Structure of functional Staphylococcus aureus alpha-hemolysin channels in tethered bilayer lipid membranes

Abstract

We demonstrate a method for simultaneous structure and function determination of integral membrane proteins. Electrical impedance spectroscopy shows that Staphylococcus aureus a-hemolysin channels in membranes tethered to gold have the same properties as those formed in free-standing bilayer lipid membranes. Neutron reflectometry provides high-reso- lution structural information on the interaction between the channel and the disordered membrane, validating predictions based on the channel,s x-ray crystal structure. The robust nature of the membrane enabled the precise localization of the protein within 1.1 Å. The channel's extramembranous cap domain affects the lipid headgroup region and the alkyl chains in the outer membrane leaflet and significantly dehydrates the headgroups. The results suggest that this technique could be used to elucidate molecular details of the association of other proteins with membranes and may provide structural information on domain organization and stimuli-responsive reorganization for transmembrane proteins in membrane mimics.