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Helix-stabilizing Interaction Between Tyrosine and Leucine or Valine when the Spacing is i,i + 4

1994; Elsevier BV; Volume: 241; Issue: 5 Linguagem: Inglês

10.1006/jmbi.1994.1545

1089-8638

S. Padmanabhan, Robert L. Baldwin,

Protein Structure and Dynamics

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.