Interaction of native and partially folded conformations of alpha-lactalbumin with lipid bilayers: characterization of two membrane-bound states.

alpha-Lactalbumin (alphaLA) can adopt two different membrane-bound states depending on the physical properties of the lipid bilayer, namely adsorbed and inserted. The latter, but not the adsorbed state, is able to disrupt the permeability barrier of the bilayer. The structure of both states is strongly affected by the conformational properties of the alphaLA conformer considered: as protein flexibility increases the helical content of the membrane-bound conformation decreases, especially in the adsorbed form. Moreover, the adsorbed and the inserted states of those conformers containing 3 or 4 disulfides can interconvert in response to changes in the physical properties of the host membrane.