| Abstract
| - Attenuated total reflection Fourier transform infraredspectroscopy has been used to study thesecondary structure of anthrax lethal toxin proteins: protectiveantigen (PA) and lethal factor (LF), as afunction of pH in the absence and in the presence of phospholipidvesicles. We first characterized thebinding of LF and PA to the lipid membrane and demonstrated the strongpH dependence of the associationof PA and LF to the lipid bilayer as well as the effect of pHneutralization on this binding. Binding ofLF to the lipid membrane can be, at least partially, reversed when thepH is brought to neutral whereasin the same conditions PA binding is irreversible.Characterization of the conformational changesundergoneby PA and LF upon pH lowering, lipid binding, and, in the case of LF,reversal of binding was carriedout (i) by determining the secondary structure of the proteins and (ii)by evaluating their ability to undergoan hydrogen/deuterium exchange.
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