Antigenicity and N-terminal amino acid sequence of a 35 kDa porin-like protein of Listonella (Vibrio) anguillarum: comparison among different serotypes and other bacterial species.

Listonella (Vibrio) anguillarum, an important fish pathogen, is divided into 10 serotypes according to O-antigens present on the outer membrane. However, the biochemical and immunological properties of porin proteins have not been reported. In this study, the antigenicity and N-terminal amino acid sequence of the 35 kDa porin-like-major outer membrane protein (Omp35La) were compared among different serotypes of L. anguillarum as well as other bacteria. In Western blotting analysis, antisera against Omp35La from strains of J-O-1, -2 and -3 serotypes could detect Omp35La, but not other proteins, in most L. anguillarum strains and isolated of the genera Vibrio and Photobacterium. This antigenicity of Omp35La is unrelated to the serotype and is conserved in related organisms. An N-terminal sequence showed identification with OmpF and OmpC of Escherichia coli and Salmonella typhimurium. However, this similarity was lower when compared to other human pathogens. Thus it was concluded that Omp35La does not contribute to the serotypes of L. anguillarum, although the N-terminal structure is well conserved among different serotypes.