Nucleotide sequences and comparison of the hemolysin determinants of Vibrio cholerae El Tor RV79(Hly+) and RV79(Hly-) and classical 569B(Hly-).

We determined the nucleotide sequences of the hemolysin structural gene, hlyA, of Vibrio cholerae El Tor biotype strains RV79(Hly+) and RV79(Hly-) and the hly determinant of the nonhemolytic classical biotype strain 569B(Hly-). The sequences of the hlyA gene from El Tor strains RV79(Hly+) and RV79(Hly-) have an identical 2,223-base open reading frame which is predicted to encode an 81,977-dalton precursor form of hemolysin. This value is in excellent agreement with the 84,000-Mr hemolysin described in the earlier report of Goldberg and Murphy (S. L. Goldberg and J. R. Murphy, J. Bacteriol. 162:35-41, 1985). In contrast, the sequence of the hly determinant of the classical 569B(Hly-) strain has an 11-base-pair deletion within the hlyA structural gene. In this instance the hly determinant is predicted to encode a 26,765-dalton precursor form of a truncated hemolysin. In each case, the regulatory region encoding the putative hlyA promoter and the predicted 25-amino-acid signal sequence are identical.