Caveolin-1 binding motif of α-hemolysin: its role in stability and pore formation

Abstract We have identified a nine amino sequence in α-hemolysin (α-HL) of Staphylococcus aureus, which binds Caveolin-1. Surface plasmon resonance studies clearly show a concentration dependent interaction of α-HL with the scaffolding domain of Caveolin-1. Mutants of α-HL, devoid of Caveolin-1 recognition motif, exhibit an α-HL like proteinase K digestion profile but the resultant ‘half-like’ domains are highly susceptible to further proteolysis. They also had the same intrinsic fluorescence emission maxima as the native α-HL indicating normal folding. However, these mutants bind 1-anilino-8-naphthalene sulfonic acid probably due to exposure of their hydrophobic core. Moreover, these mutants are non-lytic and do not undergo conformational changes on rabbit RBC membrane surface. Purified Caveolin-1 blocks the hemolysis of RBCs by α-HL. Our studies indicate that the Caveolin-1 binding motif of α-HL provides stability and shields the hydrophobic core of α-HL. The motif also acts as trigger point for initiation of conformational changes.

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