Protein identification and analysis tools in the ExPASy server

Comprehensive analysis of AHL gene family and their expression under drought stress and ABA treatment in Populus trichocarpa

The AT-hook motif nuclear-localized (AHL) family is a plant transcription factor family, which plays an important role in growth and development and stress responses. We identified and analyzed 37 AHL genes in poplar (Populus trichocarpa). Phylogenetic analysis classified the PtrAHL members into three subfamilies based on their conserved domain. All PtrAHL paralogous pairs evolved under purifying selection. The promoter analysis revealed the presence of stress-related and phytohormone-related cis-elements of the PtrAHL genes. Our analysis of the tissue-specific expression pattern of PtrAHL genes indicated their significance in tissue and organ development. Network-based prediction suggested that PtrAHL genes may interact with histone deacetylases (HDAC) and participate in the development of organs, such as roots. Drought negatively impacts plant growth and development. ABA is produced under osmotic stress condition, and it takes an important part in the stress response and tolerance of plants. Real-time quantitative PCR (qRT-PCR) showed that PtrAHL genes were induced by drought stress and ABA treatment. These insights into the expression of PtrAHL genes under stress provide a basis for PtrAHL gene functional analysis. Our study will help develop new breeding strategies to improve drought tolerance in poplar.

Implementation of in silico methods to predict common epitopes for vaccine development against Chikungunya and Mayaro viruses

Being a Positive sense RNA virus the recent reemergence of Chikungunya and Mayaro virus has taken the concern of the leading scientific communities of the world. Though the outbreak of Mayaro virus is limited to Neotropical region only, Chikungunya is already identified in over 60 countries around the world. Besides, the lack of a strong protective treatment, misdiagnosis issue and co-circulation of both the viruses calls for a new strategy which could potentially prevent these infections from spreading. In this study, we therefore, identified the peptide based vaccine candidates e.g. epitopes for B cell and T cell from Chikungunya virus which also showed to be homologous to the Mayaro virus through immuno-informatics and computational approaches. Final epitopes identified from the most antigenic structural polyprotein of both the viruses were 5 for CD8+ T cell Epitopes (209KPGDSGRPI217, 219TGTMGHFIL227, 239ALSVVTWNK247, 98KPGRRERMC106 and 100GRRERMCMK108), 2 epitopes for CD4+ T cell (105MCMKIENDCIFEVKH119 and 502DRTLLSQQSGNVKIT516) and a single epitope for B cell (504GGRFTIPTGAGKPGDSGRPI518). Analysis of our predicted epitopes for population coverage showed prominent population coverage (92.43%) around the world. Finally, molecular docking simulation of the foreseen T cell epitopes with respondent HLA alleles secured good HLA-epitope interaction. This study was directed towards the discovery of potential antigenic epitopes which can open up a new skyline to design novel vaccines for combating both of the diseases at the same time.

Immunoinformatics and Molecular Docking Studies Predicted Potential Multiepitope-Based Peptide Vaccine and Novel Compounds against Novel SARS-CoV-2 through Virtual Screening

BACKGROUND

Coronaviruses (CoVs) are enveloped positive-strand RNA viruses which have club-like spikes at the surface with a unique replication process. Coronaviruses are categorized as major pathogenic viruses causing a variety of diseases in birds and mammals including humans (lethal respiratory dysfunctions). Nowadays, a new strain of coronaviruses is identified and named as SARS-CoV-2. Multiple cases of SARS-CoV-2 attacks are being reported all over the world. SARS-CoV-2 showed high death rate; however, no specific treatment is available against SARS-CoV-2.

METHODS

In the current study, immunoinformatics approaches were employed to predict the antigenic epitopes against SARS-CoV-2 for the development of the coronavirus vaccine. Cytotoxic T-lymphocyte and B-cell epitopes were predicted for SARS-CoV-2 coronavirus protein. Multiple sequence alignment of three genomes (SARS-CoV, MERS-CoV, and SARS-CoV-2) was used to conserved binding domain analysis.

RESULTS

The docking complexes of 4 CTL epitopes with antigenic sites were analyzed followed by binding affinity and binding interaction analyses of top-ranked predicted peptides with MHC-I HLA molecule. The molecular docking (Food and Drug Regulatory Authority library) was performed, and four compounds exhibiting least binding energy were identified. The designed epitopes lead to the molecular docking against MHC-I, and interactional analyses of the selected docked complexes were investigated. In conclusion, four CTL epitopes (GTDLEGNFY, TVNVLAWLY, GSVGFNIDY, and QTFSVLACY) and four FDA-scrutinized compounds exhibited potential targets as peptide vaccines and potential biomolecules against deadly SARS-CoV-2, respectively. A multiepitope vaccine was also designed from different epitopes of coronavirus proteins joined by linkers and led by an adjuvant.

CONCLUSION

Our investigations predicted epitopes and the reported molecules that may have the potential to inhibit the SARS-CoV-2 virus. These findings can be a step towards the development of a peptide-based vaccine or natural compound drug target against SARS-CoV-2.

The first Conus genome assembly reveals a primary genetic central dogma of conopeptides in C. betulinus

Although there are various Conus species with publicly available transcriptome and proteome data, no genome assembly has been reported yet. Here, using Chinese tubular cone snail (C. betulinus) as a representative, we sequenced and assembled the first Conus genome with original identification of 133 genome-widely distributed conopeptide genes. After integration of our genomics, transcriptomics, and peptidomics data in the same species, we established a primary genetic central dogma of diverse conopeptides, assuming a rough number ratio of ~1:1:1:10s for the total genes: transcripts: proteins: post-translationally modified peptides. This ratio may be special for this worm-hunting Conus species, due to the high diversity of various Conus genomes and the big number ranges of conopeptide genes, transcripts, and peptides in previous reports of diverse Conus species. Only a fraction (45.9%) of the identified conotopeptide genes from our achieved genome assembly are transcribed with transcriptomic evidence, and few genes individually correspond to multiple transcripts possibly due to intraspecies or mutation-based variances. Variable peptide processing at the proteomic level, generating a big diversity of venom conopeptides with alternative cleavage sites, post-translational modifications, and N-/C-terminal truncations, may explain how the 133 genes and ~123 transcripts can generate thousands of conopeptides in the venom of individual C. betulinus. We also predicted many conopeptides with high stereostructural similarities to the putative analgesic ω-MVIIA, addiction therapy AuIB and insecticide ImI, suggesting that our current genome assembly for C. betulinus is a valuable genetic resource for high-throughput prediction and development of potential pharmaceuticals.

Thiazole-Based Thiosemicarbazones: Synthesis, Cytotoxicity Evaluation and Molecular Docking Study

INTRODUCTION

Hybrid drug design has developed as a prime method for the development of novel anticancer therapies that can theoretically solve much of the pharmacokinetic disadvantages of traditional anticancer drugs. Thus a number of studies have indicated that thiazole-thiophene hybrids and their bis derivatives have important anticancer activity. Mammalian Rab7b protein is a member of the Rab GTPase protein family that controls the trafficking from endosomes to the TGN. Alteration in the Rab7b expression is implicated in differentiation of malignant cells, causing cancer.

METHODS

1-(4-Methyl-2-(2-(1-(thiophen-2-yl) ethylidene) hydrazinyl) thiazol-5-yl) ethanone was used as building block for synthesis of novel series of 5-(1-(2-(thiazol-2-yl) hydrazono) ethyl) thiazole derivatives. The bioactivities of the synthesized compounds were evaluated with respect to their antitumor activities against MCF-7 tumor cells using MTT assay. Computer-aided docking protocol was performed to study the possible molecular interactions between the newly synthetic thiazole compounds and the active binding site of the target protein Rab7b. Moreover, the in silico prediction of adsorption, distribution, metabolism, excretion (ADME) and toxicity (T) properties of synthesized compounds were carried out using admetSAR tool.

RESULTS

The results obtained showed that derivatives 9 and 11b have promising activity (IC50 = 14.6 ± 0.8 and 28.3 ± 1.5 µM, respectively) compared to Cisplatin (IC50 = 13.6 ± 0.9 µM). The molecular docking analysis reveals that the synthesized compounds are predicted to be fit into the binding site of the target Rab7b. In summary, the synthetic thiazole compounds 1-17 could be used as potent inhibitors as anticancer drugs.

CONCLUSION

Promising anticancer activity of compounds 9 and 11 compared with cisplatin reference drug suggests that these ligands may contribute as lead compounds in search of new anticancer agents to combat chemo-resistance.

Genome-Wide Identification and Characterization of Wheat 14-3-3 Genes Unravels the Role of TaGRF6-A in Salt Stress Tolerance by Binding MYB Transcription Factor

14-3-3 proteins are a large multigenic family of general regulatory factors (GRF) ubiquitously found in eukaryotes and play vital roles in the regulation of plant growth, development, and response to stress stimuli. However, so far, no comprehensive investigation has been performed in the hexaploid wheat. In the present study, A total of 17 potential 14-3-3 gene family members were identified from the Chinese Spring whole-genome sequencing database. The phylogenetic comparison with six 14-3-3 families revealed that the majority of wheat 14-3-3 genes might have evolved as an independent branch and grouped into ε and non-ε group using the phylogenetic comparison. Analysis of gene structure and motif indicated that 14-3-3 protein family members have relatively conserved exon/intron arrangement and motif composition. Physical mapping showed that wheat 14-3-3 genes are mainly distributed on chromosomes 2, 3, 4, and 7. Moreover, most 14-3-3 members in wheat exhibited significantly down-regulated expression in response to alkaline stress. VIGS assay and protein-protein interaction analysis further confirmed that TaGRF6-A positively regulated slat stress tolerance by interacting with a MYB transcription factor, TaMYB64. Taken together, our findings provide fundamental information on the involvement of the wheat 14-3-3 family in salt stress and further investigating their molecular mechanism.

Characterization and Function of a Novel Welan Gum Lyase From Marine Sphingomonas sp. WG

Welan gum, a kind of microbial exopolysaccharides, produced by the genus Sphingomonas, have great potential for application in many fields, such as the food industry, cement production, and enhanced oil recovery. But there are still challenges to reduce the cost, enhance the production and the quality. Herein, the bioinformatics analysis of WelR gene was preformed, and the characterization and function of WelR, welan gum lyase, from Sphingomonas sp. WG were investigated for the first time. The results indicated that 382nd (Asn), 383rd (Met), 494th (Asn), and 568th (Glu) were the key amino acid residues, and C-terminal amino acids were essential to keeping the stability of WelR. The optimal temperature and pH of the enzymatic activity were found to be 25°C and 7.4, respectively. And WelR was good low temperature resistance and alkali resistant. K+, Mg2+, Ca2+, Mn2+, and EDTA increased WelR activities, in contrast to Zn2+. Coupled with the change in glucose concentration and growth profile, the qRT-PCR results indicated that WelR may degrade welan gum existing in the culture to maintain bacterial metabolism when glucose was depleted. This work will lay a theoretical foundation to establish new strategies for the regulation of welan gum biosynthesis.

Designing a next generation multi-epitope based peptide vaccine candidate against SARS-CoV-2 using computational approaches

COVID-19 caused by SARS-CoV-2 was declared a global pandemic by WHO (World Health Organization) in March, 2020. Within 6 months, nearly 750,000 deaths are claimed by COVID-19 across the globe. This called for immediate social, scientific, technological, public and community interventions. Considering the severity of infection and the associated mortalities, global efforts are underway to develop preventive measures against SARS-CoV-2. Among the SARS-CoV-2 target proteins, Spike (S) glycoprotein (a.k.a S Protein) is the most studied target known to trigger strong host immune response. A detailed analysis of S protein-based epitopes enabled us to design a novel B-cell-derived T-cell Multi-epitope-based peptide (MEBP) vaccine candidate. This involved a systematic and comprehensive computational protocol consisting of prediction of dual-purpose epitopes and designing an MEBP vaccine construct. This was followed by 3D structure validation, MEBP complex interaction studies, in silico cloning and vaccine dose-based immune response simulation to evaluate the immunogenic potency of the vaccine construct. The dual-purpose epitope prediction protocol was designed such that the same epitope elicits both humoral and cellular immune response unlike the earlier designs. Further, the epitopes predicted were screened against stringent criteria to ensure selection of a potent candidate with maximum antigen coverage and best immune response. The vaccine dose-based immune response simulation studies revealed a rapid antigen clearance through antibody generation and elevated levels of cell-mediated immunity during repeated exposure of the vaccine. The favourable results of the analysis strongly indicate that the vaccine construct is indeed a potent vaccine candidate and ready to proceed to the next steps of experimental validation and efficacy studies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-020-02574-x.

Functional analysis of a novel cryptochrome gene (GbCRY1) from Ginkgo biloba

Cryptochrome (CRY) is a blue light receptor that is widely distributed in animals, plants, and microorganisms. CRY as a coding gene of cryptochrome that regulates the organism gene expression and plays an important role in organism growth and development. In this study, we identified four photolyase/cryptochrome (PHR/CRY) members from the genome of Ginkgo biloba. Phylogenetic tree analysis showed that the Ginkgo PHR/CRY family members were closely related to Arabidopsis thaliana and Solanum lycopersicum. We isolated a cryptochrome gene, GbCRY1, from G. biloba and analyzed its structure and function. GbCRY1 shared high similarity with AtCRY1 from A. thaliana. GbCRY1 expression level was higher in stems and leaves and lower in roots, male strobili, female strobili. GbCRY1 expression level fluctuated periodically within 24 h, gradually increased in the dark, and decreased under blue light. The newly germinated ginkgo seedlings were cultured under dark, white light, and blue light conditions. The blue light normally induced photomorphogenesis of ginkgo seedlings, which included hypocotyl elongation inhibition, leaf expansion inhibition, and chlorophyll formation. Treating dark-adapted ginkgo leaves with blue light could induce stomatal opening. At the same time, blue light reduced the expression level of GbCRY1 in the process of inducing photomorphogenesis and stoma opening. Our results provide evidence that GbCRY1 expression is affected by space, circadian cycle and light, and also proves that GbCRY1 is related to ginkgo circadian clock, photomorphogenesis and stoma opening process.

Genome-wide analysis of haloacid dehalogenase genes reveals their function in phosphate starvation responses in rice

The HAD superfamily is named after the halogenated acid dehalogenase found in bacteria, which hydrolyses a diverse range of organic phosphate substrates. Although certain studies have shown the involvement of HAD genes in Pi starvation responses, systematic classification and bioinformatics analysis of the HAD superfamily in plants is lacking. In this study, 41 and 40 HAD genes were identified by genomic searching in rice and Arabidopsis, respectively. According to sequence similarity, these proteins are divided into three major groups and seven subgroups. Conserved motif analysis indicates that the majority of the identified HAD proteins contain phosphatase domains. A further structural analysis showed that HAD proteins have four conserved motifs and specified cap domains. Fewer HAD genes show collinearity relationships in both rice and Arabidopsis, which is consistent with the large variations in the HAD genes. Among the 41 HAD genes of rice, the promoters of 28 genes contain Pi-responsive cis-elements. Mining of transcriptome data and qRT-PCR results showed that at least the expression of 17 HAD genes was induced by Pi starvation in shoots or roots. These HAD proteins are predicted to be involved in intracellular or extracellular Po recycling under Pi stress conditions in plants.

Human body-fluid proteome: quantitative profiling and computational prediction

Empowered by the advancement of high-throughput bio technologies, recent research on body-fluid proteomes has led to the discoveries of numerous novel disease biomarkers and therapeutic drugs. In the meantime, a tremendous progress in disclosing the body-fluid proteomes was made, resulting in a collection of over 15 000 different proteins detected in major human body fluids. However, common challenges remain with current proteomics technologies about how to effectively handle the large variety of protein modifications in those fluids. To this end, computational effort utilizing statistical and machine-learning approaches has shown early successes in identifying biomarker proteins in specific human diseases. In this article, we first summarized the experimental progresses using a combination of conventional and high-throughput technologies, along with the major discoveries, and focused on current research status of 16 types of body-fluid proteins. Next, the emerging computational work on protein prediction based on support vector machine, ranking algorithm, and protein-protein interaction network were also surveyed, followed by algorithm and application discussion. At last, we discuss additional critical concerns about these topics and close the review by providing future perspectives especially toward the realization of clinical disease biomarker discovery.

Characterization of the SARS-CoV-2 S Protein: Biophysical, Biochemical, Structural, and Antigenic Analysis

Coronavirus disease 2019 (COVID-19) is a global health crisis caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and there is a critical need to produce large quantities of high-quality SARS-CoV-2 Spike (S) protein for use in both clinical and basic science settings. To address this need, we have evaluated the expression and purification of two previously reported S protein constructs in Expi293F and ExpiCHO-S cells, two different cell lines selected for increased protein expression. We show that ExpiCHO-S cells produce enhanced yields of both SARS-CoV-2 S proteins. Biochemical, biophysical, and structural (cryo-EM) characterizations of the SARS-CoV-2 S proteins produced in both cell lines demonstrate that the reported purification strategy yields high-quality S protein (nonaggregated, uniform material with appropriate biochemical and biophysical properties), and analysis of 20 deposited S protein cryo-EM structures reveals conformation plasticity in the region composed of amino acids 614-642 and 828-854. Importantly, we show that multiple preparations of these two recombinant S proteins from either cell line exhibit identical behavior in two different serology assays. We also evaluate the specificity of S protein-mediated host cell binding by examining interactions with proposed binding partners in the human secretome and report no novel binding partners and notably fail to validate the Spike:CD147 interaction. In addition, the antigenicity of these proteins is demonstrated by standard ELISAs and in a flexible protein microarray format. Collectively, we establish an array of metrics for ensuring the production of high-quality S protein to support clinical, biological, biochemical, structural, and mechanistic studies to combat the global pandemic caused by SARS-CoV-2.

A novel type of colistin resistance genes selected from random sequence space

Antibiotic resistance is a rapidly increasing medical problem that severely limits the success of antibiotic treatments, and the identification of resistance determinants is key for surveillance and control of resistance dissemination. Horizontal transfer is the dominant mechanism for spread of resistance genes between bacteria but little is known about the original emergence of resistance genes. Here, we examined experimentally if random sequences can generate novel antibiotic resistance determinants de novo. By utilizing highly diverse expression libraries encoding random sequences to select for open reading frames that confer resistance to the last-resort antibiotic colistin in Escherichia coli, six de novocolistin resistance conferring peptides (Dcr) were identified. The peptides act via direct interactions with the sensor kinase PmrB (also termed BasS in E. coli), causing an activation of the PmrAB two-component system (TCS), modification of the lipid A domain of lipopolysaccharide and subsequent colistin resistance. This kinase-activation was extended to other TCS by generation of chimeric sensor kinases. Our results demonstrate that peptides with novel activities mediated via specific peptide-protein interactions in the transmembrane domain of a sensory transducer can be selected de novo, suggesting that the origination of such peptides from non-coding regions is conceivable. In addition, we identified a novel class of resistance determinants for a key antibiotic that is used as a last resort treatment for several significant pathogens. The high-level resistance provided at low expression levels, absence of significant growth defects and the functionality of Dcr peptides across different genera suggest that this class of peptides could potentially evolve as bona fide resistance determinants in natura.

We expressed over 100 million randomly generated DNA sequences in Escherichia coli and selected 6 variants that encode peptides that provide resistance to the last-resort antibiotic colistin. We show that the selected peptides are auxiliary activators of the two-component system PmrAB, and that resistance is mediated via modifications of the cell envelope causing decreased antibiotic uptake. This is the first example where random expression libraries have been employed to select for peptides that perform an activating function by direct peptide-protein interactions in vivo, adding support to the idea that non-coding DNA can serve as a substrate for de novo gene evolution. Additionally, the described peptides expand the narrow list of colistin resistance genes and further analyses of clinical isolates will be necessary to determine if similar resistance determinants have evolved in natura.

Isolating SARS-CoV-2 Strains From Countries in the Same Meridian: Genome Evolutionary Analysis

BACKGROUND

COVID-19, caused by the novel SARS-CoV-2, is considered the most threatening respiratory infection in the world, with over 40 million people infected and over 0.934 million related deaths reported worldwide. It is speculated that epidemiological and clinical features of COVID-19 may differ across countries or continents. Genomic comparison of 48,635 SARS-CoV-2 genomes has shown that the average number of mutations per sample was 7.23, and most SARS-CoV-2 strains belong to one of 3 clades characterized by geographic and genomic specificity: Europe, Asia, and North America.

OBJECTIVE

The aim of this study was to compare the genomes of SARS-CoV-2 strains isolated from Italy, Sweden, and Congo, that is, 3 different countries in the same meridian (longitude) but with different climate conditions, and from Brazil (as an outgroup country), to analyze similarities or differences in patterns of possible evolutionary pressure signatures in their genomes.

METHODS

We obtained data from the Global Initiative on Sharing All Influenza Data repository by sampling all genomes available on that date. Using HyPhy, we achieved the recombination analysis by genetic algorithm recombination detection method, trimming, removal of the stop codons, and phylogenetic tree and mixed effects model of evolution analyses. We also performed secondary structure prediction analysis for both sequences (mutated and wild-type) and "disorder" and "transmembrane" analyses of the protein. We analyzed both protein structures with an ab initio approach to predict their ontologies and 3D structures.

RESULTS

Evolutionary analysis revealed that codon 9628 is under episodic selective pressure for all SARS-CoV-2 strains isolated from the 4 countries, suggesting it is a key site for virus evolution. Codon 9628 encodes the P0DTD3 (Y14_SARS2) uncharacterized protein 14. Further investigation showed that the codon mutation was responsible for helical modification in the secondary structure. The codon was positioned in the more ordered region of the gene (41-59) and near to the area acting as the transmembrane (54-67), suggesting its involvement in the attachment phase of the virus. The predicted protein structures of both wild-type and mutated P0DTD3 confirmed the importance of the codon to define the protein structure. Moreover, ontological analysis of the protein emphasized that the mutation enhances the binding probability.

CONCLUSIONS

Our results suggest that RNA secondary structure may be affected and, consequently, the protein product changes T (threonine) to G (glycine) in position 50 of the protein. This position is located close to the predicted transmembrane region. Mutation analysis revealed that the change from G (glycine) to D (aspartic acid) may confer a new function to the protein-binding activity, which in turn may be responsible for attaching the virus to human eukaryotic cells. These findings can help design in vitro experiments and possibly facilitate a vaccine design and successful antiviral strategies.

FXR1 splicing is important for muscle development and biomolecular condensates in muscle cells

Fragile-X mental retardation autosomal homologue-1 (FXR1) is a muscle-enriched RNA-binding protein. FXR1 depletion is perinatally lethal in mice, Xenopus, and zebrafish; however, the mechanisms driving these phenotypes remain unclear. The FXR1 gene undergoes alternative splicing, producing multiple protein isoforms and mis-splicing has been implicated in disease. Furthermore, mutations that cause frameshifts in muscle-specific isoforms result in congenital multi-minicore myopathy. We observed that FXR1 alternative splicing is pronounced in the serine- and arginine-rich intrinsically disordered domain; these domains are known to promote biomolecular condensation. Here, we show that tissue-specific splicing of fxr1 is required for Xenopus development and alters the disordered domain of FXR1. FXR1 isoforms vary in the formation of RNA-dependent biomolecular condensates in cells and in vitro. This work shows that regulation of tissue-specific splicing can influence FXR1 condensates in muscle development and how mis-splicing promotes disease.

Fermented Soy-Derived Bioactive Peptides Selected by a Molecular Docking Approach Show Antioxidant Properties Involving the Keap1/Nrf2 Pathway

Bioactive peptides are a group of molecules with health beneficial properties, deriving from food matrices. They are protein fragments consisting of 2–20 amino acids that can be released by microbial fermentation, food processing and gastrointestinal digestion. Once hydrolyzed from their native proteins, they can have different functions including antioxidant activity, which is important for cell protection by oxidant agents. In this work, fermented soy products were digested in vitro in order to improve the release of bioactive peptides. These were extracted, purified and analyzed in vitro and in a cellular model to assess their antioxidant activity. Peptide sequences were identified by LC-MS/MS analysis and a molecular docking approach was used to predict their ability to interact with Keap1, one of the key proteins of the Keap1/Nrf2 pathway, the major system involved in redox regulation. Peptides showing a high score of interaction were selected and tested for their antioxidant properties in a cellular environment using the Caco-2 cell line and examined for their capability to defend cells against oxidative stress. Our results indicate that several of the selected peptides were indeed able to activate the Keap1/Nrf2 pathway with the consequent overexpression of antioxidant and phase II enzymes.

Uncovering Roles of Streptococcus gordonii SrtA-Processed Proteins in the Biofilm Lifestyle

Streptococcus gordonii is a commensal oral organism. Harmless in the oral cavity, S. gordonii is an opportunistic pathogen. S. gordonii adheres to body surfaces using surface adhesive proteins (adhesins), which are critical to subsequent formation of biofilm communities. As in most Gram-positive bacteria, S. gordonii surface proteins containing the C-terminal LPXTG motif cleavage sequence are processed by sortase A (SrtA) to become covalently attached to the cell wall. To characterize the functional diversity and redundancy in the family of SrtA-processed proteins, an S. gordonii DL1 markerless deletion mutant library was constructed of each of the 26 putative SrtA-processed proteins. Each library member was evaluated for growth in rich medium, biofilm formation on plastic, saliva and salivary fractions, cell surface hydrophobicity (CSH), hemagglutination, and integration into an ex vivo plaque biofilm community. Library members were compared to the non-SrtA-processed adhesins AbpA and AbpB. While no major growth differences in rich medium were observed, many S. gordonii LPXTG/A proteins impacted biofilm formation on one or more of the substrates. Several mutants showed significant differences in hemagglutination, hydrophobicity, or fitness in the ex vivo plaque model. From the identification of redundant and unique functions in these in vitro and ex vivo systems, functional stratification among the LPXTG/A proteins is apparent.IMPORTANCE S. gordonii interactions with its environment depend on the complement of cell wall proteins. A subset of these cell wall proteins requires processing by the enzyme sortase A (SrtA). The identification of SrtA-processed proteins and their functional characterization will help the community to better understand how S. gordonii engages with its surroundings, including other microbes, integrates into the plaque community, adheres to the tooth surface, and hematogenously disseminates to cause blood-borne infections. This study identified 26 putative SrtA-processed proteins through creation of a markerless deletion mutant library. The library was subject to functional screens that were chosen to better understand key aspects of S. gordonii physiology and pathogenesis.

A domain-based vaccine construct against SARS-CoV-2, the causative agent of COVID-19 pandemic: development of self-amplifying mRNA and peptide vaccines

Introduction: Coronavirus disease 2019 (COVID-19) is undoubtedly the most challenging pandemic in the current century with more than 293,241 deaths worldwide since its emergence in late 2019 (updated May 13, 2020). COVID-19 is caused by a novel emerged coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Today, the world needs crucially to develop a prophylactic vaccine scheme for such emerged and emerging infectious pathogens. Methods: In this study, we have targeted spike (S) glycoprotein, as an important surface antigen to identify its B- and T-cell immunodominant regions. We have conducted a multi-method B-cell epitope (BCE) prediction approach using different predictor algorithms to discover the most potential BCEs. Besides, we sought among a pool of MHC class I and II-associated peptide binders provided by the IEDB server through the strict cut-off values. To design a broad-coverage vaccine, we carried out a population coverage analysis for a set of candidate T-cell epitopes and based on the HLA allele frequency in the top most-affected countries by COVID-19 (update 02 April 2020). Results: The final determined B- and T-cell epitopes were mapped on the S glycoprotein sequence, and three potential hub regions covering the largest number of overlapping epitopes were identified for the vaccine designing (I531-N711; T717-C877; and V883-E973). Here, we have designed two domain-based constructs to be produced and delivered through the recombinant protein- and gene-based approaches, including (i) an adjuvanted domain-based protein vaccine construct (DPVC), and (ii) a self-amplifying mRNA vaccine (SAMV) construct. The safety, stability, and immunogenicity of the DPVC were validated using the integrated sequential (i.e. allergenicity, autoimmunity, and physicochemical features) and structural (i.e. molecular docking between the vaccine and human Toll-like receptors (TLRs) 4 and 5) analysis. The stability of the docked complexes was evaluated using the molecular dynamics (MD) simulations. Conclusion: These rigorous in silico validations supported the potential of the DPVC and SAMV to promote both innate and specific immune responses in preclinical studies.

Electrochemistry as a surrogate for protein phosphorylation: voltage-controlled assembly of reflectin A1

Phosphorylation is among the most widely distributed mechanisms regulating the tunable structure and function of proteins in response to neuronal, hormonal and environmental signals. We demonstrate here that the low-voltage electrochemical reduction of histidine residues in reflectin A1, a protein that mediates the neuronal fine-tuning of colour reflected from skin cells for camouflage and communication in squids, acts as an in vitro surrogate for phosphorylation in vivo, driving the assembly previously shown to regulate its function. Using micro-drop voltammetry and a newly designed electrochemical cell integrated with an instrument measuring dynamic light scattering, we demonstrate selective reduction of the imidazolium side chains of histidine in monomers, oligopeptides and this complex protein in solution. The formal reduction potential of imidazolium proves readily distinguishable from those of hydronium and primary amines, allowing unequivocal confirmation of the direct and energetically selective deprotonation of histidine in the protein. The resulting 'electro-assembly' provides a new approach to probe, understand, and control the mechanisms that dynamically tune protein structure and function in normal physiology and disease. With its abilities to serve as a surrogate for phosphorylation and other mechanisms of charge neutralization, and to potentially isolate early intermediates in protein assembly, this method may be useful for analysing never-before-seen early intermediates in the phosphorylation-driven assembly of other proteins in normal physiology and disease.

IiWRKY34 positively regulates yield, lignan biosynthesis and stress tolerance in Isatis indigotica

Yield potential, pharmaceutical compounds production and stress tolerance capacity are 3 classes of traits that determine the quality of medicinal plants. The autotetraploid Isatis indigotica has greater yield, higher bioactive lignan accumulation and enhanced stress tolerance compared with its diploid progenitor. Here we show that the transcription factor IiWRKY34, with higher expression levels in tetraploid than in diploid I. indigotica, has large pleiotropic effects on an array of traits, including biomass growth rates, lignan biosynthesis, as well as salt and drought stress tolerance. Integrated analysis of transcriptome and metabolome profiling demonstrated that IiWRKY34 expression had far-reaching consequences on both primary and secondary metabolism, reprograming carbon flux towards phenylpropanoids, such as lignans and flavonoids. Transcript–metabolite correlation analysis was applied to construct the regulatory network of IiWRKY34 for lignan biosynthesis. One candidate target Ii4CL3, a key rate-limiting enzyme of lignan biosynthesis as indicated in our previous study, has been demonstrated to indeed be activated by IiWRKY34. Collectively, the results indicate that the differentially expressed IiWRKY34 has contributed significantly to the polyploidy vigor of I. indigotica, and manipulation of this gene will facilitate comprehensive improvements of I. indigotica herb.

Genome-Wide Identification and Expression Profiling Analysis of the Trihelix Gene Family Under Abiotic Stresses in Medicago truncatula

The trihelix transcription factor (GT) family is widely involved in regulating plant growth and development, and most importantly, responding to various abiotic stresses. Our study first reported the genome-wide identification and analysis of GT family genes in Medicago truncatula. Overall, 38 trihelix genes were identified in the M. truncatula genome and were classified into five subfamilies (GT-1, GT-2, SH4, GTγ and SIP1). We systematically analyzed the phylogenetic relationship, chromosomal distribution, tandem and segmental duplication events, gene structures and conserved motifs of MtGTs. Syntenic analysis revealed that trihelix family genes in M. truncatula had the most collinearity relationship with those in soybean followed by alfalfa, but very little collinearity with those in the maize and rice. Additionally, tissue-specific expression analysis of trihelix family genes suggested that they played various roles in the growth and development of specific tissues in M. truncatula. Moreover, the expression of some MtGT genes, such as MtGT19, MtGT20, MtGT22, and MtGT33, was dramatically induced by drought, salt, and ABA treatments, illustrating their vital roles in response to abiotic stresses. These findings are helpful for improving the comprehensive understanding of trihelix family; additionally, the study provides candidate genes for achieving the genetic improvement of stress resistance in legumes.

Transcriptome-wide identification of MAPKKK genes in bermudagrass (Cynodon dactylon L.) and their potential roles in low temperature stress responses

As upstream components of MAPK cascades, mitogen-activated protein kinase kinase kinases (MAPKKKs) act as adaptors linking upstream signaling steps to the core MAPK cascades. MAPK cascades are universal modules of signal transduction in eukaryotic organisms and play crucial roles in plant development processes and in responses to biotic and abiotic stress and signal transduction. Members of the MAPKKK gene family have been identified in several plants,however, MAPKKKs have not been systematically studied in bermudagrass (Cynodon dactylon L.). In this study, 55 potential CdMAPKKKs were produced from bermudagrass transcriptome data, of which 13 belonged to the MEKK, 38 to the Raf, and 4 to the ZIK subfamily. Multiple alignment and conserved motif analysis of CdMAPKKKs supported the evolutionary relationships inferred from phylogenetic analyses. Moreover, the distribution pattern in Poaceae species indicated that members of the MAPKKK family were conserved among almost all diploid species, and species-specific polyploidy or higher duplication ratios resulted in an expansion of the MAPKKK family. In addition, 714 co-functional links which were significantly enriched in signal transduction, responses to temperature stimuli, and other important biological processes of 55 CdMAPKKKs were identified using co-functional gene networks analysis; 30 and 19 co-functional genes involved in response to cold or heat stress, respectively, were also identified. Results of promoter analyses, and interaction network investigation of all CdMAPKKKs based on the rice homologs suggested that CdMAPKKKs are commonly associated with regulation of numerous biological processes. Furthermore, 12 and 13 CdMAPKKKs were significantly up- and downregulated, respectively, in response to low temperature stress; among them, six CdMAPKKKs were significantly induced by low temperature stress, at least at one point in time. This is the first study to conduct identification and functional analysis of the MAPKKK gene family in bermudagrass, and our results provide a foundation for further research on the functions of CdMAPKKKs in response to low temperature stress.

Genome-wide identification, and phylogenetic and expression profiling analyses, of XTH gene families in Brassica rapa L. and Brassica oleracea L

BACKGROUND

Xyloglucan endotransglucosylase/hydrolase genes (XTHs) are a multigene family and play key roles in regulating cell wall extensibility in plant growth and development. Brassica rapa and Brassica oleracea contain XTHs, but detailed identification and characterization of the XTH family in these species, and analysis of their tissue expression profiles, have not previously been carried out.

RESULTS

In this study, 53 and 38 XTH genes were identified in B. rapa and B. oleracea respectively, which contained some novel members not observed in previous studies. All XTHs of B. rapa, B. oleracea and Arabidopsis thaliana could be classified into three groups, Group I/II, III and the Early diverging group, based on phylogenetic relationships. Gene structures and motif patterns were similar within each group. All XTHs in this study contained two characteristic conserved domains (Glyco_hydro and XET_C). XTHs are located mainly in the cell wall but some are also located in the cytoplasm. Analyses of the mechanisms of gene family expansion revealed that whole-genome triplication (WGT) events and tandem duplication (TD) may have been the major mechanisms accounting for the expansion of the XTH gene family. Interestingly, TD genes all belonged to Group I/II, suggesting that TD was the main reason for the largest number of genes being in these groups. B. oleracea had lost more of the XTH genes, the conserved domain XET_C and the conserved active-site motif EXDXE compared with B. rapa, consistent with asymmetrical evolution between the two Brassica genomes. A majority of XTH genes exhibited different tissue-specific expression patterns based on RNA-seq data analyses. Moreover, there was differential expression of duplicated XTH genes in the two species, indicating that their functional differentiation occurred after B. rapa and B. oleracea diverged from a common ancestor.

CONCLUSIONS

We carried out the first systematic analysis of XTH gene families in B. rapa and B. oleracea. The results of this investigation can be used for reference in further studies on the functions of XTH genes and the evolution of this multigene family.

Translating the Concept of Bispecific Antibodies to Engineering Heterodimeric Phosphotriesterases with Broad Organophosphate Substrate Recognition

We have adopted the concept of bispecific antibodies, which can simultaneously block or cross-link two different biomolecular targets, to create bispecific enzymes by exploiting the homodimeric quaternary structure of bacterial phosphotriesterases (PTEs). The PTEs from Brevundimonas diminuta and Agrobacterium radiobacter, whose engineered variants can efficiently hydrolyze organophosphorus (OP) nerve agents and pesticides, respectively, have attracted considerable interest for the treatment of the corresponding intoxications. OP nerve agents and pesticides still pose a severe toxicological threat in military conflicts, including acts of terrorism, as well as in agriculture, leading to >100000 deaths per year. In principle, engineered conventional homodimeric PTEs may provoke hydrolytic inactivation of individual OPs in vivo, and their application as catalytic bioscavengers via administration into the bloodstream has been proposed. However, their narrow substrate specificity would necessitate therapeutic application of a set or mixture of different enzymes, which complicates biopharmaceutical development. We succeeded in combining subunits from both enzymes and to stabilize their heterodimerization by rationally designing electrostatic steering mutations, thus breaking the natural C2 symmetry. The resulting bispecific enzyme from two PTEs with different bacterial origin exhibits an ultrabroad OP substrate profile and allows the efficient detoxification of both nerve agents and pesticides. Our approach of combining two active sites with distinct substrate specificities within one artificial dimeric biocatalyst-retaining the size and general properties of the original enzyme without utilizing protein mixtures or much larger fusion proteins-not only should facilitate biological drug development but also may be applicable to oligomeric enzymes with other catalytic activities.

Designing a novel mRNA vaccine against SARS-CoV-2: An immunoinformatics approach

SARS-CoV-2 is the deadly virus behind COVID-19, the disease that went on to ravage the world and caused the biggest pandemic 21st century has witnessed so far. On the face of ongoing death and destruction, the urgent need for the discovery of a vaccine against the virus is paramount. This study resorted to the emerging discipline of immunoinformatics in order to design a multi-epitope mRNA vaccine against the spike glycoprotein of SARS-CoV-2. Various immunoinformatics tools were utilized to predict T and B lymphocyte epitopes. The epitopes were channeled through a filtering pipeline comprised of antigenicity, toxicity, allergenicity, and cytokine inducibility evaluation with the goal of selecting epitopes capable of generating both T and B cell-mediated immune responses. Molecular docking simulation between the epitopes and their corresponding MHC molecules was carried out. 13 epitopes, a highly immunogenic adjuvant, elements for proper sub-cellular trafficking, a secretion booster, and appropriate linkers were combined for constructing the vaccine. The vaccine was found to be antigenic, almost neutral at physiological pH, non-toxic, non-allergenic, capable of generating a robust immune response and had a decent worldwide population coverage. Based on these parameters, this design can be considered a promising choice for a vaccine against SARS-CoV-2.

Genome-wide analysis of HSP90 gene family in the Mediterranean olive (Olea europaea subsp. europaea) provides insight into structural patterns, evolution and functional diversity

Plants regularly experience multiple abiotic and biotic pressures affecting their normal development. The 90-kDa heat shock protein (HSP90) plays a dynamic role in countering abiotic and biotic stresses via a plethora of functional mechanisms. The HSP90 has been investigated in many plant species. However, there is little information available about this gene family in the cultivated Mediterranean olive tree, Olea europaea subsp. europaea var. europaea. In the current study, we systematically performed genome-wide identification and characterization of the HSP90 gene family in O. europaea var. europaea (OeHSP90s). Twelve regular OeHSP90s were identified, which were phylogenetically grouped into two major clusters and four sub-clusters, showing five paralogous gene pairs evolving under purifying selection. All of the 12 proteins contained a Histidine kinase-like ATPase (HATPase_c) domain, justifying the role played by HSP90 proteins in ATP binding and hydrolysis. The predicted 3D structure of OeHSP90 proteins provided information to understand their functions at the biochemical level. Consistent with their phylogenetic relationships, OeHSP90 members were predicted to be localized in different cellular compartments, suggesting their involvement in various subcellular processes. In consonance with their spatial organization, olive HSP90 family members were found to share similar motif arrangements and similar number of exons. We found that OeHSP90 promoters contained various cis-acting elements associated with light responsiveness, hormone signaling pathways and reaction to various stress conditions. In addition, expression sequence tags (ESTs) analysis offered a view of OeHSP90 tissue- and developmental stage specific pattern of expression. Proteins interacting with OeHSP90s were predicted and their potential roles were discussed. Overall, our results offer premises for further investigation of the implication of HSP90 genes in the physiological processes of the olive and its adaptation to stresses.

Solution NMR structure of Se0862, a highly conserved cyanobacterial protein involved in biofilm formation

Biofilms are accumulations of microorganisms embedded in extracellular matrices that protect against external factors and stressful environments. Cyanobacterial biofilms are ubiquitous and have potential for treatment of wastewater and sustainable production of biofuels. But the underlying mechanisms regulating cyanobacterial biofilm formation are unclear. Here, we report the solution NMR structure of a protein, Se0862, conserved across diverse cyanobacterial species and involved in regulation of biofilm formation in the cyanobacterium Synechococcus elongatus PCC 7942. Se0862 is a class α+β protein with ααββββαα topology and roll architecture, consisting of a four-stranded β-sheet that is flanked by four α-helices on one side. Conserved surface residues constitute a hydrophobic pocket and charged regions that are likely also present in Se0862 orthologs.

Structural Insight on Functional Regulation of Human MINERVA Protein

MINERVA (melanoma invasion by ERK), also known as FAM129B, is a member of the FAM129 protein family, which is only present in vertebrates. MINERVA is involved in key signaling pathways regulating cell survival, proliferation and apoptosis and found upregulated in many types of cancer promoting invasion. However, the exact function of the protein remains elusive. X-ray crystallographic methods were implemented to determine the crystal structure of MINERVA^ΔC, lacking C-terminal flexible region. Trypsin digestion was required before crystallization to obtain diffraction-quality crystals. While the N-terminal pleckstrin homology (PH) domain exhibits the typical fold of PH domains, lipid binding assay indicates specific affinity towards phosphatidic acid and inositol 3-phosphate. A helix-rich domain that constitutes the rest of the molecule demonstrates a novel L-shaped fold that encompasses the PH domain. The overall structure of MINERVA^ΔC with binding assays and cell-based experiments suggest plasma membrane association of MINERVA and its function seem to be tightly regulated by various motifs within the C-terminal flexible region. Elucidation of MINERVA^ΔC structure presents a novel fold for an α-helix bundle domain that would provide a binding platform for interacting partners.

Structural Insights into β-arrestin/CB1 Receptor Interaction: NMR and CD Studies on Model Peptides

Activation of the cannabinoid CB1 receptor induces different cellular signaling cascades through coupling to different effector proteins (G-proteins and β-arrestins), triggering numerous therapeutic effects. Conformational changes and rearrangements at the intracellular domain of this GPCR receptor that accompany ligand binding dictate the signaling pathways. The GPCR-binding interface for G proteins has been extensively studied, whereas β-arrestin/GPCR complexes are still poorly understood. To gain knowledge in this direction, we designed peptides that mimic the motifs involved in the putative interacting region: β-arrestin1 finger loop and the transmembrane helix 7-helix 8 (TMH7-H8) elbow located at the intracellular side of the CB1 receptor. According to circular dichroism and NMR data, these peptides form a native-like, helical conformation and interact with each other in aqueous solution, in the presence of trifluoroethanol, and using zwitterionic detergent micelles as membrane mimics. These results increase our understanding of the binding mode of β-arrestin and CB1 receptor and validate minimalist approaches to structurally comprehend complex protein systems.

Adding Size Exclusion Chromatography (SEC) and Light Scattering (LS) Devices to Obtain High-Quality Small Angle X-Ray Scattering (SAXS) Data

We describe the updated size-exclusion chromatography small angle X-ray scattering (SEC-SAXS) set-up used at the P12 bioSAXS beam line of the European Molecular Biology Laboratory (EMBL) at the PETRAIII synchrotron, DESY Hamburg (Germany). The addition of size exclusion chromatography (SEC) directly on-line to the SAXS capillary has become a well-established approach to reduce the effects of the sample heterogeneity on the SAXS measurements. The additional use of multi-angle laser light scattering (MALLS), UV absorption spectroscopy, refractive index (RI), and quasi-elastic light scattering (QELS) in parallel to the SAXS measurements enables independent molecular weight validation and hydrodynamic radius estimates. This allows one to address sample monodispersity as well as conformational heterogeneity. The benefits of the current SEC-SAXS set-up are demonstrated on a set of selected standard proteins. The processed SEC-SAXS data and models are provided in the Small Angle Scattering Biological Data Bank (SASBDB) and are labeled as “bench-marked” datasets that include the unsubtracted data frames spanning the respective SEC elution profiles and corresponding MALLS-UV-RI-QELS data. These entries provide method developers with datasets suitable for testing purposes, in addition to an educational resource for SAS data analysis and modeling.

Functional characterization of quorum sensing LuxR-type transcriptional regulator, EasR in Enterobacter asburiae strain L1

Over the past decades, Enterobacter spp. have been identified as challenging and important pathogens. The emergence of multidrug-resistant Enterobacteria especially those that produce Klebsiella pneumoniae carbapenemase has been a very worrying health crisis. Although efforts have been made to unravel the complex mechanisms that contribute to the pathogenicity of different Enterobacter spp., there is very little information associated with AHL-type QS mechanism in Enterobacter spp. Signaling via N-acyl homoserine lactone (AHL) is the most common quorum sensing (QS) mechanism utilized by Proteobacteria. A typical AHL-based QS system involves two key players: a luxI gene homolog to synthesize AHLs and a luxR gene homolog, an AHL-dependent transcriptional regulator. These signaling molecules enable inter-species and intra-species interaction in response to external stimuli according to population density. In our recent study, we reported the genome of AHL-producing bacterium, Enterobacter asburiae strain L1. Whole genome sequencing and in silico analysis revealed the presence of a pair of luxI/R genes responsible for AHL-type QS, designated as easI/R, in strain L1. In a QS system, a LuxR transcriptional protein detects and responds to the concentration of a specific AHL controlling gene expression. In E. asburiae strain L1, EasR protein binds to its cognate AHLs, N-butanoyl homoserine lactone (C4-HSL) and N–hexanoyl homoserine lactone (C6-HSL), modulating the expression of targeted genes. In this current work, we have cloned the 693 bp luxR homolog of strain L1 for further characterization. The functionality and specificity of EasR protein in response to different AHL signaling molecules to activate gene transcription were tested and validated with β-galactosidase assays. Higher β-galactosidase activities were detected for cells harboring EasR, indicating EasR is a functional transcriptional regulator. This is the first report documenting the cloning and characterization of transcriptional regulator, luxR homolog of E. asburiae.

Rosetta-Enabled Structural Prediction of Permissive Loop Insertion Sites in Proteins

While loop motifs frequently play a major role in protein function, our understanding of how to rationally engineer proteins with novel loop domains remains limited. In the absence of rational approaches, the incorporation of loop domains often destabilizes proteins, thereby requiring massive screening and selection to identify sites that can accommodate loop insertion. We developed a computational strategy for rapidly scanning the entire structure of a scaffold protein to determine the impact of loop insertion at all possible amino acid positions. This approach is based on the Rosetta kinematic loop modeling protocol and was demonstrated by identifying sites in lipase that were permissive to insertion of the LAP peptide. Interestingly, the identification of permissive sites was dependent on the contribution of the residues in the near-loop environment on the Rosetta score and did not correlate with conventional structural features (e.g., B-factors). As evidence of this, several insertion sites (e.g., following residues 17, 47-49, and 108), which were predicted and confirmed to be permissive, interrupted helices, while others (e.g., following residues 43, 67, 116, 119, and 121), which are situated in loop regions, were nonpermissive. This approach was further shown to be predictive for β-glucosidase and human phosphatase and tensin homologue (PTEN), and to facilitate the engineering of insertion sites through in silico mutagenesis. By enabling the design of loop-containing protein libraries with high probabilities of soluble expression, this approach has broad implications in many areas of protein engineering, including antibody design, improving enzyme activity, and protein modification.

Computational characterisation of Toxoplasma gondii FabG (3-oxoacyl-[acyl-carrier-protein] reductase): a combined virtual screening and all-atom molecular dynamics simulation study

Toxoplasma gondii is an opportunistic obligate parasite, ubiquitous around the globe with seropositivity rates that range from 10% to 90% and infection by the parasite of pregnant women causes pre-natal death of the foetus in most cases and severe neurodegenerative syndromes in some. No vaccine is currently available, and since drug-resistance is common among T. gondii strains, discovering lead compounds for drug design using diverse tactics is necessary. In this study, the sole constituent isoform of an enzymatic 3-oxoacyl-[acyl-carrier-protein] reduction step in an apicoplast-located fatty acid biosynthesis pathway was chosen as a possible drug target. FASII is prokaryotic therefore, targeting it would pose fewer side-effects to human hosts. After a homology 3D modelling of TgFabG, a high-throughput virtual screening of 9867 compounds, the elimination of ligands was carried out by a flexible ligand molecular docking and 200 ns molecular dynamics simulations, with additional DCCM and PC plot analyses. Molecular Dynamics and related post-MD analyses of the top 3 TgFabG binders selected for optimal free binding energies, showed that L2 maintained strong H-bonds with TgFabG and facilitated structural reorientation expected of FabGs, namely an expansion of the Rossmann Fold and a flexible lid capping. The most flexible TgFabG sites were the α7 helix (the flexible lid region) and the β4-α4 and β5-α6 loops. For TgFabG-L2, the movements of these regions toward the active site enabled greater ligand stability. Thus, L2 ("Skimmine"; PubChem ID: 320361), was ultimately selected as the optimal candidate for the discovery of lead compounds for rational drug design.Communicated by Ramaswamy H. Sarma.

Determine the Potential Epitope Based Peptide Vaccine Against Novel SARS-CoV-2 Targeting Structural Proteins Using Immunoinformatics Approaches

Coronaviruses (CoVs) belong to the Coronaviridae-family. The genus Beta-coronaviruses, are enveloped positive strand RNA viruses with club-like spikes at the surface with a unique replication process and a large RNA genome (∼25 kb). CoVs are known as one of the major pathogenic viruses causing a variety of diseases in birds and mammals including humans (lethal respiratory dysfunctions). Recently, a new strain of coronavirus has been identified and named as SARS-CoV-2. A large number of COVID-19 (disease caused by SARS-CoV-2) cases are being diagnosed all over the World especially in China (Wuhan). COVID-19 showed high mortality rate exponentially, however, not even a single effective cure is being introduced yet against COVID-19. In the current study, immunoinformatics approaches were employed to predict the antigenic epitopes against COVID-19 for the development of a coronavirus peptide vaccine. Cytotoxic T-lymphocyte (CTL) and B-cell epitopes were predicted for SARS-CoV-2 coronavirus structural proteins (Spikes, Membrane, Envelope, and Nucleocapsid). The docking complexes of the top 10 epitopes having antigenic sites were analyzed led by binding affinity and binding interactional analyses of top ranked predicted peptides with the MHC-I HLA molecule. The predicted peptides may have potential to be used as peptide vaccine against COVID-19.

Structural Determinants within the Adenovirus Early Region 1A Protein Spacer Region Necessary for Tumorigenesis

It has long been established that group A human adenoviruses (HAdV-A12, -A18, and -A31) can cause tumors in newborn rodents, with tumorigenicity related to the presence of a unique spacer region located between conserved regions 2 and 3 within the HAdV-A12 early region 1A (E1A) protein. Group B adenoviruses are weakly oncogenic, whereas most of the remaining human adenoviruses are nononcogenic. In an attempt to understand better the relationship between the structure of the AdE1A spacer region and oncogenicity of HAdVs, the structures of synthetic peptides identical or very similar to the adenovirus 12 E1A spacer region were determined and found to be α-helical using nuclear magnetic resonance (NMR) spectroscopy. This contrasts significantly with some previous suggestions that this region is unstructured. Using available predictive algorithms, the structures of spacer regions from other E1As were also examined, and the extent of the predicted α-helix was found to correlate reasonably well with the tumorigenicity of the respective virus. We suggest that this may represent an as-yet-unknown binding site for a partner protein required for tumorigenesis.IMPORTANCE This research analyzed small peptides equivalent to a region within the human adenovirus early region 1A protein that confers, in part, tumor-inducing properties to various degrees on several viral strains in rats and mice. The oncogenic spacer region is α-helical, which contrasts with previous suggestions that this region is unstructured. The helix is characterized by a stretch of amino acids rich in alanine residues that are organized into a hydrophobic, or "water-hating," surface that is considered to form a major site of interaction with cellular protein targets that mediate tumor formation. The extent of α-helix in E1A from other adenovirus species can be correlated to a limited degree to the tumorigenicity of that virus. Some serotypes show significant differences in predicted structural propensity, suggesting that the amino acid type and physicochemical properties are also of importance.

High-Throughput Screening for Inhibitors of the SARS-CoV-2 Protease Using a FRET-Biosensor

The global SARS-CoV-2 pandemic started late 2019 and currently continues unabated. The lag-time for developing vaccines means it is of paramount importance to be able to quickly develop and repurpose therapeutic drugs. Protein-based biosensors allow screening to be performed using routine molecular laboratory equipment without a need for expensive chemical reagents. Here we present a biosensor for the 3-chymotrypsin-like cysteine protease from SARS-CoV-2, comprising a FRET-capable pair of fluorescent proteins held in proximity by a protease cleavable linker. We demonstrate the utility of this biosensor for inhibitor discovery by screening 1280 compounds from the Library of Pharmaceutically Active Compounds collection. The screening identified 65 inhibitors, with the 20 most active exhibiting sub-micromolar inhibition of 3CL^pro in follow-up EC₅₀ assays. The top hits included several compounds not previously identified as 3CL^pro inhibitors, in particular five members of a family of aporphine alkaloids that offer promise as new antiviral drug leads.

A kinetic coupling between protein unfolding and aggregation controls time-dependent solubility of the human myeloma antibody light chain

Protein aggregation is one of the most critical processes affecting protein solubility in various contexts-from protein therapeutics formulation to protein diseases. In general, time-dependent changes in protein solubility are complex kinetically driven processes that often involve a triggering event that consists of a protein unfolding/misfolding followed by the assembling of aggregation-competent protein species. In this study, we have examined the relation between stability and time-dependent solubility of the recombinant human antibody light chain, hLC, which was found to form renal tubular casts in the multiple myeloma patient. To analyze the aggregation quantitatively, the hLC stability and protein solubility assays were performed in vitro at elevated temperatures. A differential acceleration of the processes at high temperatures enabled us to dissect observed kinetics of irreversible hLC unfolding and aggregation. We find that for hLC these processes have different molecularity and activation energy barriers. While the irreversible unfolding of hLC is a unimolecular step with a substantial activation energy barrier of 260 kJ/mol, the aggregation is rate-limited by the bimolecular reaction, which is characterized by a lower activation energy barrier of 40 kJ/mol. By the combination of experimental assays at different temperatures, different protein concentrations and kinetic modeling using ordinary differential equations, we were able to extrapolate time-dependent protein solubility to temperatures where both unfolding and aggregation processes are strongly kinetically coupled. Our study enables mechanism-based evaluation and interpretation of different physico-chemical factors contributing to the hLC unfolding and aggregation and their effect on the formation of extracellular protein deposits.

Virus database annotations assist in tracing information on patients infected with emerging pathogens

The global pandemic of SARS-CoV-2 has disrupted human social activities. In restarting economic activities, successive outbreaks by new variants are concerning. Here, we evaluated the applicability of public database annotations to estimate the virulence, transmission trends and origins of emerging SARS-CoV-2 variants. Among the detectable multiple mutations, we retraced the mutation in the spike protein. With the aid of the protein database, structural modelling yielded a testable scientific hypothesis on viral entry to host cells. Simultaneously, annotations for locations and collection dates suggested that the variant virus emerged somewhere in the world in approximately February 2020, entered the USA and propagated nationwide with periodic sampling fluctuation likely due to an approximately 5-day incubation delay. Thus, public database annotations are useful for automated elucidation of the early spreading patterns in relation to human behaviours, which should provide objective reference for local governments for social decision making to contain emerging substrains. We propose that additional annotations for past paths and symptoms of the patients should further assist in characterizing the exact virulence and origins of emerging pathogens.

Structure-Guided Designing and Evaluation of Peptides Targeting Bacterial Transcription

The mycobacterial RNA polymerase (RNAP) is an essential and validated drug target for developing antibacterial drugs. The β-subunit of Mycobacterium tuberculosis (Mtb) RNAP (RpoB) interacts with an essential and global transcription factor, CarD, and confers antibiotic and oxidative stress resistance to Mtb. Compromising the RpoB/CarD interactions results in the killing of mycobacteria, hence disrupting the RpoB/CarD interaction has been proposed as a novel strategy for the development of anti-tubercular drugs. Here, we describe the first approach to rationally design and test the efficacy of the peptide-based inhibitors which specifically target the conserved PPI interface between the bacterial RNAP β/transcription factor complex. We performed in silico protein-peptide docking studies along with biochemical assays to characterize the novel peptide-based inhibitors. Our results suggest that the top ranked peptides are highly stable, soluble in aqueous buffer, and capable of inhibiting transcription with IC₅₀ > 50 μM concentration. Using peptide-based molecules, our study provides the first piece of evidence to target the conserved RNAP β/transcription factor interface for designing new inhibitors. Our results may hence form the basis to further improve the potential of these novel peptides in modulating bacterial gene expression, thus inhibiting bacterial growth and combating bacterial infections.

Designing a multi-epitope peptide based vaccine against SARS-CoV-2

COVID-19 pandemic has resulted in 16,114,449 cases with 646,641 deaths from the 217 countries, or territories as on July 27th 2020. Due to multifaceted issues and challenges in the implementation of the safety and preventive measures, inconsistent coordination between societies-governments and most importantly lack of specific vaccine to SARS-CoV-2, the spread of the virus that initially emerged at Wuhan is still uprising after taking a heavy toll on human life. In the present study, we mapped immunogenic epitopes present on the four structural proteins of SARS-CoV-2 and we designed a multi-epitope peptide based vaccine that, demonstrated a high immunogenic response with a vast application on world’s human population. On codon optimization and in-silico cloning, we found that candidate vaccine showed high expression in E. coli and immune simulation resulted in inducing a high level of both B-cell and T-cell mediated immunity. The results predicted that exposure of vaccine by administrating three injections significantly subsidized the antigen growth in the system. The proposed candidate vaccine found promising by yielding desired results and hence, should be validated by practical experimentations for its functioning and efficacy to neutralize SARS-CoV-2.

Molecular basis for the distinct cellular functions of the Lsm1-7 and Lsm2-8 complexes

Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1-7 complex initiates mRNA decay, while the nuclear Lsm2-8 complex acts as a chaperone for U6 spliceosomal RNA. It has been unclear how these complexes perform their distinct functions while differing by only one out of seven subunits. Here, we elucidate the molecular basis for Lsm-RNA recognition and present four high-resolution structures of Lsm complexes bound to RNAs. The structures of Lsm2-8 bound to RNA identify the unique 2',3' cyclic phosphate end of U6 as a prime determinant of specificity. In contrast, the Lsm1-7 complex strongly discriminates against cyclic phosphates and tightly binds to oligouridylate tracts with terminal purines. Lsm5 uniquely recognizes purine bases, explaining its divergent sequence relative to other Lsm subunits. Lsm1-7 loads onto RNA from the 3' end and removal of the Lsm1 carboxy-terminal region allows Lsm1-7 to scan along RNA, suggesting a gated mechanism for accessing internal binding sites. These data reveal the molecular basis for RNA binding by Lsm proteins, a fundamental step in the formation of molecular assemblies that are central to eukaryotic mRNA metabolism.

mCSM-membrane: predicting the effects of mutations on transmembrane proteins

Significant efforts have been invested into understanding and predicting the molecular consequences of mutations in protein coding regions, however nearly all approaches have been developed using globular, soluble proteins. These methods have been shown to poorly translate to studying the effects of mutations in membrane proteins. To fill this gap, here we report, mCSM-membrane, a user-friendly web server that can be used to analyse the impacts of mutations on membrane protein stability and the likelihood of them being disease associated. mCSM-membrane derives from our well-established mutation modelling approach that uses graph-based signatures to model protein geometry and physicochemical properties for supervised learning. Our stability predictor achieved correlations of up to 0.72 and 0.67 (on cross validation and blind tests, respectively), while our pathogenicity predictor achieved a Matthew's Correlation Coefficient (MCC) of up to 0.77 and 0.73, outperforming previously described methods in both predicting changes in stability and in identifying pathogenic variants. mCSM-membrane will be an invaluable and dedicated resource for investigating the effects of single-point mutations on membrane proteins through a freely available, user friendly web server at http://biosig.unimelb.edu.au/mcsm_membrane.

Characterization of essential domains in HSD17B13 for cellular localization and enzymatic activity

Human genetic studies recently identified an association of SNPs in the 17-β hydroxysteroid dehydrogenase 13 (HSD17B13) gene with alcoholic and nonalcoholic fatty liver disease development. Mutant HSD17B13 variants devoid of enzymatic function have been demonstrated to be protective from cirrhosis and liver cancer, supporting the development of HSD17B13 as a promising therapeutic target. Previous studies have demonstrated that HSD17B13 is a lipid droplet (LD)-associated protein. However, the critical domains that drive LD targeting or determine the enzymatic activity have yet to be defined. Here we used mutagenesis to generate multiple truncated and point-mutated proteins and were able to demonstrate in vitro that the N-terminal hydrophobic domain, PAT-like domain, and a putative α-helix/β-sheet/α-helix domain in HSD17B13 are all critical for LD targeting. Similarly, we characterized the predicted catalytic, substrate-binding, and homodimer interaction sites and found them to be essential for the enzymatic activity of HSD17B13, in addition to our previous identification of amino acid P260 and cofactor binding site. In conclusion, we identified critical domains and amino acid sites that are essential for the LD localization and protein function of HSD17B13, which may facilitate understanding of its function and targeting of this protein to treat chronic liver diseases.

Designing an efficient multi-epitope vaccine displaying interactions with diverse HLA molecules for an efficient humoral and cellular immune response to prevent COVID-19 infection

Background

The novel SARS-CoV-2 coronavirus, the causative agent of the ongoing pandemic COVID-19 disease continues to infect people globally and has infected millions of humans worldwide. However, no effective vaccine against this virus exists.

Method

Using Immunoinformatics, epitopic sequences from multiple glycoproteins that play crucial role in pathogenesis were identified. Particularly, epitopes were mapped from conserved receptor-binding domain of spike protein which have been experimentally validated in SARS-CoV-1 as a promising target for vaccine development.

Results

A multi-epitopic vaccine construct comprising of B-cell, CTL, HTL epitopes was developed along with fusion of adjuvant and linkers. The epitopes identified herein are reported for the first time and were predicted to be highly antigenic, stable, nonallergen, nontoxic and displayed conservation across several SARS-CoV-2 isolates from different countries. Additionally, the epitopes associated with maximum HLA alleles and population coverage analysis shows the proposed epitopes would be a relevant representative of large proportion of the world population. A reliable three-dimensional structure of the vaccine construct was developed. Consequently, docking and molecular-dynamics simulation ensured the stable interaction between vaccine and innate-immune receptor.

The Molecular and Functional Characterization of the Durum Wheat Lipoxygenase TdLOX2 Suggests Its Role in Hyperosmotic Stress Response

In plants, lipoxygenases (LOXs) are involved in various processes, such as growth, development, and response to stress cues. In the present study, the expression pattern of six durum wheat LOX-encoding genes (TdLpx-B1.1, TdLpx-B1.2, TdLpx-A2, TdLpx-B2, TdLpx-A3 and TdLpx-B3) under hyperosmotic stress was investigated. With osmotic (0.42 M mannitol) and salt (0.21 M NaCl) stress imposed at the early stages of seedling growth, a strong induction of the TdLpx-A2 gene expression in the shoots paralleled an equally strong increase in the LOX activity. Enhanced levels of malondialdehyde (MDA) and increased rates of superoxide anion generation were also observed as a result of the stress imposition. Sequence analysis of the TdLOX2 encoded by the TdLpx-A2 gene revealed that it belonged to the type-1 9-LOX group. When overexpressed in E. coli, TdLOX2 exhibited normal enzyme activity, high sensitivity to specific LOX inhibitors, with 76% and 99% inhibition by salicylhydroxamic and propyl gallate, respectively, and a preference for linoleic acid as substrate, which was converted exclusively to its corresponding 13-hydroperoxide. This unexpected positional specificity could be related to the unusual TV/K motif that in TdLOX2 replaces the canonical TV/R motif of 9-LOXs. Treatment of seedlings with propyl gallate strongly suppressed the increase in LOX activity induced by the hyperosmotic stress; the MDA accumulation was also reduced but less markedly, whereas the rate of superoxide anion generation was even more increased. Overall, our findings suggest that the up-regulation of the TdLpx-A2 gene is a component of the durum wheat response to hyperosmotic stress and that TdLOX2 may act by counteracting the excessive generation of harmful reactive oxygen species responsible for the oxidative damages that occur in plants under stress.

A plant-derived cocaine hydrolase prevents cocaine overdose lethality and attenuates cocaine-induced drug seeking behavior

Cocaine use disorders include short-term and acute pathologies (e.g. overdose) and long-term and chronic disorders (e.g. intractable addiction and post-abstinence relapse). There is currently no available treatment that can effectively reduce morbidity and mortality associated with cocaine overdose or that can effectively prevent relapse in recovering addicts. One recently developed approach to treat these problems is the use of enzymes that rapidly break down the active cocaine molecule into inactive metabolites. In particular, rational design and site-directed mutagenesis transformed human serum recombinant butyrylcholinesterase (BChE) into a highly efficient cocaine hydrolase with drastically improved catalytic efficiency toward (-)-cocaine. A current drawback preventing the clinical application of this promising enzyme-based therapy is the lack of a cost-effective production strategy that is also flexible enough to rapidly scale-up in response to continuous improvements in enzyme design. Plant-based expression systems provide a unique solution as this platform is designed for fast scalability, low cost and the advantage of performing eukaryotic protein modifications such as glycosylation. A Plant-derived form of the Cocaine Super Hydrolase (A199S/F227A/S287G/A328W/Y332G) we designate PCocSH protects mice from cocaine overdose, counters the lethal effects of acute cocaine overdose, and prevents reinstatement of extinguished drug-seeking behavior in mice that underwent place conditioning with cocaine. These results demonstrate that the novel PCocSH enzyme may well serve as an effective therapeutic for cocaine use disorders in a clinical setting.

ppGpp Coordinates Nucleotide and Amino-Acid Synthesis in E. coli During Starvation

(p)ppGpp is a nucleotide messenger universally produced in bacteria following nutrient starvation. In E. coli, ppGpp inhibits purine nucleotide synthesis by targeting several different enzymes, but the physiological significance of their inhibition is unknown. Here, we report the structural basis of inhibition for one target, Gsk, the inosine-guanosine kinase. Gsk creates an unprecedented, allosteric binding pocket for ppGpp by restructuring terminal sequences, which restrains conformational dynamics necessary for catalysis. Guided by this structure, we generated a chromosomal mutation that abolishes Gsk regulation by ppGpp. This mutant strain accumulates abnormally high levels of purine nucleotides following amino-acid starvation, compromising cellular fitness. We demonstrate that this unrestricted increase in purine nucleotides is detrimental because it severely depletes pRpp and essential, pRpp-derived metabolites, including UTP, histidine, and tryptophan. Thus, our results reveal the significance of ppGpp's regulation of purine nucleotide synthesis and a critical mechanism by which E. coli coordinates biosynthetic processes during starvation.

Genome-wide characterization of the GRF family and their roles in response to salt stress in Gossypium

BACKGROUND

Cotton (Gossypium spp.) is the most important world-wide fiber crop but salt stress limits cotton production in coastal and other areas. Growth regulation factors (GRFs) play regulatory roles in response to salt stress, but their roles have not been studied in cotton under salt stress.

RESULTS

We identified 19 GRF genes in G. raimondii, 18 in G. arboreum, 34 in G. hirsutum and 45 in G. barbadense, respectively. These GRF genes were phylogenetically analyzed leading to the recognition of seven GRF clades. GRF genes from diploid cottons (G. raimondii and G. arboreum) were largely retained in allopolyploid cotton, with subsequent gene expansion in G. barbadense relative to G. hirsutum. Most G. hirsutum GRF (GhGRF) genes are preferentially expressed in young and growing tissues. To explore their possible role in salt stress, we used qRT-PCR to study expression responses to NaCl treatment, showing that five GhGRF genes were down-regulated in leaves. RNA-seq experiments showed that seven GhGRF genes exhibited decreased expression in leaves under NaCl treatment, three of which (GhGRF3, GhGRF4, and GhGRF16) were identified by both RNA-seq and qRT-PCR. We also identified six and three GRF genes that exhibit decreased expression under salt stress in G. arboreum and G. barbadense, respectively. Consistent with its lack of leaf withering or yellowing under the salt treatment conditions, G. arboreum had better salt tolerance than G. hirsutum and G. barbadense. Our results suggest that GRF genes are involved in salt stress responses in Gossypium.

CONCLUSION

In summary, we identified candidate GRF genes that were involved in salt stress responses in cotton.

The barley lectin, horcolin, binds high-mannose glycans in a multivalent fashion, enabling high-affinity, specific inhibition of cellular HIV infection

N-Linked glycans are critical to the infection cycle of HIV, and most neutralizing antibodies target the high-mannose glycans found on the surface envelope glycoprotein-120 (gp120). Carbohydrate-binding proteins, particularly mannose-binding lectins, have also been shown to bind these glycans. Despite their therapeutic potency, their ability to cause lymphocyte proliferation limits their application. In this study, we report one such lectin named horcolin (Hordeum vulgare lectin), seen to lack mitogenicity owing to the divergence in the residues at its carbohydrate-binding sites, which makes it a promising candidate for exploration as an anti-HIV agent. Extensive isothermal titration calorimetry experiments reveal that the lectin was sensitive to the length and branching of mannooligosaccharides and thereby the total valency. Modeling and simulation studies demonstrate two distinct modes of binding, a monovalent binding to shorter saccharides and a bivalent mode for higher glycans, involving simultaneous interactions of multiple glycan arms with the primary carbohydrate-binding sites. This multivalent mode of binding was further strengthened by interactions of core mannosyl residues with a secondary conserved site on the protein, leading to an exponential increase in affinity. Finally, we confirmed the interaction of horcolin with recombinant gp120 and gp140 with high affinity and inhibition of HIV infection at nanomolar concentrations without mitogenicity.