The N-Terminal Amino-Latch Region Of Hlg2 Component Of Staphylococcal Bi-Component Gamma-Haemolysin Is Dispensable For Prestem Release To Form Beta-Barrel Pores

The contribution of N-terminal regions of staphylococcal bi-component gamma-haemolysin toxin components to haemolytic activity towards human erythrocyte cells was investigated in this study. A deletion construct of N-terminal amino acids 1-10 of Hlg2 (Hlg2 Delta N10), which is the S-component protein of gamma-haemolysin, had little effect on its haemolytic activity, whereas N-terminal 1-11 amino acid deletion (Hlg2 Delta N11) significantly delayed haemolysis. Moreover, a deletion of N-terminal amino acids 1-17 of LukF, which is the F-component protein of gamma-haemolysin, increased its haemolytic activity in combination with either the wild-type or Hlg2 Delta N10. Unlike the N-terminal amino-latch region of staphylococcal alpha-haemolysin, which is a single component beta-barrel pore-forming toxin, the N-terminal regions present in gamma-haemolysin components are dispensable for the haemolytic activity of the bi-component toxin. These results strengthen our recent proposal that staphylococcal bi-component gamma-haemolysin toxin uses an N-terminal amino-latch independent molecular switch for prestem release during the formation of beta-barrel pores.