Homology Modeling and Evaluation of Sars-Cov-2 Spike Protein Mutant

Severe acute respiratory syndrome coronavirus 2 (SARS‐Cov-2), a global pandemic, affected the world, increasing every day. A mutated variant D614G, showing more virulence and transmission, was studied for forecasting the emergence of more virulent and pathogenic viral strains. This study focuses on structure modeling and validation. Characterization of proteins homologous to wild spike protein was done, and homology models of the mutated variant were modeled using these proteins. Validation of models was done using Ramachandran plot and ERRAT plot. Molecular dynamics simulation was used to validate the stability of the models, and binding affinity of these models were estimated by molecular docking with an approved antiviral drug. Docked complexes were studied and the best model was selected. Molecular dynamics simulation was used to estimate the stability of the docked complex. The model of 6VXX, a homologous of wild spike protein, was found to be stable with the interaction of the antiviral drug from this study.

Immunogenic Potency of a Chimeric Protein Comprising InvH and IpaD against Salmonella and Shigella spp

Shigella and Salmonella cause serious problems in many subjects, including young children and the elderly, especially in developing countries. Chimeric proteins carrying immunogens increase immune response. In-silico tools are applied to design vaccine candidates. Invasion plasmid antigens D (ipaD) gene is one of the Shigella virulence factors. The N-terminal region of the IpaD plays a significant role in invading the host cell. Invasion protein H (invH) gene plays important role in bacterial adherence and entry into epithelial cells. A recombinant chimeric construct, containing IpaD and InvH was designed and used as a vaccine candidate against Shigella and Salmonella enteritidis. After bioinformatics assessments, the construct was designed, synthesized, and expressed in E.coli. Chimeric protein, IpaD, and InvH were purified with Ni-NTA chromatography. Purified proteins were confirmed with western blotting and then were injected into separate mice groups. The antibody titer was estimated with an enzyme-linked immunosorbent assay (ELISA). Mice were challenged with 10, 100, and 1000 LD50 of Salmonella, and the sereny test was performed for Shigella. The Codon adaptation index of the chimeric gene was increased to 0.84. Validation results showed that 97.9% of residues lie in the favored or additional allowed region of the Ramachandran plot. A significant antibody rise was observed in all test groups. The immunized mice with chimer and InvH could tolerate 100 LD50 of Salmonella. In the sereny test, the application of bacteria treated with immunized mice sera of both antigens showed no infection in Guinea pigs' eyes. The recombinant protein could protect animal models against Salmonella and Shigella and therefore can be considered as a suitable vaccine candidate against these two pathogens.

The structure of an archaeal oligosaccharyltransferase provides insight into the strict exclusion of proline from the N-glycosylation sequon

Oligosaccharyltransferase (OST) catalyzes oligosaccharide transfer to the Asn residue in the N-glycosylation sequon, Asn-X-Ser/Thr, where Pro is strictly excluded at position X. Considering the unique structural properties of proline, this exclusion may not be surprising, but the structural basis for the rejection of Pro residues should be explained explicitly. Here we determined the crystal structure of an archaeal OST in a complex with a sequon-containing peptide and dolichol-phosphate to a 2.7 Å resolution. The sequon part in the peptide forms two inter-chain hydrogen bonds with a conserved amino acid motif, TIXE. We confirmed the essential role of the TIXE motif and the adjacent regions by extensive alanine-scanning of the external loop 5. A Ramachandran plot revealed that the ring structure of the Pro side chain is incompatible with the ϕ backbone dihedral angle around −150° in the rigid sequon-TIXE structure. The present structure clearly provides the structural basis for the exclusion of Pro residues from the N-glycosylation sequon.

Protein world and hemochiralty

Protein world hypothesis and the origin of homochiralty are described. By using enzyme catalyzing itself, L-amino acid can replicate. L-amino acid also catalyze D-sugar production. By using Ramachandran plot, L-amino acid is favored for generating right alpha helix and beta sheet. Thus, homochiralty of earth happened.

Molecular Docking Analysis of the T450A Mutation of the Gene rpoB Mycobacterium leprae from Leprosy Patients in Papua, West Papua and North Maluku, Indonesia

Leprosy persists to be a health problem in Indonesia, especially in the provinces of North Maluku, West Papua and Papua. Early diagnosis and complete treatment with multidrug therapy (MDT) remain the key strategy for reducing the disease burden. One of the major components of MDT is rifampicin which in certain cases in several countries, M. leprae resistance to this drug issue has been reported albeit only a few. This research aimed to detect and analyze polymorphism in M. leprae rpoB gene that was isolated from leprosy patients in three provinces: North Maluku Province, West Papua Province and Papua Province, Indonesia. The identification of mutations in the M. leprae rpoB gene was carried out by aligning the results of DNA sequencing with the reference strain. The 3D structure of rpoB was derived using the Swiss Model. The T450A, S456L, and H451Y variants of RNA Polymerase B subunits were constructed using FoldX based on the wild-type structure. The structures were repaired, and protein stability was evaluated using foldX under the Yasara viewer. The QC of the rpoB M. leprae homology models was conducted with Ramachandran Plot modeling using PROCHECK. The difference in binding affinity between native protein and T450A, S456L, and H45I variants were analyzed using molecular docking. rpoB gene of M. leprae contains a mutation found in nucleotide of 1348 bp. The mutation triggered the conversion of the amino acid Threonine to Alanine in the amino acid to 450 rpoB subunit B. The structure of 3D RNA Polymerase Subunit B was constructed using rpoB Mycobacterium tuberculosis with PDB code 5UH5 as template. According to Ramachandran Plot, the percentage of residues in the most favored regions are 91.9%, and there was no significant number of residues in the disallowed regions. The results of molecular docking showed that the T450A variant had the same binding affinity with the native protein which was -8.9 kcal. Binding affinity on the S456L and H451Y variants increased by -7.3 kcal and -8.2 kcal, respectively. According to Molecular Docking analysis, T450A variant did not affect the energy binding between RNA polymerase and rifampicin.

Structural basis for the strict exclusion of proline from the N-glycosylation sequon

Oligosaccharyltransferase (OST) catalyzes oligosaccharide transfer to the Asn residue in the N-glycosylation sequon, Asn-X-Ser/Thr, where Pro is strictly excluded at position X. Considering the unique structural properties of proline, this exclusion may not be surprising, but the structural basis for the rejection of Pro residues should be explained explicitly. The crystal structure of an archaeal OST in a complex with a sequon-containing peptide and dolichol-phosphate was determined to a 2.7 Å resolution. The sequon part in the peptide forms two inter-chain hydrogen bonds with a conserved amino acid motif, TIXE. We confirmed the essential role of the TIXE motif and the adjacent regions by extensive alanine-scanning of the external loop 5. A Ramachandran plot revealed that the ring structure of the Pro side chain is incompatible with the φ backbone dihedral angle around -150° in the rigid sequon-TIXE structure.

LAHMA: structure analysis through local annotation of homology-matched amino acids

Comparison of homologous structure models is a key step in analyzing protein structure. With a wealth of homologous structures, comparison becomes a tedious process, and often only a small (user-biased) selection of data is used. A multitude of structural superposition algorithms are then typically used to visualize the structures together in 3D and to compare them. Here, the Local Annotation of Homology-Matched Amino acids (LAHMA) website (https://lahma.pdb-redo.eu) is presented, which compares any structure model with all of its close homologs from the PDB-REDO databank. LAHMA displays structural features in sequence space, allowing users to uncover differences between homologous structure models that can be analyzed for their relevance to chemistry or biology. LAHMA visualizes numerous structural features, also allowing one-click comparison of structure-quality plots (for example the Ramachandran plot) and `in-browser' structural visualization of 3D models.

Structural and Functional Annotation of Uncharacterized Protein NCGM946K2_146 of Mycobacterium Tuberculosis: An In-Silico Approach

The human pathogen Mycobacterium tuberculosis (MTB) is indeed one of the renowned, important, longtime infectious diseases, tuberculosis (TB). Interestingly, MTB infection has become one of the world’s leading causes of human death. In trehalose synthase, the protein NCGM 946K2 146 found in MTB has an important role. For carbohydrate transport and metabolism, trehalose synthase is required. The protein is not clarified yet, though. In this research, an in silico approach was, therefore, formulated for functional and structural documentation of the uncharacterized protein NCGM946K2_146.Three distinct servers, including Modeller, Phyre2, and Swiss Model, were used to evaluate the predicted tertiary structure. The top materials are selected using structural evaluations conducted with the analysis of Ramachandran Plot, Swiss-Model Interactive Workplace, ProSA-web, Verify 3D, and Z scores. This analysis aimed to uncover the value of the NCGM946K2_146 protein of MTB. This research will, therefore, improve our pathogenesis awareness and give us a chance to target the protein compound.

In silico Structural Modelling of Ribokinase from Salmonella Typhi

The knowledge of identifiable differences in the metabolism and macromolecular structure between infective agents and their host can be exploited in rational drug design. Ribokinase, an enzyme that plays an important role in the phosphorylation of several metabolites is one of such that can be exploited. This study was therefore aimed at structurally modelling ribokinase from Salmonella Typhi, the causative agent of typhoid fever, with several known multi-drug resistant strains. NCBI BLASTp was carried out against Protein Data Bank (PDB) to run a similarity search. Multiple sequence alignment between the query sequence and the templates was carried out using clustal omega and MEGA6.0 software. The amino acid sequence was submitted to modelling servers. The predicted models from the servers were evaluated with RAMPAGE and superimposed in the template using PyMOL. Model with highest Ramachandran plot score was further validated. BLASTp result showed low identity of (41%) with pyridoxal kinase from Trypanosoma brucei in PDB database. Conserved sequence motifs were confirmed. Template 4X8F was chosen based on its high identity, query cover and appearance in the modeling tools. Swiss model showed best Ramachandran plot score (94.9%). ERRAT analysis showed quality factor: 92.9078 and VERIFY3D server showed that 84.43% of the residues have an average score of 3D/ ID score >=0.2. Superimposition confirmed the alignment of the active site residues having aspartic acid as the catalytic residue. This study can serve as a means for rational drug design for the treatment of typhoid fever.

Microarray data analysis, structure prediction and in silico docking of drugs for inhibiting the over expression of High Mobility Group A1 in human malignant neoplasias

The High Mobility Group A1 (HMGA1) gene over expression has been widely observed in various types of cancers. The raw data for microarray data analysis was obtained from the dataset record GDS3525. The SOM and K-means of the Genesis led to the identification of two clusters (each consisting of 30 genes) bearing HMGA1 gene. This on further analysis resulted into identification of 14 similar genes by Easy M-A. The evolutionary similarity of HMGA1 and GORASP2 is clearly observed in the Phylogenetic Tree. Due to the absence of precise structures, the homology modeling was done by using EasyModeller and the resulting models of proteins HMGA1 and GORASP2 were validated by Ramachandran plot. These models were further put to loop optimization by Modloop and the output models were assessed by Ramachandran plot (Rampage) and through SAVS (Procheck). The molecular docking was done by using Autodock, this resulted in two ligands, DB11641 (Vinflunine) and DB12674 (Lurbinectedin), showing potential for the effective treatment of various types of cancers characterized by the over expression of HMGA1 and GORASP2.