TRANSCRIPTION OF THE VIBRIO-CHOLERAE HEMOLYSIN GENE, HLYA, AND CLONING OF A POSITIVE REGULATORY LOCUS, HLYU

Transcription of the Vibrio cholerae hlyA gene, which encodes a cytotoxic haemolysin, has been investigated. The hlyA transcript initiates 430 nucleotides (nt) upstream of the translational start site. hlyA-cat transcriptional fusion constructs were active in V. cholerae but not in Escherichia coli. An hlyA-cat fusion was used to select, from a V. cholerae 017 plasmid library, a clone that could activate the hlyA promoter in E. coli. This regulatory locus has been designated hlyU. hlyU appears to be distinct from the previously described hlyR locus.