Comparative analysis of adhesion virulence protein FadA from gut-associated bacteria of colorectal cancer patients (F. nucleatum) and healthy individuals (E. cloacae).

Background: Colorectal cancer (CRC) is a gastrointestinal disease linked with GIT microbial dysbiosis. The present study has targeted the comparative analysis of virulent factor FadA from gut-associated bacteria of CRC patients (F. nucleatum) and healthy individuals (E. cloacae). Methods: For this purpose, FadA protein sequences of fifteen strains of F. nucleatum and four strains of E. cloacae, were retrieved from the UniProt database. These sequences were analysed through VirulentPred, PSLpred, ProtParam, PFP-FunDSeqE, PROTEUS Structure Prediction Server, SWISS-MODEL, SAVES validation server, MEME suite 5.5.0, CAVER Web tool, Webserver VaxinPAD, HPEPDOCK and HDOCK servers. Results: FadA protein from F. nucleatum was found to exhibit significant differences as compared to E. nucleatum i.e. it exhibited helical configuration, cytoplasmic, periplasmic, outer-membrane and extracellular localisation, 2D structure comprising of 70-96% helix, 0% beta-sheet, 4-30% coils and 17-20 signal peptide residues, hydrophilicity, strongly acidic character and smaller number of antigenic epitopes. In contrast, FadA protein from E. nucleatum was found to have globular 3D configuration, cytoplasmic localisation, 2D structure (30-56% helix, 12-21% beta-sheet, 33-50% coils and 43 signal peptide residues), highly hydrophobic, slightly acidic and more number of antigenic epitopes. Docking analyses of virulent factors revealed their high binding affinities with previously reported inhibitory peptide and FAD-approved drug COX2. Conclusion: The wide range of differences not only provided us the reason for the role of FadA protein as a virulent factor in F. nucleatum but also might help us in designing virulent FadA protein inhibiting strategies including peptide-based vaccine adjuvants and drugs designing, modification of tunnels and catalytic pockets to reduce substrate binding and FAD approved drugs selection. Inhibition of this virulent factor in CRC patients' gut bacteria might result in oncogenesis regression and reduced death rate.