The human spike protein sequences from Asia, Africa, Europe, North America, South America, and Oceania were analyzed by comparing with the reference severe acute respiratory syndrome coronavirus‐2 ...(SARS‐CoV‐2) protein sequence from Wuhan‐Hu‐1, China. Out of 10333 spike protein sequences analyzed, 8155 proteins comprised one or more mutations. A total of 9654 mutations were observed that correspond to 400 distinct mutation sites. The receptor binding domain (RBD) which is involved in the interactions with human angiotensin‐converting enzyme‐2 (ACE‐2) receptor and causes infection leading to the COVID‐19 disease comprised 44 mutations that included residues within 3.2 Å interacting distance from the ACE‐2 receptor. The mutations observed in the spike proteins are discussed in the context of their distribution according to the geographical locations, mutation sites, mutation types, distribution of the number of mutations at the mutation sites and mutations at the glycosylation sites. The density of mutations in different regions of the spike protein sequence and location of the mutations in protein three‐dimensional structure corresponding to the RBD are discussed. The mutations identified in the present work are important considerations for antibody, vaccine, and drug development.
Quantum chemical calculations have been performed at the M06–2X/6–31G(d,p) level of theory to investigate the strength and nature of interactions between the active site amino acids at positions 25 ...and 30 with darunavir (DRV) inhibitor of two native (D25 and D30 in 4LL3, 1T3R) and five mutant (N25 in 3BVB, 3SO9; N30 in 2F80, 3LZV, 3UCB) HIV–1 proteases. Molecular orbitals HOMO and LUMO noted down upon the M06–2X/6–31G(d,p) level optimized amino acid–DRV geometries helped us explain which region of the inhibitor has the ability to interact with the amino acid more effectively. This analysis of the molecular orbitals allowed us to explore the nature of the interactions present between active site amino acids and the DRV in native and mutated proteins. The electrostatic potential surface maps generated for the amino acid–DRV complexes investigated the extent of interactions within the active site of the protein. Natural bond order analysis performed on the optimized geometries suggested that the extent of charge transfer helps in determining the stability of the complexes, which is very important for drug design.
A variety of coronaviruses (CoVs) have infected humans and caused mild to severe respiratory diseases that could result in mortality. The human CoVs (HCoVs) belong to the genera of α- and β-CoVs that ...originate in rodents and bats and are transmitted to humans via zoonotic contacts. The binding of viral spike proteins to the host cell receptors is essential for mediating fusion of viral and host cell membranes to cause infection. The SARS-CoV-2 originated in bats (RaTG13 SARS-CoV) and is transmitted to humans via pangolins. The presence of 'PRRA' sequence motif in SARS-CoV-2 spike proteins from human, dog, cat, mink, tiger and lion suggests a common viral entry mechanism into host cells. In this review, we discuss structural features of HCoV spike proteins and recognition of host protein and carbohydrate receptors.
Coronavirus disease 2019 (COVID‐19) is a pandemic infectious disease caused by novel severe acute respiratory syndrome coronavirus‐2 (SARS CoV‐2). The SARS CoV‐2 is transmitted more rapidly and ...readily than SARS CoV. Both, SARS CoV and SARS CoV‐2 via their glycosylated spike proteins recognize the human angiotensin converting enzyme‐2 (ACE‐2) receptor. We generated multiple sequence alignments and phylogenetic trees for representative spike proteins of SARS CoV and SARS CoV‐2 from various host sources in order to analyze the specificity in SARS CoV‐2 spike proteins required for causing infection in humans. Our results show that among the genomes analyzed, two sequence regions in the N‐terminal domain “MESEFR” and “SYLTPG” are specific to human SARS CoV‐2. In the receptor‐binding domain, two sequence regions “VGGNY“ and ”EIYQAGSTPCNGV” and a disulfide bridge connecting 480C and 488C in the extended loop are structural determinants for the recognition of human ACE‐2 receptor. The complete genome analysis of representative SARS CoVs from bat, civet, human host sources, and human SARS CoV‐2 identified the bat genome (GenBank code: MN996532.1) as closest to the recent novel human SARS CoV‐2 genomes. The bat SARS CoV genomes (GenBank codes: MG772933 and MG772934) are evolutionary intermediates in the mutagenesis progression toward becoming human SARS CoV‐2.
BCR-ABL kinase domain inhibition can be used to treat chronic myeloid leukemia. The inhibitors such as imatinib, dasatinib and nilotinib are effective drugs but are resistant to some BCR-ABL ...mutations. The pan-BCR-ABL kinase inhibitor ponatinib exhibits potent activity against native, T315I, and all other clinically relevant mutants, and showed better inhibition than the previously known inhibitors. We have studied the molecular dynamics simulations and calculated solvated interaction energies of native and fourteen mutant BCR-ABL kinases (M244V, G250E, Q252H, Y253F, Y253H, E255K, E255V, T315A, T315I, F317L, F317V, M351T, F359V and H396P) complexed with ponatinib. These studies revealed that the interactions between ponatinib and individual residues in BCR-ABL kinase are also affected due to the remote residue mutations. We report that some residues, Met244, Lys245, Gln252, Gly254, Leu370 and Leu298 do not undergo any conformational changes, while the fluctuations in residues from P-loop, β3-, β5- strands and αC- helix are mainly responsible for ponatinib binding to native and all mutant BCR-ABL kinases. Our work provides the molecular mechanisms of native and mutant BCR-ABL kinases inhibition by ponatinib at atomic level that has not been studied before.
COVID-19 disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) has resulted in tremendous loss of lives across the world and is continuing to do so. Extensive work is under ...progress to develop inhibitors which can prevent the disease by arresting the virus in its life cycle. One such way is by targeting the main protease of the virus which is crucial for the cleavage and conversion of polyproteins into functional units of polypeptides. In this endeavor, our effort was to identify hit molecule inhibitors for SARS-CoV2 main protease using fragment-based drug discovery (FBDD), based on the available crystal structure of chromene-based inhibitor (PDB_ID: 6M2N). The designed molecules were validated by molecular docking and molecular dynamics simulations. The stability of the complexes was further assessed by calculating their binding free energies, normal mode analysis, mechanical stiffness, and principal component analysis.
PLK-2 is a serine/threonine protein kinase and plays a crucial role in cell cycle regulation; due to its pivotal function, this enzyme is approved as cancer drug target. We used BI-2536 a PLK-1/PLK-2 ...inhibitor to build a pharmacophore model and applied in the virtual screening of ZINC database to retrieve new molecules that bind the active site of PLK-2 environment with a high fit value. The molecules that do not fit the enzyme active site environment were subjected to conformation enrichment by generation of conformations in the active site environment by molecular docking, and the molecules with new scaffold that did not pass into the active site from molecular docking were subjected to molecular pruning to delete bulky substituents that prevent the molecules from binding. Molecular docking was used to find the binding pose of the selected molecules into active site of PLK-2; all screened-in hit molecules make favorable non-bonding interactions with PLK-2 active site similar to the reference inhibitor. Molecular dynamics simulations, the binding free energy calculations of the complexes, and the stability of hydrogen bonding interactions further revealed the usefulness of these screened compounds as suitable hit molecules for inhibition of PLK-2.
The PE and PPE proteins first reported in the genome sequence of Mycobacterium tuberculosis strain H37Rv are now identified in all mycobacterial species. The PE-PPE domain (Pfam ID: PF08237) is a 225 ...amino acid residue conserved region located towards the C-terminus of some PE and PPE proteins and hypothetical proteins. Our in-silico sequence analysis revealed that this domain is present in all Mycobacteria, some Rhodococcus and Nocardia farcinica genomes. This domain comprises a pentapeptide sequence motif GxSxG/S at the N-terminus and conserved amino acid residues Ser, Asp and His that constitute a catalytic triad characteristic of lipase, esterase and cutinase activity. The fold prediction and comparative modeling of the 3-D structure of the PE-PPE domain revealed a "serine α/β hydrolase" structure with a central β-sheet flanked by α-helices on either side. The structure comprises a lid insertion with a closed structure conformation and has a solvent inaccessible active site. The oxyanion hole that stabilizes the negative charge on the tetrahedral intermediate has been identified. Our findings add to the growing list of serine hydrolases in mycobacterium, which are essential for the maintenance of their impermeable cell wall and virulence. These results provide the directions for the design of experiments to establish the function of PE and PPE proteins.
We describe the improvement of transglycosylation (TG) by chitinase D from Serratia proteamaculans (SpChiD). The SpChiD produced a smaller quantity of TG products for up to 90 min with 2 mm ...chitotetraose as the substrate and subsequently produced only hydrolytic products. Of the five residues targeted at the catalytic center, E159D resulted in substantial loss of both hydrolytic and TG activities. Y160A resulted in a product profile similar to SpChiD and a rapid turnover of substrate with slightly increased TG activity. The rest of the three mutants, M226A, Y228A, and R284A, displayed improved TG and decreased hydrolytic ability. Four of the five amino acid substitutions, F64W, F125A, G119S, and S116G, at the catalytic groove increased TG activity, whereas W120A completely lost the TG activity with a concomitant increase in hydrolysis. Mutation of Trp-247 at the solvent-accessible region significantly reduced the hydrolytic activity with increased TG activity. The mutants M226A, Y228A, F125A, S116G, F64W, G119S, R284A, and W247A accumulated approximately double the concentration of TG products like chitopentaose and chitohexaose, compared with SpChiD. The double mutant E159D/F64W regained the activity with accumulation of 6.0% chitopentaose at 6 h, similar to SpChiD at 30 min. Loss of chitobiase activity was unique to Y228A. Substitution of amino acids at the catalytic center and/or groove substantially improved the TG activity of SpChiD, both in terms of the quantity of TG products produced and the extended duration of TG activity.
SpChiD, a family 18 glycosyl hydrolase, transglycosylates chitooligosaccharides.
Transglycosylation of SpChiD was improved in terms of the quantity of TG products produced and the extended duration of TG.
The new findings unravel possibilities of modulating chitinases for improved transglycosylation.
Variants of SpChiD can be used to develop a bio-process for large scale production of longer chain chitooligosaccharides.
The PE and PPE multigene families, first discovered during the sequencing of M. tuberculosis H37Rv genome are responsible for antigenic variation and have been shown to induce increased humoral and ...cell mediated immune response in the host. Using the bioinformatics tools, we had earlier reported that the 225 amino acid residue PE-PPE domain (Pfam: PF08237) common to some PE and PPE proteins has a "serine α/β hydrolase" fold and conserved Ser, Asp and His catalytic triad characteristic of lipase, esterase and cutinase activities. In order to prove experimentally that PE-PPE domain is indeed a serine hydrolase, we have cloned the full-length Rv1430 and its PE-PPE domain into pET-28a vector, expressed the proteins in E. coli and purified to homogeneity. The activity assays of both purified proteins were carried out using p-nitrophenyl esters of aliphatic carboxylic acids with varying chain length (C2-C16) to study the substrate specificity. To characterize the active site of the PE-PPE domain, we mutated the Ser199 to Ala. The activity of the protein in the presence of serine protease inhibitor- PMSF and the mutant protein were measured. Our results reveal that Rv1430 and its PE-PPE domain possess esterase activity and hydrolyse short to medium chain fatty acid esters with the highest specific activity for pNPC6 at 37°C, 38°C and pH 7.0, 8.0. The details of this work and the observed results are reported in this manuscript.
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