Investigating Possible Interactions between Ionizable Residues in Model Transmembrane Peptides

Abstract

membrane and the atomic structure has been resolved by X-ray crystallography. The hydrophobic thickness of the protein observed in the structure 29.7A is considerably thinner than that predicted for the membrane 35.5A suggesting a hydrophobic mismatch. This hydrophobic mismatch is expected to aid protein-protein interactions and result in lipid sorting. Furthermore the surface of the protein has several cationic groups that could result in specific interactions with anionic lipid species. In order to investigate the local environment of Aquaporin Z in native E. coli membranes, and so understand the degree of lipid sorting and local protein-protein interactions, we have isolated Styrene-Maleic Acid Lipid Particles. These particles are believed to contain small portions of membrane isolated by the detergent action of the polymer. We have analysed particles isolated from E.coli membranes and containing Aquaporing Z for size, lipid and protein content. We have compared these experimental results to results obtained from coarse grained molecular dynamic simulations. These results are interpreted in terms of the interactions between the aquaporin and its environment.