Transmembrane beta-barrel of staphylococcal alpha-toxin forms in sensitive but not in resistant cells.

摘要: Staphylococcal α-toxin is a 293-residue, single-chain polypeptide that spontaneously assembles into heptameric pore in target cell membranes. To identify the pore-forming domain, substitution mutants have been produced which single cysteine residues were introduced throughout toxin molecule. By attaching environmentally sensitive dye acrylodan to sulfhydryl groups, environment of individual amino acid side chains could be probed. In liposomes, 23-amino sequence (residues 118–140) was found move from polar nonpolar environment, indicating this forms walls pore. However, periodicity chain environmental polarity not detected liposomal system. present study, fluorimetric analyses extended physiological cells. With susceptible cells such as rabbit erythrocytes and human lymphocytes, 23 central acids 118–140 again insert membrane; contrast previous study with expected now detected. Thus, every other residue 126–140 entered striking display an amphipathic transmembrane β-barrel. contrast, granulocytes bind similar extent but heptamers forming on these failed their domain membrane. As consequence, nonfunctional assembled remained viable. The data resolve molecular organization living reveal resistant can prevent insertion functional bilayer.