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Scientific article
English

The staphylococcal alpha-toxin pore has a flexible conformation

Published inBiochemistry, vol. 38, no. 14, p. 4296-4302
Publication date1999
Abstract

The alpha-toxin from Staphylococcus aureus undergoes several conformational changes from the time it is released from the bacterium to the moment it forms a channel in the plasma membrane of its target cell. It is initially a soluble monomer, which undergoes membrane binding and oligomerization into a heptameric ring and finally inserts into the lipid bilayer to form a pore. Here we have analyzed the stability of different forms of the alpha-toxin (monomer as well as heptamers in solution, bound to the membrane and membrane-inserted) by differential scanning calorimetry and limited proteolysis. Data presented here show that, in contrast to both the membrane-bound prepore complex and the monomer in solution, the membrane-inserted alpha-toxin channel does not undergo cooperative unfolding and is highly susceptible to proteases. These observations suggest that the channel has a looser conformation. Interestingly, resistance to proteases could be recovered upon solubilization of the channel, indicating that the loss of rigid tertiary packing only occurred upon membrane insertion. Far-UV CD data, however, suggest that the transmembrane beta-barrel must be stably folded and that therefore only the Cap and Rim domains of the channel are loosely packed. All together, our data show that the alpha-toxin channel is not a rigid complex within the membrane but adopts a rather flexible conformation.

Citation (ISO format)
VECSEY SEMJEN, Beatrix et al. The staphylococcal alpha-toxin pore has a flexible conformation. In: Biochemistry, 1999, vol. 38, n° 14, p. 4296–4302. doi: 10.1021/bi982472k
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ISSN of the journal0006-2960
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