A molecular pin to study the dynamics of beta-barrel formation in pore-forming toxins on erythrocytes: a sliding model.
gamma-Hemolysins are pore-forming toxins which develop from water-soluble monomers by combining two different 'albeit homologous' proteins. They form oligomeric pores in both cell and model membranes by undergoing a still poorly understood conformational rearrangement in the stem region. The stem is formed by three beta-strands, folded onto the core of the soluble protein and completely extended in the pore. We propose a new model to explain such a process. Seven double-cysteine mutants were developed by inserting one cysteine on the stretch that links the beta-hairpin to the core of the protein and another on different positions along the beta-strands. The membrane bound protein was blocked in a non-lytic state by S-S bond formation. Six mutants were oxidized as inactive intermediates, but became active after adding DTT. These results demonstrate that the stem extension can be temporarily frozen and that the beta-barrel formation occurs by beta-strand concerted step-by-step sliding.
Viero
G
G
FBK-CNR Institute of Biophysics, Unit at Trento, Via alla Cascata 56/C, 38100, Povo (Trento), Italy. viero@fbk.eu
Gropuzzo
A
A
Joubert
O
O
Keller
D
D
Prévost
G
G
Dalla Serra
M
M
D000818:Animals; D003545:Cysteine / Q000235:genetics; D004220:Disulfides / Q000378:metabolism; D004594:Electrophysiology; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D008567:Membranes, Artificial; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D011817:Rabbits; D013696:Temperature; D013997:Time Factors
D004220:Disulfides; D006460:Hemolysin Proteins; D008567:Membranes, Artificial; D050505:Mutant Proteins; D003545:Cysteine