FURTHER STUDY ON THE 2 PIVOTAL PARTS OF HLG2 FOR THE FULL HEMOLYTIC-ACTIVITY OF STAPHYLOCOCCAL GAMMA-HEMOLYSIN

Staphylococcal gamma-hemolysin consists of LukF of 34 kDa and Hlg2 (or H gamma II) of 32 kDa, which cooperatively lyse human and rabbit eryt hrocytes. Our previous data showed that the 5-residue segment K(23)R(2 4)L(25)A(26)I(27) Of Hlg2 is pivotal for the hemolytic activity [Nariy a, H. and Kamio, Y., Biosci. Biotechnol. Biochem., 59, 1603-1604 (1997 )]. Here, we identify an additional amino acid residue in Hlg2 necessa ry for the full gamma-hemolysin activity by measuring the toxin activi ty of Hlg2 mutants in the presence of LukF. The data obtained showed t hat Arg(217) of Hlg2 is an additional pivotal amino acid residue besid es the KRLAI segment for the full Hlg2-specific function in gamma-hemo lysin. We also report evidence that the Hlg2 mutants showing a low or null hemolytic activity in the presence of LukF towards human erythroc ytes had low or no binding activity to the cells, resulting in failure of formation of the ring-shaped pore-forming complex on the erythrocy tes.