How proteins adapt to a membrane-water interface

Membrane proteins present a hydrophobic surface to the surrounding lipid, w hereas portions protruding into the aqueous milieu expose a polar surface. But how have proteins evolved to deal with the complex environment at the m embrane-water interface? Some insights have been provided by high-resolutio n structures of membrane proteins, and recent studies of the role of indivi dual amino acids in mediating protein-lipid contacts have shed further ligh t on this issue. It now appears clear that the polar-aromatic residues Trp and Tyr have a specific affinity for a region near the lipid carbonyls, whe reas positively charged residues extend into the lipid phosphate region.