuned to converge on a homogeneous fibril population.

Hydrophilic interaction chromatography coupled to high resolution mass spectrometry (HILIC-LC-HRMS): An approach to study natural peptides in Viperidae snake venom.

Although proteins in snake venoms have been extensively studied and characterized, low-mass molecules remain relatively unexplored, mainly due to their low abundance, secondary role in envenomation, and some analytical technique limitations. However, these small molecules can provide new important data related to venom toxins' molecular structure, functions, and evolutionary relationships. This research aimed to characterize molecules below 10 kDa in the venoms of snakes from the Viperidae families (Bothrops, Agkistrodon, and Bitis) and compare two chromatographic approaches: reverse-phase chromatography (RP), a classic technique, and hydrophilic interaction liquid chromatography (HILIC), an alternative technique, both coupled with high-resolution mass spectrometry (HRMS). The results showed that the separation of the HILIC column provided a more efficient evenly distributed ion profile than RP, contributing to a 25.6% increase in the sequences identified. Homologous sequences for Bradykinin-potentiating peptides (BPPs) and fragments of major venom proteins, possibly cryptids, were found. In addition, BPP 13a, peptides rich in histidine and glycine (pHpG), and spacer sequences were identified in all snakes analyzed, especially with HILIC separation, suggesting that these sequences may be conserved within Viperidae. These findings indicate that the use of the HILIC column, compared to RP, is a promising approach for characterizing peptides in snake venom obtained by the ultrafiltration process. It contributes to the study of these still poorly understood molecules and is also a good option for studying other complex protein/peptide mixtures.

Bimolecular Fluorescence Complementation (BiFC) Technique for Exocytic Proteins in Murine Hippocampal Neurons.

The bimolecular fluorescence complementation (BiFC) technique is a powerful tool for visualizing protein-protein interactions in vivo. It involves genetically fused nonfluorescent fragments of green fluorescent protein (GFP) or its variants to the target proteins of interest. When these proteins interact, the GFP fragments come together, resulting in the reconstitution of a functional fluorescent protein complex that can be observed using fluorescence microscopy. In this chapter, we provide a detailed overview of the BiFC method and its application in studying protein-protein interactions in mouse hippocampal neurons. We discuss experimental procedures, including virus construct design, neuronal transduction, and imaging optimization. Additionally, we explore complementary assays for result validation and address potential challenges associated with BiFC experiments in the neuronal system. Overall, the BiFC offers researchers a valuable approach for investigating the spatial and temporal dynamics of protein interactions in living neuronal cells.

Integrated analysis of ATAC-seq and RNA-seq reveals ADSCP2 regulates oxidative phosphorylation pathway in hypertrophic scar fibroblasts.

The primary effector cells involved in the formation of hypertrophic scars are fibroblasts. A potential peptide, ADSCP2 (adipose-derived stem cell peptide 2, the peptide fragment of ALCAM protein), derived from adipose-derived stem cell-conditioned medium, has been identified as having the potential to mitigate hypertrophic scar formation by targeting pyruvate carboxylase. However, the underlying mechanisms remain incompletely understood. Whether ADSCP2 attenuates hypertrophic scar fibrosis at the transcription level remains unclear. Consequently, this study sought to elucidate the potential mechanism associated with ADSCP2 by examining genome-wide transcriptional alterations and changes in chromatin accessibility in fibroblasts. This was achieved through the integrated analysis of assay for transposase accessible chromatin using sequencing (ATAC-seq) and RNA sequencing (RNA-seq). In the ADSCP2 treatment group, ATAC-seq identified a total of 7,805 differential peaks associated with 3,176 genes. RNA-seq analysis revealed 345 upregulated and 399 downregulated transcripts in the same group. A combined Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of both downregulated genes and close-ACRs (accessible chromatin regions) genes within the ADSCP2 treatment group indicated regulation of the oxidative phosphorylation pathway (OXPHOS) by ADSCP2. The amalgamation of ATAC-seq and RNA-seq data elucidates that two OXPHOS associated genes, namely COX6B1 (cytochrome c oxidase subunit 6B1) and NDUFA1 (NADH dehydrogenase (ubiquinone) alpha subcomplex-1), demonstrate significant downregulation in the presence of ADSCP2. Further analysis using the integrative genomics viewer indicates that the promoter regions of both COX6B1 and NDUFA1 exhibit a higher degree of closure in the ADSCP2 treatment group. Quantitative PCR analysis demonstrated that ADSCP2 treatment resulted in a reduction of COX6B1 and NDUFA1 mRNA expression levels. Furthermore, cellular ATP and lactic acid concentrations were diminished in the ADSCP2-treated group. Collectively, these findings suggest potential avenues for future research into the therapeutic application of the peptide ADSCP2 in the treatment of hypertrophic scars.

Prion Protein Endoproteolysis: Cleavage Sites, Mechanisms and Connections to Prion Disease.

Highly abundant in neurons, the cellular prion protein (PrPC) is an obligatory precursor to the disease-associated misfolded isoform denoted PrPSc that accumulates in the rare neurodegenerative disorders referred to either as transmissible spongiform encephalopathies (TSEs) or as prion diseases. The ability of PrPC to serve as a substrate for this template-mediated conversion process depends on several criteria but importantly includes the presence or absence of certain endoproteolytic events performed at the cell surface or in acidic endolysosomal compartments. The major endoproteolytic events affecting PrPC are referred to as α- and β-cleavages, and in this review we outline the sites within PrPC at which the cleavages occur, the mechanisms potentially responsible and their relevance to pathology. Although the association of α-cleavage with neuroprotection is well-supported, we identify open questions regarding the importance of β-cleavage in TSEs and suggest experimental approaches that could provide clarification. We also combine findings from invitro cleavage assays and mass spectrometry-based studies of prion protein fragments in the brain to present an updated view in which α- and β-cleavages may represent two distinct clusters of proteolytic events that occur at multiple neighbouring sites rather than at single positions. Furthermore, we highlight the candidate proteolytic mechanisms best supported by the literature; currently, despite several proteases identified as capable of processing PrPC invitro, in cell-based models and in some cases, invivo, none have been shown conclusively to cleave PrPC in the brain. Addressing this knowledge gap will be crucial for developing therapeutic interventions to drive PrPC endoproteolysis in a neuroprotective direction. Finally, we end this review by briefly addressing other cleavage events, specifically ectodomain shedding, γ-cleavage, the generation of atypical pathological fragments in the familial prion disorder Gerstmann-Sträussler-Scheinker syndrome and the possibility of an additional form of endoproteolysis close to the PrPC N-terminus.

Ultrasound-assisted modification of oat protein isolates: Structural and functional enhancements.

Escalating global protein demand necessitates the commercialization of protein rich products. Oat is a promising high-quality protein source but it requires structural and functional modifications to diversify its application. The current investigation was focused on the impact of different powers of ultrasonic waves (200, 400, and 600W) on structural and functional characteristics of oat protein isolates to improve its techno-functional properties. Higher strength ultrasound waves generated flat sheet structures which were observed while analyzing microstructure of oat protein isolate (OPI). However, non-significant variation in molecular weight distribution were observed in different treatments. At 600W power of ultrasonic waves the protein fragments show local accumulation, increased α-helix content. Due to uncoiling of protein structure decrease in β-sheets and β-turns was also observed at 600W. Protein turbidity decreased significantly under low power ultrasonic treatment (200W) which significantly increased at higher power. Moderate ultrasonic treatment (400W) promoted protein dissolution, and maintained a good balance between β-sheets (71.04±0.08), α-helix (16.27±0.02) and β-turns (12.68±0.03), exhibiting optimized flexibility and structural integrity. Whereas, higher strength (600W) significantly destroyed protein structure. The amino acid content decreased significantly with increasing ultrasonic power. The thermal characteristics of OPI remained unaffected after ultrasound treatment. In conclusion, modifications of secondary and tertiary structure induced by moderate ultrasonic treatment (400W) improved functional properties of OPI. The 400W treatment resulted in highest essential amino acid content (EAA) i.e., 22.75±0.82mg/100mg and total amino acid content (TAA) i.e., 64.94±2.7mg/100mg, which are significantly higher than WHO and FAO standards, suggesting best total and essential amino acid production in comparison to other treatments.

Efficient production of recombinant hybrid mussel proteins with improved adhesion.

Mussel foot proteins (mfps) play important roles in surface interaction and underwater adhesion. However, limited production and the lack of adhesion of recombinant mfps have restricted their widespread use. Here, we present a general strategy for enhancing both the expression and function of mfps by connecting multiple protein fragments. We demonstrate that fp-535, the fusion protein comprising fp-5 at each fp-3 terminus, exhibits best adhesion strength up to 1.43 MPa and coating ability, while achieving a higher yield of 91.13 mg/L in the flask culture. After optimizing the fermentation parameters such as temperature and volume as well as the culture medium, the yield of fp-535 was increased to 1.70 g/L in a 5-L bioreactor. Our approach highlights the advantage of fusion mfps and provides potential for the sustainable supply of practical bioadhesive materials.