SECONDARY STRUCTURE INDUCTION IN AQUEOUS VS MEMBRANE-LIKE ENVIRONMENTS

The conformational propensity of the 20 naturally occurring amino acid s was determined in aqueous 3[N-morpholino]propane-sulfonic acid (MOPS ) buffer, protein interior-like [nonmicellar sodium dodecylsulfate (SD S)] and membrane-like environments (micellar SDS and lysophosphatidylg lycerol/lysophosphatidylcholine micelles) using a single ''guest'' pos ition in a polyalanine-based model host peptide (Ac-KYA(13)K-NH2). Thi s model system allows the intrinsic alpha-helical or beta-sheet propen sity of the amino acids to be determined without intra- and interchain side chain interactions. The overall environment dependence observed for the conformational propensity for the amino acids studied confirms the importance of determining propensity in lipidic environments to b etter elucidate the biological functions of proteins. The hydrophobic interactions between peptide side chains and lipids appeared to be the primary forces driving the conformational induction in lipidic enviro nments of the model peptides studied. Finally, when comparing the resu lts of these studies with those reported in the literature, the local environment was found to highly influence 65% of the 20 naturally occu rring amino acids. (C) 1997 John Wiley & Sons, Inc.