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The Energetics of Ion-Pair and Hydrogen-Bonding Interactions in a Helical Peptide

Scholtz, J. Martin and Qian, Hong and Robbins, Virginia H. and Baldwin, Robert L. (1993) The Energetics of Ion-Pair and Hydrogen-Bonding Interactions in a Helical Peptide. Biochemistry, 32 (37). pp. 9668-9676. ISSN 0006-2960.

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A single pair of Glu and Lys residues has been placed at four different spacings, and in both orientations, in an otherwise neutral alanineglutamine peptide helix, and the contribution to helix stability of the different Glu-Lys interactions has been measured. The contribution from the interaction of each charged side chain with the helix macrodipole has also been determined. A side-chain interaction between Gln and Glu, when the spacing is (i, i+4), has been detected and quantified. The interactions have been divided into contributions from hydrogen bonds (independent of the concentration of NaC1) and from electrostatic interactions (present in 10 mM NaCl, absent in 2.5 M NaCl). The major results are as follows: (1) The (i, i+3) and (i, i+4) Glu-Lys interactions are helix-stabilizing and are similar in strength to each other, regardless of the orientation of the side chains. (2) Hydrogen bonds provide the major contribution to these side-chain interactions, as shown by the following facts. First, the major part of the interaction observed in 10 mM NaCl, pH 7, is still present in 2.5 M NaCl. Second, the interaction found at pH 2 is equally as strong as that found in 2.5 M NaCl at pH 7. (3) The (i, i+4) Gln-Glu side-chain hydrogen bond is as strong as the hydrogen-bond component of the Glu-Lys interaction at both pH 2 and pH 7. The Gln-Glu interaction differs from the Glu-Lys interaction in being specific both for the orientation and the spacing of the residues. (4) No significant hydrogen-bonding interaction was found for the (i, i+1) or (i, i+2) Glu-Lys spacings, either at pH 2 or at pH 7, in 2.5 M NaCl. At 10 mM NaCl and pH 7, these spacings show a helix-destabilizing electrostatic interaction which probably results from stabilization of the coil conformation.

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Additional Information:© 1993 American Chemical Society. Published in print 21 September 1993. This work was supported by grants from the National Institutes of Health: GM 31475 (to R. L. B.) and GM 20195 (to John A. Schellman). J. M. S. is a Bank of America-Giannini Foundation Post-Doctoral Fellow.
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NIHGM 31475
NIHGM 20195
Bank of America-Giannini FoundationUNSPECIFIED
Issue or Number:37
Record Number:CaltechAUTHORS:20180207-135301595
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Official Citation:The energetics of ion-pair and hydrogen-bonding interactions in a helical peptide J. Martin Scholtz, Hong Qian, Virginia H. Robbins, and Robert L. Baldwin Biochemistry 1993 32 (37), 9668-9676 DOI: 10.1021/bi00088a019
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84726
Deposited By: Ruth Sustaita
Deposited On:08 Feb 2018 18:58
Last Modified:03 Oct 2019 19:21

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