Amino Acid Sequence Motifs Research Articles

Identification and characterization of two selenium-dependent glutathione peroxidase 1 isoforms from Larimichthys crocea

Glutathione peroxidases, a vital family of antioxidant enzymes in oxybiotic organisms, are involved in anti-pathogen immune response. In this study, two complete selenium-dependent glutathione peroxidase 1 cDNAs (designated as LcGPx1a and LcGPx1b) were obtained from the large yellow croaker Larimichthys crocea by rapid amplification of cDNA ends. The full-length sequence of LcGPx1a was 917 bp with a 5′-untranslated region (UTR) of 52 bp, a 3′-UTR of 289 bp, and an open reading frame of 576 bp encoding 191 amino acid (aa) polypeptides. The cDNA of LcGPx1b was composed of 884 bp with a 5′-UTR of 59 bp, a 3′-UTR of 258 bp, and an open reading frame of 567 bp encoding 188 aa polypeptides. The conserved selenocysteine insertion sequence was detected in the 3′-UTR of both isoforms, which can classify types I and II. Protein sequence analysis revealed that both isoforms included a selenocysteine encoded by an opal codon (TGA) and formed the functioning tetrad site with glutamine, tryptophan, and asparagine. Three conservative motifs, including one active site motif (“GKVVLIENVASLUGTT”) and two signature site motifs (“LVILGVPCNQFGHQENC” and “V(A/S)WNFEKFLI”), were conserved both in sequence and location. Multiple alignments revealed that they exhibited a high level of identities with GPx1 from other organisms, especially in the abovementioned conserved amino acid sequence motifs. Tissue expression analysis indicated that LcGPx1a and LcGPx1b had a wide distribution in nine tissues with various abundances. The transcript level of LcGPx1a was not significantly different among the nine tissues, whereas that of LcGPx1b was higher in the kidney and head kidney than in the other tissues. After Vibrio parahaemolyticus stimulation, the expression levels of LcGPx1a and LcGPx1b were unanimously altered in the liver, spleen, kidney, and head kidney but with different magnitudes and response time. LcGPx1a and LcGPx1b showed distinct expression trends in the liver, where LcGPx1b was induced and LcGPx1a was depressed in response to pathogen infection. These results indicate that LcGPx1a and LcGPx1b display functional diversities and play crucial roles in mediating the immune response of fish.

Self-Organizing Map for Characterizing Heterogeneous Nucleotide and Amino Acid Sequence Motifs

A self-organizing map (SOM) is an artificial neural network algorithm that can learn from the training data consisting of objects expressed as vectors and perform non-hierarchical clustering to represent input vectors into discretized clusters, with vectors assigned to the same cluster sharing similar numeric or alphanumeric features. SOM has been used widely in transcriptomics to identify co-expressed genes as candidates for co-regulated genes. I envision SOM to have great potential in characterizing heterogeneous sequence motifs, and aim to illustrate this potential by a parallel presentation of SOM with a set of numerical vectors and a set of equal-length sequence motifs. While there are numerous biological applications of SOM involving numerical vectors, few studies have used SOM for heterogeneous sequence motif characterization. This paper is intended to encourage (1) researchers to study SOM in this new domain and (2) computer programmers to develop user-friendly motif-characterization SOM tools for biologists.

A Unique T-Cell Receptor Amino Acid Sequence Selected by Human T-Cell Lymphotropic Virus Type 1 Tax 301-309 -Specific Cytotoxic T Cells in HLA-A24:02-Positive Asymptomatic Carriers and Adult T-Cell Leukemia/Lymphoma Patients

We previously reported that the T-cell receptor (TCR) repertoire of human T-cell lymphotropic virus type 1 (HTLV-1) Tax301-309-specific CD8+ cytotoxic T cells (Tax301-309-CTLs) was highly restricted and a particular amino acid sequence motif, the PDR motif, was conserved among HLA-A*24:02-positive (HLA-A*24:02+) adult T-cell leukemia/lymphoma (ATL) patients who had undergone allogeneic hematopoietic cell transplantation (allo-HSCT). Furthermore, we found that donor-derived PDR+ CTLs selectively expanded in ATL long-term HSCT survivors with strong CTL activity against HTLV-1. On the other hand, the TCR repertoires in Tax301-309-CTLs of asymptomatic HTLV-1 carriers (ACs) remain unclear. In this study, we directly identified the DNA sequence of complementarity-determining region 3 (CDR3) of the TCR-β chain of Tax301-309-CTLs at the single-cell level and compared not only the TCR repertoires but also the frequencies and phenotypes of Tax301-309-CTLs between ACs and ATL patients. We did not observe any essential difference in the frequencies of Tax301-309-CTLs between ACs and ATL patients. In the single-cell TCR repertoire analysis of Tax301-309-CTLs, 1,458 Tax301-309-CTLs and 140 clones were identified in this cohort. Tax301-309-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was exclusively observed in all ACs and ATL patients. However, there was no correlation between PDR+ CTL frequencies and HTLV-1 proviral load (PVL). In conclusion, we have identified, for the first time, a unique amino acid sequence, PDR, as a public TCR-CDR3 motif against Tax in HLA-A*24:02+ HTLV-1-infected individuals. Further investigations are warranted to elucidate the role of the PDR+ CTL response in the progression from carrier state to ATL.IMPORTANCE ATL is an aggressive T-cell malignancy caused by HTLV-1 infection. The HTLV-1 regulatory protein Tax aggressively promotes the proliferation of HTLV-1-infected lymphocytes and is also a major target antigen for CD8+ CTLs. In our previous evaluation of Tax301-309-CTLs, we found that a unique amino acid sequence motif, PDR, in CDR3 of the TCR-β chain of Tax301-309-CTLs was conserved among ATL patients after allo-HSCT. Furthermore, the PDR+ Tax301-309-CTL clones selectively expanded and showed strong cytotoxic activities against HTLV-1. On the other hand, it remains unclear how Tax301-309-CTL repertoire exists in ACs. In this study, we comprehensively compared Tax-specific TCR repertoires at the single-cell level between ACs and ATL patients. Tax301-309-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was conserved in all ACs and ATL patients, regardless of clinical subtype in HTLV-1 infection.

Abstract 3767: Identification of a novel and a shared H3.3K27M mutation derived neoantigen epitope and H3.3K27M specific TCR engineered T cell therapy for glioma

Abstract Brain cancers are the leading cause of cancer related mortality in children and young adults with median overall survival of 9-10 months and hence represents a significant unmet medical need. Genome-wide sequencing efforts of pediatric gliomas have identified a recurrent and shared missense mutation in the gene encoding the replication-independent variant of histone 3, H3.3. Approximately 70% of diffuse intrinsic pontine gliomas (DIPG) and 50% of thalamic and other midline gliomas harbor the amino acid substitution from lysine (K) to methionine (M) at the position 27 of H3.3 gene. Tumor specific missense mutations are not subjected to self-tolerance and can be suitable targets (neoantigens) for cancer immunotherapy. Herein, we evaluated whether the H3.3K27M mutation can induce specific cytotoxic T lymphocyte (CTL) response in HLA-A2+ T cells. In vitro stimulation of HLA-A2+ donor derived CD8+ T cells with a synthetic peptide encompassing the H3.3K27M mutation (H3.3K27M epitope) induced CTL lines which recognized not only T2 cells loaded with the synthetic H3.3K27M epitope peptide but also lysed the HLA-A2+ DIPG cells which endogenously harbor the H3.3K27M mutation. On the other hand, the CTL lines did not react to either HLA-A2+ but H3.3K27M- negative DIPG cell lines or H3.3K27M positive but HLA-A2 negative DIPG cells. The H3.3K27M epitope peptide but not the non-mutant counterpart indicated an excellent binding affinity (Kd 151nM) to HLA-A2 based on competitive binding inhibition assay. From CTL clones with high and specific affinities to HLA-A2-H3.3K27M-tetramer, cDNAs for T cell receptor (TCR) alpha and beta chains were cloned into a retroviral vector. Human HLA-A2+ T cells transduced with the TCR demonstrated antigen specific reactivity as well as anti-glioma responses in vitro. Peptide titration assays suggested that the H3.3K27M specific TCR had the half-maximal reactivity for peptide recognition of around 100nM. Furthermore, critically important for safety of clinical application, alanine scanning demonstrated that the key amino acid sequence motif in the epitope of the TCR reactivity is not shared by any known human protein. Finally, intravenous administration of T cells transduced with H3.3K27M specific TCR significantly inhibited the growth of intracranial HLA-A2+ H3.3K27M positive glioma xenografts in immune deficient NSG mice. These data provide us with a strong basis for developing peptide based vaccines as well as adoptive transfer therapy using autologous T cells transduced with the H3.3K27M specific TCR. Acknowledgements: This study is supported by the NIH/NINDS (1RO1NS096954), V Foundation and Parker Institution for Cancer Immunotherapy. Citation Format: Zinal Chheda, Gary Kohanbash, John Sidney, Kaori Okada, Naznin Jahan, Diego Carrera, Payal Watchmaker, Kira Downey, Shuming Liu, Shruti Shrivastav, Sabine Mueller, Ian F. Pollack, Angel M. Carcaboso, Alessandro Sette, Yafei Hou, Hideho Okada. Identification of a novel and a shared H3.3K27M mutation derived neoantigen epitope and H3.3K27M specific TCR engineered T cell therapy for glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3767. doi:10.1158/1538-7445.AM2017-3767

Prediction of bioluminescent proteins by using sequence-derived features and lineage-specific scheme

BackgroundBioluminescent proteins (BLPs) widely exist in many living organisms. As BLPs are featured by the capability of emitting lights, they can be served as biomarkers and easily detected in biomedical research, such as gene expression analysis and signal transduction pathways. Therefore, accurate identification of BLPs is important for disease diagnosis and biomedical engineering. In this paper, we propose a novel accurate sequence-based method named PredBLP (Prediction of BioLuminescent Proteins) to predict BLPs.ResultsWe collect a series of sequence-derived features, which have been proved to be involved in the structure and function of BLPs. These features include amino acid composition, dipeptide composition, sequence motifs and physicochemical properties. We further prove that the combination of four types of features outperforms any other combinations or individual features. To remove potential irrelevant or redundant features, we also introduce Fisher Markov Selector together with Sequential Backward Selection strategy to select the optimal feature subsets. Additionally, we design a lineage-specific scheme, which is proved to be more effective than traditional universal approaches.ConclusionExperiment on benchmark datasets proves the robustness of PredBLP. We demonstrate that lineage-specific models significantly outperform universal ones. We also test the generalization capability of PredBLP based on independent testing datasets as well as newly deposited BLPs in UniProt. PredBLP is proved to be able to exceed many state-of-art methods. A web server named PredBLP, which implements the proposed method, is free available for academic use.

OS09.4 Identification of a novel H3.3.K27M mutation-derived neoantigen epitope and cloning of H3.3.K27M-specific T-cell receptor for T-cell therapy in gliomas

Brain cancers are the leading cause of cancer related mortality and morbidity in children and young adults. Children with diffuse intrinsic brainstem malignant gliomas have one-year progression-free survival rates below 25% and median overall survival of 9 to 10 months with current treatment options and hence represent a significant unmet medical need. Genome-wide sequencing efforts of pediatric gliomas have identified a recurrent and shared missense mutation in the gene encoding the replication-independent variant of histone 3, H3.3. Approximately 70% of diffuse intrinsic pontine gliomas (DIPG) and 50% of thalamic and other midline gliomas harbor the amino-acid substitution from lysine (K) to methionine (M) at the position 27 of H3.3 gene (H3.3.K27M mutation). Tumor-specific missense mutations are not subjected to self-tolerance and can be suitable targets (i.e. neoantigen) for cancer immunotherapy. We evaluated whether the H3.3.K27M mutation can induce specific cytotoxic T lymphocyte (CTL) response in HLA-A2+ human T cells. In vitro stimulation of HLA-A2+ donor-derived CD8+ T-cells with a synthetic peptide encompassing the H3.3.K27M mutation (H3.3.K27M epitope) induced CTL lines which recognized not only T2 cells loaded with the synthetic H3.3.K27M epitope peptide but also lysed HLA-A2+ DIPG cell lines which endogenously harbor the H3.3.K27M mutation. On the other hand, the CTL lines did not react to either HLA-A2+ H3.3.K27M -negative DIPG cell lines or H3.3K27M-positive but HLA-A2-negative cells. The H3.3.K27M epitope peptide, but not the non-mutant counterpart, indicated an excellent affinity (Kd 151nM) to HLA-A2 based on competitive binding inhibition assay. From CTL clones with high and specific affinities to HLA-A2-H3.3.K27M-tetramer, cDNAs for T cell receptor (TCR) α- and β-chains were cloned into a retroviral vector. Human HLA-A2+ T-cells transduced with the TCR demonstrated antigen-specific reactivity as well as anti-glioma responses in vitro. Peptide titration assay suggested that the H3.3.K27M-specific TCR had the half-maximal reactivity for peptide recognition of around 100nM. Furthermore, critically important for safety of clinical application, alanine scanning demonstrated that the key amino-acid sequence motif in the epitope for the TCR reactivity is not shared by any known human protein. Finally, intravenous administration of T-cells transduced with the H3.3.K27M-specific TCR significantly inhibited the growth of intracranial HLA-A2+ H3.3.K27M-positive glioma xenografts in immune-deficient mice. These data provide us with a strong basis for developing peptide-based vaccines as well as adoptive transfer therapy using autologous T-cells transduced with the H3.3.K27M-specific TCR.

Ion and inhibitor binding of the double-ring ion selectivity filter of the mitochondrial calcium uniporter

The calcium (Ca2+) uniporter of mitochondria is a holocomplex consisting of the Ca2+-conducting channel, known as mitochondrial calcium uniporter (MCU), and several accessory and regulatory components. A previous electrophysiology study found that the uniporter has high Ca2+ selectivity and conductance and this depends critically on the conserved amino acid sequence motif, DXXE (Asp-X-X-Glu) of MCU. A recent NMR structure of the MCU channel from Caenorhabditis elegans revealed that the DXXE forms two parallel carboxylate rings at the channel entrance that seem to serve as the ion selectivity filter, although direct ion interaction of this structural motif has not been addressed. Here, we use a paramagnetic probe, manganese (Mn2+), to investigate ion and inhibitor binding of this putative selectivity filter. Our paramagnetic NMR data show that mutants with a single carboxylate ring, NXXE (Asn-X-X-Glu) and DXXQ (Asp-X-X-Gln), each can bind Mn2+ specifically, whereas in the WT the two rings bind Mn2+ cooperatively, resulting in ∼1,000-fold higher apparent affinity. Ca2+ can specifically displace the bound Mn2+ at the DXXE site in the channel. Furthermore, titrating the sample with the known channel inhibitor ruthenium 360 (Ru360) can displace Mn2+ binding from the solvent-accessible Asp site but not the inner Glu site. The NMR titration data, together with structural analysis of the DXXE motif and molecular dynamics simulation, indicate that the double carboxylate rings at the apex of the MCU pore constitute the ion selectivity filter and that Ru360 directly blocks ion entry into the filter by binding to the outer carboxylate ring.

Cloning and molecular characterization of the betaine aldehyde dehydrogenase involved in the biosynthesis of glycine betaine in white shrimp (Litopenaeus vannamei)

The enzyme betaine aldehyde dehydrogenase (BADH) catalyzes the irreversible oxidation of betaine aldehyde to glycine betaine (GB), a very efficient osmolyte accumulated during osmotic stress. In this study, we determined the nucleotide sequence of the cDNA for the BADH from the white shrimp Litopenaeus vannamei (LvBADH). The cDNA was 1882 bp long, with a complete open reading frame of 1524 bp, encoding 507 amino acids with a predicted molecular mass of 54.15 kDa and a pI of 5.4. The predicted LvBADH amino acid sequence shares a high degree of identity with marine invertebrate BADHs. Catalytic residues (C-298, E-264 and N-167) and the decapeptide VTLELGGKSP involved in nucleotide binding and highly conserved in BADHs were identified in the amino acid sequence. Phylogenetic analyses classified LvBADH in a clade that includes ALDH9 sequences from marine invertebrates. Molecular modeling of LvBADH revealed that the protein has amino acid residues and sequence motifs essential for the function of the ALDH9 family of enzymes. LvBADH modeling showed three potential monovalent cation binding sites, one site is located in an intra-subunit cavity; other in an inter-subunit cavity and a third in a central-cavity of the protein. The results show that LvBADH shares a high degree of identity with BADH sequences from marine invertebrates and enzymes that belong to the ALDH9 family. Our findings suggest that the LvBADH has molecular mechanisms of regulation similar to those of other BADHs belonging to the ALDH9 family, and that BADH might be playing a role in the osmoregulation capacity of L. vannamei.

Direct Observation of Unidirectional Cholesterol Flipping on the Surface of P-Glycoprotein

P-glycoprotein (Pgp) is a biomedically important member of the largest superfamily of ABC transporters and mediates multidrug resistance in many cancer types. Substrate binding and transport in Pgp are modulated by the presence of cholesterol in the membrane, while cholesterol itself is a substrate and exported by Pgp. Structural information on cholesterol binding sites and mechanistic details of its transport pathway are largely unknown. In this study, a set of 35 independent simulations of Pgp oriented independently in cholesterol-rich lipid bilayers were performed, adding to a total of 7 μs, enabling extensive sampling of lipid-protein interactions. From the ensemble of cholesterol molecules (∼4700) sampled in these simulations, one complete and two partial cholesterol flipping events were captured. All of the flipping events visited a region formed by transmembrane (TM) helices TM1, TM2, and TM11 with Tyr 49 and Tyr 126 as key residues interacting with cholesterol. This region has been identified with two cholesterol-recognition amino acid sequence (CRAC) motifs. Cholesterol flipping from the inner leaflet initially binds to this motif and assumes a 90° angle to the membrane normal burying its only hydroxyl group within the surface of the protein followed by flipping to the outer leaflet. Convergence and clustering analyses of cholesterol molecules around Pgp revealed that cholesterol binds to specific regions formed between TM1-6 and TM8 helices interacting through its rough surface. From the generated ensemble of cholesterol sampling around Pgp, only a single complete cholesterol flipping from inner leaflet to outer leaflet has been directly observed, which supports the known flippase activity of Pgp. Our study is the first to report that substrate translocation by Pgp might take place through pathways on the surface of the protein.

Pore Architecture and Ion Selectivity Filter of the Mitochondrial Calcium Uniporter

The calcium uniporter of mitochondria is a holocomplex consisting of the calcium-conducting channel, known as the MCU channel, and a score of regulatory proteins. Previous electrophysiology study found that a preeminent property of the uniporter is the high calcium selectivity and conductance and this has been shown to critically depend on the highly conserved amino acid sequence motif, DXXE, in the MCU channel. Our recent NMR data of the MCU channel indicate that the DXXE forms two parallel carboxylate rings at the channel entrance that appear to serve as the ion selectivity filter. We used paramagnetic probes to show that mutants with a single carboxylate ring can bind divalent cation specifically, while in the wild type, the two rings bind the ion cooperatively, resulting in drastically higher apparent affinity. Our new data, together with structural analysis of the DXXE motif, indicate that the double carboxylate rings at the apex of the MCU pore constitute the ion selectivity filter of the channel and that Ru360 directly blocks ion entry into the filter.

Screening, purification, and characterization of a novel organic solvent-tolerant esterase, Lip2, from Monascus purpureus strain M7.

Organic solvent-tolerant esterases are proven to be excellent biocatalysts in chemical and pharmaceutical industries. A novel organic solvent-tolerant esterase gene, lip2, was isolated from filamentous fungi Monascus purpureus M7. The sequence analysis suggested that lip2 has a conserved "GDSL" motif near the active center. The multiple-sequence alignment and phylogenetic analysis revealed that Lip2 displayed two unique amino-acid sequence motifs that clearly separate it from any other previously described lipase family. After incubation in 20% methanol and ethanol for 3h, the Lip2 displayed 190 and 180% residual activities, respectively. It retained 99-110% relative activity in 20% (v/v) hydrophilic organic solvents after incubation for 1day. This esterase showed optimal activity at 40 °C and retained about 70% maximal activity at 60 °C. The enzyme also displayed more than 50% residual activity over a range of pH 5-11. In the presence of most of metal ions or additives, Lip2 retained most of the activity. These unique properties of Lip2 make it a promising as biocatalyst for industrial processes.

Complete gene sequence of spider attachment silk protein (PySp1) reveals novel linker regions and extreme repeat homogenization

Spiders use a myriad of silk types for daily survival, and each silk type has a unique suite of task-specific mechanical properties. Of all spider silk types, pyriform silk is distinct because it is a combination of a dry protein fiber and wet glue. Pyriform silk fibers are coated with wet cement and extruded into “attachment discs” that adhere silks to each other and to substrates. The mechanical properties of spider silk types are linked to the primary and higher-level structures of spider silk proteins (spidroins). Spidroins are often enormous molecules (>250 kDa) and have a lengthy repetitive region that is flanked by relatively short (∼100 amino acids), non-repetitive amino- and carboxyl-terminal regions. The amino acid sequence motifs in the repetitive region vary greatly between spidroin type, while motif length and number underlie the remarkable mechanical properties of spider silk fibers. Existing knowledge of pyriform spidroins is fragmented, making it difficult to define links between the structure and function of pyriform spidroins. Here, we present the full-length sequence of the gene encoding pyriform spidroin 1 (PySp1) from the silver garden spider Argiope argentata. The predicted protein is similar to previously reported PySp1 sequences but the A. argentata PySp1 has a uniquely long and repetitive “linker”, which bridges the amino-terminal and repetitive regions. Predictions of the hydrophobicity and secondary structure of A. argentata PySp1 identify regions important to protein self-assembly. Analysis of the full complement of A. argentata PySp1 repeats reveals extreme intragenic homogenization, and comparison of A. argentata PySp1 repeats with other PySp1 sequences identifies variability in two sub-repetitive expansion regions. Overall, the full-length A. argentata PySp1 sequence provides new evidence for understanding how pyriform spidroins contribute to the properties of pyriform silk fibers.

A reciprocal HLA-Disease Association in Rheumatoid Arthritis and Pemphigus Vulgaris.

Human leukocyte antigens (HLA) have been extensively studied as being antigen presenting receptors, but many aspects of their function remain elusive, especially their association with various autoimmune diseases. Here we discuss an illustrative case of the reciprocal relationship between certain HLA-DRB1 alleles and two diseases, rheumatoid arthritis (RA) and pemphigus vulgaris (PV). RA is strongly associated with HLA-DRB1 alleles that encode a five amino acid sequence motif in the 70-74 region of the DR beta chain, called the shared epitope (SE), while PV is associated with the HLA-DRB1*04:02 allele that encodes a different sequence motif in the same region. Interestingly, while HLA-DRB1*04:02 confers susceptibility to PV, this and other alleles that encode the same sequence motif in the 70-74 region of the DR beta chain are protective against RA. Currently, no convincing explanation for this antagonistic effect is present. Here we briefly review the immunology and immunogenetics of both diseases, identify remaining gaps in our understanding of their association with HLA, and propose the possibility that the 70-74 DR beta epitope may contribute to disease risk by mechanisms other than antigen presentation.

Molecular characterization of XopAG effector AvrGf2 from Xanthomonas fuscans ssp. aurantifolii in grapefruit.

Xanthomonas fuscans ssp. aurantifolii group C strains exhibit host specificity on different citrus species. The strains possess a type III effector, AvrGf2, belonging to the XopAG effector gene family, which restricts host range on citrus. We dissected the modular nature and mode of action of AvrGf2 in grapefruit resistance. XopAG effectors possess characteristic features, such as a chloroplast localization signal, a cyclophilin-binding domain characteristic amino acid sequence motif (GPLL) and a C-terminal domain-containing CLNAxYD. Mutation of GPLL to AASL in AvrGf2 abolished the elicitation of the hypersensitive response (HR), whereas mutation of only the first amino acid to SPLL delayed the HR in grapefruit. Yeast two-hybrid experiments showed strong interaction of AvrGf2 with grapefruit cyclophilin (GfCyp), whereas AvrGf2-SPLL and AvrGf2-AASL mutants showed weak and no interaction, respectively. Molecular modelling and insilico docking studies for the cyclophilin-AvrGf2 interaction predicted the binding of citrus cyclophilins (CsCyp, GfCyp) to hexameric peptides spanning the cyclophilin-binding domain of AvrGf2 and AvrGf2 mutants (VAGPLL, VASPLL and VAAASL) with affinities equivalent to or better than a positive control peptide (YSPSA) previously demonstrated to bind CsCyp. In addition, the C-terminal domain of XopAG family effectors contains a highly conserved motif, CLNAxYD, which was identified to be crucial for the induction of HR based on site-directed mutagenesis (CLNAxYD to CASAxYD). Our results suggest a model in which grapefruit cyclophilin promotes a conformational change in AvrGf2, thereby triggering the resistance response.

The early history and emergence of molecular functions and modular scale-free network behavior.

The formation of protein structural domains requires that biochemical functions, defined by conserved amino acid sequence motifs, be embedded into a structural scaffold. Here we trace domain history onto a bipartite network of elementary functional loop sequences and domain structures defined at the fold superfamily level of SCOP classification. The resulting ‘elementary functionome’ network and its loop motif and structural domain graph projections create evolutionary ‘waterfalls’ describing the emergence of primordial functions. Waterfalls reveal how ancient loops are shared by domain structures in two initial waves of functional innovation that involve founder ‘p-loop’ and ‘winged helix’ domain structures. They also uncover a dynamics of modular motif embedding in domain structures that is ongoing, which transfers ‘preferential’ cooption properties of ancient loops to emerging domains. Remarkably, we find that the emergence of molecular functions induces hierarchical modularity and power law behavior in network evolution as the network of motifs and structures expand metabolic pathways and translation.

Transcriptomics-based identification of WRKY genes and characterization of a salt and hormone-responsive PgWRKY1 gene in Panax ginseng.

WRKY proteins belong to a transcription factor (TF) family and play dynamic roles in many plant processes, including plant responses to abiotic and biotic stresses, as well as secondary metabolism. However, no WRKY gene in Panax ginseng C.A. Meyer has been reported to date. In this study, a number of WRKY unigenes from methyl jasmonate (MeJA)-treated adventitious root transcriptome of this species were identified using next-generation sequencing technology. A total of 48 promising WRKY unigenes encoding WRKY proteins were obtained by eliminating wrong and incomplete open reading frame (ORF). Phylogenetic analysis reveals 48 WRKY TFs, including 11 Group I, 36 Group II, and 1 Group III. Moreover, one MeJA-responsive unigene designated as PgWRKY1 was cloned and characterized. It contains an entire ORF of 1077 bp and encodes a polypeptide of 358 amino acid residues. The PgWRKY1 protein contains a single WRKY domain consisting of a conserved amino acid sequence motif WRKYGQK and a C2H2-type zinc-finger motif belonging to WRKY subgroup II-d. Subcellular localization of PgWRKY1-GFP fusion protein in onion and tobacco epidermis cells revealed that PgWRKY1 was exclusively present in the nucleus. Quantitative real-time polymerase chain reaction analysis demonstrated that the expression of PgWRKY1 was relatively higher in roots and lateral roots compared with leaves, stems, and seeds. Importantly, PgWRKY1 expression was significantly induced by salicylic acid, abscisic acid, and NaCl, but downregulated by MeJA treatment. These results suggested that PgWRKY1 might be a multiple stress-inducible gene responding to hormones and salt stresses.

Sự lưu hành và biến đổi di truyền của virus cúm gia cầm Type A H5N1 trên gia cầm tại một số tỉnh Đồng bằng sông Cửu Long

Avian influenza disease is an acute infectious disease of avian caused by Orthomyxoviridae virus. The present study on the circulation and genetic variation of type A H5N1 avian influenza virus in Hau Giang, Soc Trang, Tra Vinh and Vinh Long provinces has been conducted by sampling swabs on poultry (healthy chicken and duck) trading at live bird market or slaughterhouses. The swab samples were tested using Real time RT-PCR technique to identify type A H5N1 avian influenza virus and to define the rate of prevalence and further implement HA gene sequencing for determination of genetic variation and clade. It was shown that the average prevalence of type A H5N1 avian influenza virus on poultry in above provinces in the Mekong delta was 6,5% whereas the prevalence of type A H5N1 avian influenza virus on duck and chicken was 9,7% and 4%, respectively. Besides, results of genetic variation investigation showed that nucleotide differentiation between circulating strains in the provinces and the reference strain A/Hong Kong/6841/2010 was from 2.3 – 3.2% . The amino acid sequence motif at connecting position between HA1 and HA2 segment was Q-ERRRKR-G and similar to the sequence of reference strain A/Hong Kong/6841/2010. The strains of type A H5N1 avian influenza virus circulating in the provinces of Hau Giang, Soc Trang, Tra Vinh and Vinh Long belong to virus clade of 2.3.2.1c.

Expression of the invertebrate sea urchin P16 protein into mammalian MC3T3 osteoblasts transforms and reprograms them into "osteocyte-like" cells.

P16 is an acidic phosphoprotein important in both sea urchin embryonic spicule development and transient mineralization during embryogenesis, syncytium formation, and mineralization in mature urchin tooth. Anti-P16 has been used to localize P16 to the syncytial membranes and the calcite mineral. Specific amino acid sequence motifs in P16 are similar to sequences in DSPP, a protein common to all vertebrate teeth, and crucial for their mineralization. Here, we examine the effect of P16 on vertebrate fibroblastic NIH3T3 cells and osteoblastic MC3T3 cells. Transfection of NIH3T3 cells with P16 cDNA resulted in profound changes in the morphology of the cells. In culture, the transfected cells sent out long processes that contacted processes from neighboring cells forming networks or syncytia. There was a similar change in morphology in cultured osteoblastic MC3T3 cells. In addition, the MC3T3 developed numerous dendrites as found in osteocytes. Importantly, there was also a change in the expression of the osteoblast and osteocyte specific genes. MC3T3 cells transfected with P16 showed an 18-fold increase in expression of the osteocyte specific Dentin matrix protein (DMP1) gene, accompanied by decreased expression of osteoblast specific genes: Bone sialoprotein (BSP), osteocalcin (OCN), and β-catenin decreased by 70%, 64%, and 68 %, respectively. Thus, invertebrate urchin P16 with no previously known analog in vertebrates was able to induce changes in both cell morphology and gene expression, converting vertebrate-derived osteoblast-like precursor cells to an "osteocyte-like" phenotype, an important process in bone biology. The mechanisms involved are presently under study.

Of ITIMs, ITAMs, and ITAMis: revisiting immunoglobulin Fc receptor signaling.

Receptors for immunoglobulin Fc regions play multiple critical roles in the immune system, mediating functions as diverse as phagocytosis, triggering degranulation of basophils and mast cells, promoting immunoglobulin class switching, and preventing excessive activation. Transmembrane signaling associated with these functions is mediated primarily by two amino acid sequence motifs, ITAMs (immunoreceptor tyrosine-based activation motifs) and ITIMs (immunoreceptor tyrosine-based inhibition motifs) that act as the receptors' interface with activating and inhibitory signaling pathways, respectively. While ITAMs mobilize activating tyrosine kinases and their consorts, ITIMs mobilize opposing tyrosine and inositol-lipid phosphatases. In this review, we will discuss our current understanding of signaling by these receptors/motifs and their sometimes blurred lines of function.

Repeat-containing protein effectors of plant-associated organisms.

Many plant-associated organisms, including microbes, nematodes, and insects, deliver effector proteins into the apoplast, vascular tissue, or cell cytoplasm of their prospective hosts. These effectors function to promote colonization, typically by altering host physiology or by modulating host immune responses. The same effectors however, can also trigger host immunity in the presence of cognate host immune receptor proteins, and thus prevent colonization. To circumvent effector-triggered immunity, or to further enhance host colonization, plant-associated organisms often rely on adaptive effector evolution. In recent years, it has become increasingly apparent that several effectors of plant-associated organisms are repeat-containing proteins (RCPs) that carry tandem or non-tandem arrays of an amino acid sequence or structural motif. In this review, we highlight the diverse roles that these repeat domains play in RCP effector function. We also draw attention to the potential role of these repeat domains in adaptive evolution with regards to RCP effector function and the evasion of effector-triggered immunity. The aim of this review is to increase the profile of RCP effectors from plant-associated organisms.