An N-terminal region of LukF of staphylococcal leukocidin/gamma-hemolysin crucial for the biological activity of the toxin.

The two staphylococcal bi-component toxins, leukocidin and gamma-hemolysin share LukF [Kamio et al, FEBS Lett., 321, 15-18 (1993)]. This report identifies the pivotal amino acid residues in the N-terminal region of LukF for the leukocytolytic and hemolytic activities in the presence of LukS and HIg2, respectively, measuring the toxin activity of a series of LukF mutants with truncated N-terminals. The data obtained showed that the LukF mutant TF21, lacking 20 amino acid residues at the N-terminus of LukF, failed to have any hemolytic activity and had less 10% leukocytolytic activity than that of the intact LukF, while 16-residue truncations retained both toxin activities without loss. The LukF mutants lacking 18- through 19-residue segments from the N-terminus showed low toxin activity on both target cells. All mutants having no toxin activity were also not capable of binding to the human erythrocytes. It can thus be concluded that the 3-residue segment, L18Y19K20 of LukF is crucial for the biological activity of the toxin.