Bioinformatics Approaches for Functional and Structural Annotation and Molecular Docking Study of a Hypothetical...

Staphylococcus aureus is a common Gram-positive bacterium that colonizes the skin and mucous membranes of humans. It is a major etiological agent of nosocomial infections and a persistent source of contamination in food and hospitals. The complete sequencing of the S. aureus genome has been accomplished, yet numerous hypothetical proteins encoded within it remain functionally uncharacterized. For this study, we performed a comprehensive functional and structural analysis of a hypothetical protein (accession number OHS92176.1) from the S. aureus HMSC77A05 strain using bioinformatics approaches. Physicochemical investigations showed that the protein is stable, soluble, and cytosolic. Functional annotation using NCBI Conserved Domain Search, InterProScan, and Pfam databases identified that the protein is a member of the YqeG family of HAD IIIA-type phosphatases within the haloacid dehalogenase (HAD) superfamily. Multiple sequence alignment showed that many strains of S. aureus are very similar in their evolution, indicating that they are likely important for their function. Both PSIPRED and SOPMA consistently predicted that α-helical elements are the most common part of the secondary structure of proteins. A three-dimensional model was constructed using SWISS-MODEL and template A0A2C6WKT6.1.A, exhibiting 71.43% sequence identity with the target protein. The model quality underwent validation using ERRAT, Verify3D, QMEAN, and PROCHECK analyses, all of which affirmed its structural reliability and stereochemical accuracy. STRING's study of protein-protein interactions found associations with enzymes involved in ribosomes, amino acid biosynthesis, and nucleotide catabolism. It was also discovered that the active site has four putative catalytic pockets. Molecular docking simulations were subsequently conducted using six phytocompound ligands-quercetin, kaempferol, naringenin, apigenin, catechin, and curcumin-all of which demonstrated favorable binding affinities. Notably, kaempferol exhibited the highest binding affinity (ΔG = -8.3 kcal/mol). These findings indicate that this previously uncharacterized hypothetical protein may serve as a promising therapeutic target for an antibacterial agent against S. aureus. The comprehensive computational analyses provide a robust foundation for subsequent experimental validation and structure-based drug development.