ABSTRACT
Three-dimensional models of the chimeric S. typhi OmpC protein carrying an epitope from rotavirus VP4 capsid protein on either of two exposed loops (fourth and sixth) were constructed separately, using computer-aided homology modelling. The theoretical model of S. typhi OmpC was used as a template. The monomers were initially energy minimized. The trimers were generated for both the chimeric S. typhi OmpC proteins and the structures were optimized after several cycles of minimization. The surface accessibility calculations for the resulting models show that epitope recognition should be more effective in the fourth loop than in the sixth loop, in accordance with the experimental results on the immunogenic nature of the rotaviral epitope inserted into the two putative loops of S. typhi OmpC.
Subject(s)
Amino Acid Sequence , Antigen Presentation/physiology , Bacterial Proteins/chemistry , Epitopes , Models, Molecular , Molecular Sequence Data , Porins/chemistry , Protein Conformation , Salmonella typhi/immunologyABSTRACT
The possible B-cell epitopes of the outer membrane porin OmpC of Salmonella typhi have been identified, using the primary structure of the protein, by means of multiple sequence alignment and the known molecular structure of two other porins. From the analysis, 8 regions were identified as immunodominant and these were ranked based on antigenic index and the ratio of the number of nonconserved residues to the fragment length. Model building of the top two ranked regions show the tendency to form loop structures supporting the possibility of these being candidate epitopes.