Energetic contribution of solvent-exposed ion pairs to alpha-helix structure

Pingchiang C. Lyu, Paul J. Gans, Neville R. Kallenbach

Research output: Contribution to journalArticle

Abstract

Understanding the role of amino acid side-chain interactions in forming secondary structure in proteins is useful for deciphering how proteins fold and for predicting folded structures of proteins from their sequence. Analysis of the secondary structure as a function of pH in two designed synthetic peptides with identical composition but different sequences, affords a quantitative estimate of the free energy contribution of a single ion pair to the stability of an isolated α-helix. One peptide contains repeated blocks of Glu4Lys4. The second has repeated blocks of Glu2Lys2. The former contains significant helical structure at neutral pH while the latter has none, based on ultraviolet light circular dichroism measurements and 1H nuclear magnetic resonance spectroscopy. The difference is attributed to formation of helix-stabilizing salt-bridges between Glu- and Lys+ spaced at i, i + 4 intervals in the former peptide. The free energy of formation of a single Glu--Lys+ salt-bridge can be evaluated by using a statistical model of the helix-coil transition that explicitly includes salt-bridges: the result is -0.50(±0.05) kcal/mol at 4 °C and neutral pH in 10 mm salt, in agreement with a value derived for a single salt-bridge in a helix on the surface of a globular protein.

Original languageEnglish (US)
Pages (from-to)343-350
Number of pages8
JournalJournal of Molecular Biology
Volume223
Issue number1
DOIs
StatePublished - Jan 5 1992

Fingerprint

Salts
Ions
Peptides
Secondary Protein Structure
Proteins
Statistical Models
Ultraviolet Rays
Circular Dichroism
Magnetic Resonance Spectroscopy
alpha-Helical Protein Conformation
Amino Acids

Keywords

  • helix-coil transition
  • model peptides
  • protein folding
  • salt-bridges
  • α-helices

ASJC Scopus subject areas

  • Virology

Cite this

Energetic contribution of solvent-exposed ion pairs to alpha-helix structure. / Lyu, Pingchiang C.; Gans, Paul J.; Kallenbach, Neville R.

In: Journal of Molecular Biology, Vol. 223, No. 1, 05.01.1992, p. 343-350.

Research output: Contribution to journalArticle

Lyu, Pingchiang C. ; Gans, Paul J. ; Kallenbach, Neville R. / Energetic contribution of solvent-exposed ion pairs to alpha-helix structure. In: Journal of Molecular Biology. 1992 ; Vol. 223, No. 1. pp. 343-350.
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