Chemical and immunological analysis of the complex structure of Escherichia coli alpha-hemolysin.

Escherichia coli alpha-hemolysin (AH) purified from culture supernatants by gel filtration and ion-exchange chromatography was heterogeneous in charge and size. A 107,000-dalton protein was identified as the product of the hlyA gene by its reactivity with anti-AH monoclonal antibodies. Proteolysis of the product of the hlyA gene occurred but was not required for transport of the protein through the cell wall. Active AH had a larger size and lower pI than analysis of the hlyA gene sequence would predict, thus suggesting that the hlyA protein is complexed with other bacterial products. Lipopolysaccharide was detected in purified hemolysin complex preparations and may be a major component of the complexes. These findings suggest several possible mechanisms for release of AH from the bacterial cell including release by outer membrane fragmentation. The existence of AH complexed with lipopolysaccharide may have important implications in understanding its toxicity.