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-hemol ysin share LnkF [Kamio et al, FEBS Lett., 321, 15-18 (1993)]. This rep ort identifies the pivotal amino acid residues in the N-terminal regio n of LukF for the leukocytolytic and hemolytic activities in the prese nce of LukS and Hlg2, respectively, measuring the toxin activiy of a s eries of LukF mutants with truncated N-terminals. The data obtained sh owed 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 10-re sidue truncations retained both toxin activities without loss. The Luk F 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 erythrocy tes. It can thus be concluded that the 3-residue segment, (LYK20)-Y-18 -K-19 Of LukF is crucial for the biological activity of the toxin.