THE INTERACTION OF STAPHYLOCOCCUS-AUREUS BICOMPONENT GAMMA-HEMOLYSINSAND LEUCOCIDINS WITH CELLS AND LIPID-MEMBRANES

Staphylococcus aureus gamma-hemolysins (HlgA, HlgB and HlgC) and Panto n-Valentine leucocidins (LukS-PV and LukF-PV) are bi-component toxins forming a protein family with some relationship to alpha-toxin. Active toxins are couples formed by taking one protein from each of the two subfamilies of the S-components (LukS-PV, HlgA and HlgC) and the F-com ponents (LukF-PV and HlgB). We compared the mode of action of the six possible couples on leukocytes, red blood cells and model lipid membra nes. All couples were leucotoxic on human monocytes, whereas only four couples (HlgA+HlgB, HlgC+HlgB, LukS-PV+HlgB and HlgA+LukF-PV) were he molytic. Toxins HlgA+HlgB and HlgC+HlgB were also able to induce perme abilisation of model membranes by forming pores via oligomerisation. T he presence of membrane-bound aggregates, the smallest and most abunda nt of which had molecular weight and properties similar to that formed by alpha-toxin, was detected by SDS-PACE, By infrared spectroscopy in the attenuated total reflection configuration (FTIR-ATR), the seconda ry structure of both components and of the aggregate were determined t o be predominantly beta-sheet and turn with small variations among dif ferent toxins. Polarisation experiments indicated that the structure o f the membrane complex was compatible with the formation of a beta-bar rel oriented perpendicularly to the plane of the membrane, similar to that of porins. The couple LukS-PV+LukF-PV was leucotoxic, but not hem olytic. When challenged against model membranes it was able to bind to the lipid vesicles and to form the aggregate with the beta-barrel str ucture, but not to increase calcein permeability. Thus, the pore-formi ng effect correlated with the hemolytic, but not with the complete leu cotoxic activity of these toxins, suggesting that other mechanisms, li ke the interaction with endogenous cell proteins, might also play a ro le in their pathogenic action. (C) 1998 Elsevier Science B.V. All righ ts reserved.