Purification of the 25-kDa Vibrio cholerae major outer-membrane protein and the molecular cloning of its gene: ompV.

The 25-kDa peptidoglycan-associated outer-membrane protein and most likely porin of Vibrio cholerae is a major immunogenic species. It has been purified by ion-exchange elution on hydroxyapatite followed by gel filtration on Bio-Gel P150 both in the presence of sodium dodecyl sulfate. This protein, of greater than 90% purity as judged by Western blotting, has been used to raise antibodies in rabbits. The antisera were then used to screen V. cholerae gene banks, constructed in Escherichia coli K12, and this has enabled us to isolate several colonies harbouring the cloned gene. The plasmids in these colonies have been designated pPM451, pPM455 and pPM472. These plasmids have a 5.3 X 10(3)-base BamHI fragment of V. cholerae DNA in common. Restriction endonuclease mapping of these plasmids has been performed and the protein identified both by Western blot analysis and in E. coli K12 minicells. The protein is not efficiently expressed in E. coli K12. It is proposed to use the name ompV to describe the structural gene, present in the cloned DNA, for this V. cholerae outer membrane protein.