Abstract

Outer membrane protein U (OmpU), an adhesion protein of Vibrio mimicus, is a good antigen, but its epitopes are still unclear. In order to locate the epitopes of OmpU protein, epitope prediction was performed using the amino acid sequence of OmpU protein of V. mimicus HX4 strain that was isolated from the diseased crass carp in Anhui province of China. The secondary structure, flexible regions, hydrophilicity, surface accessibility and antigenic index of the protein were analyzed using the DNAStar Protean program, and seven potential epitopes were screened. To verify the prediction, the potential epitope peptides were artificially synthesized and detected by peptide-enzyme linked immunosorbent assay (ELISA). The results show that the potential epitope peptides at amino acid positions 25 to 33, 90 to 98, 117 to 126, 173 to 180, 183 to 195, 211 to 218 and 239 to 250 were indeed immunodominant linear B-cell epitopes of the OmpU protein. Among them, the epitopes at amino acid positions 25 to 33, 90 to 98 and 239 to 250 were entirely exposed on the surface of the 3D structure model of OmpU protein, and they had a stronger immunoreactivity than others that were partially embedded inside the protein molecule.

Key words: Vibrio mimicus, outer membrane protein U (ompU), linear B-cell epitope, localization, enzyme-linked immunosorbent assay.

Abbreviation

PCR, Polymerase chain reaction; ELISA, enzyme linked immunosorbent assay; OmpU, outer membrane protein U; IPTG, isopropyl-β-D-thiogalactopyranoside; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; MBP, maltose binding protein; OPD, o-phenylenediamine.