Further Study on the Two Pivotal Parts of Hlg2 for the Full Hemolytic Activity of Staphylococcal γ-Hemolysin

Abstract

  Staphylococcal γ-hemolysin consists of LukF of 34 kDa and Hlg2 (or HγII) of 32 kDa, which cooperatively lyse human and rabbit erythrocytes. Our previous data showed that the 5-residue segment K²³R²⁴L²⁵A²⁶I²⁷ of Hlg2 is pivotal for the hemolytic activity [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 γ-hemolysin activity by measuring the toxin activity of Hlg2 mutants in the presence of LukF. The data obtained showed that Arg²¹⁷ of Hlg2 is an additional pivotal amino acid residue besides the KRLAI segment for the full Hlg2-specific function in γ-hemolysin. We also report evidence that the Hlg2 mutants showing a low or null hemolytic activity 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 complex on the erythrocytes.