Further Study on the Two Pivotal of Staphyloceccal 7-Hemolysin Parts ofHlg 2 for the Full Hemolytic Activity

Staphylecoccal 7-hemolysin consists of LukF of 34 kDa and Hlg2 (or H7II) of 32 kDa, which cooperative}y lyse human and rabbit erythrocytes. Our preyious data showed that the 5-residue segment K23RML25AasI27 of Hlg2 is piyotal for the hemolytic actiyity [Nariya, H. and Kamio, Y., Biosci. Biotechnol. Biochem., 59, 1603-1604 (1997)]. Here, we identify an additional amino acid residue in Hlg2 necessary for the full 7-hemelysin actiyity by measuring the toxin actiyity of Hlg2 mutants in the presence of LukF. The data obtained showed that Arg2" of Hlg2 is an additional pivotal amino acid residue besides the KRLAI segment for the full Hlg2-specific function in 7-hemolysin. We also report evidence that the Hlg2 mutants showi"g a low or null hemolytic actiyity in the presence of LukF towards human erythrocytes had low or no binding activity to the cells, resulting in failure of formation of the ring-shaped pore-forming comp}ex on the erythrocytes.