title: Helix-stabilizing interaction between tyrosine and leucine or valine when the spacing is i, i + 4.
abstract: A helix-stabilizing interaction between tyrosine and leucine or valine has been found in alanine-based peptide helices when the spacing is i, i + 4. Control peptides have identical compositions but an i, i + 3 spacing. This is, to our knowledge, the first report of a helix-stabilizing interaction between two non-polar side-chains in an isolated helix. The results explain why, in an earlier study, leucine was found to have a helix propensity similar to that of alanine in an alanine-based peptide, whereas later work from another laboratory and our own has shown that alanine is markedly more helix-stabilizing than leucine in alanine-based peptides. The change in helix content resulting from the i, i + 4 Tyr-Leu interaction is comparable to the changes seen for other specific interactions between pairs of side-chains, such as ion-pair or Phe.His+ interactions.
authors.affiliation: Department of Biochemistry, Beckman Center, Stanford University Medical School, CA 94305-5307.
authors.forename: S
authors.initials: S
authors.lastname: Padmanabhan
authors.forename: R L
authors.initials: RL
authors.lastname: Baldwin
mesh_terms: D000595:Amino Acid Sequence; D006860:Hydrogen Bonding; D007700:Kinetics; D007930:Leucine / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D014443:Tyrosine / Q000737:chemistry*; D014633:Valine / Q000737:chemistry*
chemical_list: D010455:Peptides; D014443:Tyrosine; D007930:Leucine; D014633:Valine