Assembly of the oligomeric membrane pore formed by Staphylococcal alpha-hemolysin examined by truncation mutagenesis.

摘要: The alpha-hemolysin (alpha HL) from Staphylococcus aureus causes the lysis of susceptible cells such as rabbit erythrocytes (rRBCs). Lysis is associated with formation a hexameric pore in plasma membrane. Here we show that truncation mutants alpha HL missing 2 to 22 N-terminal amino acids form oligomers on surfaces rRBCs but fail lyse cells. By contrast, 3 or 5 at C terminus are very inefficient oligomerization do rRBCs, albeit extremely slowly. C-terminal mutants, retarded monomers cell surface, undergo conformational change which protease-sensitive loop located near midpoint polypeptide chain becomes occluded. Judged by this criterion, polypeptides truncated N terminus, frozen nonlytic oligomers, similar conformation. A second proteolytic site inaccessible lytic formed wild-type polypeptide, supporting idea occurs upon formation. These findings suggest pathway for assembly first binds target monomer, converted oligomeric intermediate before pore. In keeping model, an mutant blocks slow induced mutant, presumably diverting weakly subunits into inactive oligomers.