The structure of Staphylococcus aureus alpha-toxin-induced ionic channel.
Abstract
Polyethylene glycols (PEG) with molecular weight less than or equal to 3000 were shown to effectively protect human erythrocytes from osmotic lysis induced by alpha-staphylotoxin (ST). PEG with MW less than 3000 do not change the conductivity of ion channels induced by ST in bilayer lipid membranes (BLM). Changing the bilayer from a pure phosphatidylcholine (PC) to a negatively charged phosphatidylserine (PS) film results in an asymmetry of the current-voltage characteristics. This is evidenced by the asymmetrical position of the ST-channel pore in bilayer membranes. The results obtained allow to conclude that the ST-channel is an interprotein pore filled with water (with an inner diameter of 2.5-3 nm and a length of approximately 10 nm). It is composed of six molecules of alpha-toxin from Staphylococcus aureus. The ST-channel incorporates into a membrane with only one mouth in contact with the polar lipid heads and the other one protruding 4.5-5 nm from the bilayer plane in water solution.