Existence of a new protein component with the same function as the LukF component of leukocidin or γ-hemolysin and its gene in Staphylococcus aureus P83

Staphylococcal toxins, leukocidin and γ-hemolysin, consist of two protein components, i.e. LukF and LukS for leukocodin and HγI and HγII for γ-hemolysin. From a culture fluid of Staphylococcus aureus strain P83, a new protein component of leukocidin or γ-hemolysin which was designated as LukM was isolated. This component showed the same biological activity as that of LukF component for leukocidin or HγI component of γ-hemolysin in combination with LukS or HγII. However, the LukM component cross-reacted with the anti-LukS antibodies but not with the anti-LukF antibodies. On the basis of chemical analysis of the LukM component and the cloning and nucleotide sequencing of the lukM gene of S. aureus P83, we have demonstrated that LukM is an entirely new protein component of leukocidin or γ-hemolysin. The deduced amino acid sequence of LukM from the lukM gene showed 66.7% and 67% indentity to that of LukS and Hγll, respectively. However, the amino acid sequence of LukM and LukF showed only 29% homology.