INDUCTION OF HEMOLYTIC-ACTIVITY IN ESCHERICHIA-COLI BY THE SLYA GENE-PRODUCT

The Salmonella typhimurium protein SlyA(ST), originally described as a cytolysin, shows sequence similarities to several known bacterial reg ulatory proteins. A homologue to the slyA(ST) gene has been localised to min 37 of the Eschericia coli K-12 chromosome and has been designat ed slyA(EC). When introduced in trans on a plasmid, the slyA(EC) gene conferred a haemolytic phenotype on wild-type but not clyA-knockout st rains of E. coli K-12. The clyA gene encodes a novel haemolysin that i s not expressed by wild-type E. coil under tested laboratory condition s. Western and Northern blot analyses, and DNA-band-shift assays suppo rt a model whereby the SlyA(EC) protein activates clyA expression by b inding to the clyA promoter region, thereby supporting the sequence si milarity data in suggesting that SlyA(ST) is a haemolysin activator ra ther than being a haemolysin per se.