Comparison of the haemolysin secretion protein HlyB from Proteus vulgaris and Escherichia coli; site-directed mutagenesis causing impairment of export function.

The hlyB secretion genes of Proteus vulgaris and Escherichia coli showed 81% nucleotide homology and similar E. coli-atypical codon usage. The deduced protein sequences differed in 54 of 707 residues and shared a previously unreported sequence which corresponds to the ATP-binding motif characteristic of protein kinases. The motif was also conserved in the HlyB of Morganella morganii. Of 4 oligonucleotide-directed substitutions introduced into the putative E. coli HlyB motif, 2 non-conservative changes caused radical reductions in the export of active haemolysin protein.