Helix capping propensities in peptides parallel those in proteins

Avijit Chakrabartty, Andrew J. Doig, Robert L. Baldwin

    Research output: Contribution to journalArticlepeer-review


    Helix content of peptides with various uncharged nonaromatic amino acids at either the N-terminal or C-terminal position has been determined. The choice of N-terminal amino acid has a major effect on helix stability: asparagine is the best, glycine is very good, and glutamine is the worst helix-stabilizing amino acid at this position. The rank order of helix stabilization parallels the frequencies of these amino acids at the N-terminal boundary (N-cap) position of helices in proteins found by Richardson and Richardson [Richardson, J. S. & Richardson, D. C. (1988) Science 240, 1648-1652], and the N-terminal amino acid in a peptide composed of helix-forming amino acids may be considered as the N-cap residue. The choice of C-terminal amino acid has only a minor effect on helix stability. N-capping interactions may be responsible for the asymmetric distribution of helix content within a given peptide found by various workers. An acetyl group on the N-terminal α-amino function cancels the N-cap effect and the acetyl group is equivalent to N-terminal asparagine in an unacetylated peptide. Our results demonstrate a close relationship between the mechanisms of α-helix formation in peptides and in proteins.
    Original languageEnglish
    Pages (from-to)11332-11336
    Number of pages4
    JournalProceedings of the National Academy of Sciences of the United States of America
    Issue number23
    Publication statusPublished - 1 Dec 1993


    • α-helix
    • Helix stability
    • N-cap and C-cap residues
    • Protein folding


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