Antiviral activity of hexapeptides derived from conserved regions of bacterial proteases against HCV NS3 protease.

The main cause of hepatitis C is hepatitis C virus or HCV and for the cure of hepatitis C, NS3/4A protease has been found an important and emerging target. A number of HCV NS3/4A protease inhibitors have been discovered which have shown subsequent reduction in reducing the viral load leading to this infection however they are still undergoing clinical trials for improvement. Bacterial proteases are of great pharmaceutical importance and have a key role in various biological processes and in life cycle of several pathogens. The current study was planned to explore hexapeptides derived from conserved regions of bacterial proteases for their potential in blocking the NS3 protease activity of HCV which would finally inhibit HCV multiplication. For this, a novel protease gene nprB was isolated from a thermophilic bacterium Streptomyces thermovulgaris and bioinformatics analyses were performed. PCR amplification and sequencing of nprB gene indicated an open reading frame of 178 aa (20191.18 Dalton).The peptide GGVHIN was the top ranked with minimum S-score of -17.21) followed by hexapeptides VDAHAN, GVGREA, GALNES and VHINSS with their S-scores of -14.73, -13.78, -10.72 and -10.70, respectively. A phylogram was also reconstructed to reveal evolutionary relationships of nprB with its various homologs. The provided data will serve as a background to further reveal pharmaceutical and biotechnological importance of this novel protease gene from S. thermovulgaris in future.

Isolation and characterization of nprB, a novel protease from Streptomyces thermovulgaris.

Bacterial proteases are of great pharmaceutical importance and have a key role in various biological processes and in life cycle of several pathogens. New technology used for rational protein engineering as well improved delivery options will expand the potential pharmaceutical applications of proteases. The catalytic proteases belong to metalloproteases (EC.3.4.24) that comprise thermo lysine. The metalloproteases and their homologs have many important biotechnological and therapeutic applications. In the present study, a novel protease gene nprB was isolated from a thermophilic bacterium Streptomyces thermovulgaris and bioinformatics analyses were performed. PCR amplification and sequencing of nprB gene indicated an open reading frame of 178 aa (20191.18 Dalton). Based on protein sequence homology as well as conserved motifs and PTF domain the protein is characterized as a thermo lysine-like protease and is a member of M4 family of metalloproteases. Different bioinformatics tools such as ProtParam, SOPMA, signalP4.1 and ProDom from the ExPAsy server were used for structural and functional analyses. A phylogram was also reconstructed to reveal evolutionary relationships of nprB with its various homologs. The provided data will serve as a background to further reveal pharmaceutical and biotechnological importance of this novel protease gene from S. thermovulgaris in future.

Cloning, Expression, and Characterization of a Metalloprotease from Thermophilic Bacterium Streptomyces thermovulgaris.

Proteases hydrolyze proteins and reduce them to smaller peptides or amino acids. Besides many biological processes, proteases play a crucial in different industrial applications. A 792 bp protease gene (nprB) from the thermophilic bacterium Streptomyces thermovulgaris was cloned and expressed in E. coli BL21 using pET 50b (+). Optimal recombinant protease expression was observed at 1 mM IPTG, 37 °C for 4 h. The resulting protease was observed in soluble form. The molecular mass estimated by SDS-PAGE and Western blot analysis of the protease (NprB) fused with His and Nus tag is ~70 KDa. The protease protein was purified by Ammonium sulfate precipitation and immobilized metal ion affinity chromatography. The optimum pH and temperature for protease activity using casein as substrate were 7.2 and 70 °C, respectively. The mature protease was active and retained 80% of its activity in a broad spectrum of pH 6-8 after 4 h of incubation. Also, the half-life of the protease at 70 °C was 4 h. EDTA (5 mM) completely inhibited the enzyme, proving the isolated protease was a metalloprotease. NprB activity was enhanced in the presence of Zn2+, Mn2+, Fe2+ and Ca2+, while Hg2+ and Ni2+ decreased its activity. Exposure to organic solvents did not affect the protease activity. The recombinant protease was stable in the presence of 10% organic solvents and surfactants. Further characterization showed that zinc-metalloprotease is promising for the detergent, laundry, leather, and pharmaceutical industries.

Structure based screening and molecular docking with dynamic simulation of natural secondary metabolites to target RNA-dependent RNA polymerase of five different retroviruses.

Viral diseases pose a serious global health threat due to their rapid transmission and widespread impact. The RNA-dependent RNA polymerase (RdRp) participates in the synthesis, transcription, and replication of viral RNA in host. The current study investigates the antiviral potential of secondary metabolites particularly those derived from bacteria, fungi, and plants to develop novel medicines. Using a virtual screening approach that combines molecular docking and molecular dynamics (MD) simulations, we aimed to discover compounds with strong interactions with RdRp of five different retroviruses. The top five compounds were selected for each viral RdRp based on their docking scores, binding patterns, molecular interactions, and drug-likeness properties. The molecular docking study uncovered several metabolites with antiviral activity against RdRp. For instance, cytochalasin Z8 had the lowest docking score of -8.9 (kcal/mol) against RdRp of SARS-CoV-2, aspulvinone D (-9.2 kcal/mol) against HIV-1, talaromyolide D (-9.9 kcal/mol) for hepatitis C, aspulvinone D (-9.9 kcal/mol) against Ebola and talaromyolide D also maintained the lowest docking score of -9.2 kcal/mol against RdRp enzyme of dengue virus. These compounds showed remarkable antiviral potential comparable to standard drug (remdesivir -7.4 kcal/mol) approved to target RdRp and possess no significant toxicity. The molecular dynamics simulation confirmed that the best selected ligands were firmly bound to their respective target proteins for a simulation time of 200 ns. The identified lead compounds possess distinctive pharmacological characteristics, making them potential candidates for repurposing as antiviral drugs against SARS-CoV-2. Further experimental evaluation and investigation are recommended to ascertain their efficacy and potential.