Solid State and Solution Conformations of a Helical Peptide with a Central Gly-Gly Segment

Karle, Isabella L and Banerjee, Arindam and Bhattacharjya, Surajit and Balaram, P (1996) Solid State and Solution Conformations of a Helical Peptide with a Central Gly-Gly Segment. In: Biopolymers, 38 (4). pp. 515-526.

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Abstract

The influence of amino acids with contrasting con formational tendencies on the stereochemistry of oligopeptides has been investigated using an octapeptide Boc-Leu-Aib- Val-Gly-Gly-Leu-Aih-Val-OMe, which contains two helix-promoting Aib residues and a central helix-destabilizing Gly-Gly segment. Single crystal x-ray diffraction studies reveal that a 310-helix is formed up to the penultimate Aib residue, at which point there is a helix reversal in the backbone, reminiscent of a C-terminal 6 - 1 hydrogen bond. The curious feature in the crystal is the solvation of the possible 6 - 1 bond by a CH30H molecule, where the OH is inserted between O(3) and N(8) and participates in hydrogen bonds with both. The cell parameters are as follows: space group P212121, a = 10.649 (4) Å, b = 15.694(5) Å, c = 30.181(8) Å, R = 6.7% for 3427 data ([Fo] > 3aF) observed to 0.9 Å. Nuclear magnetic resonance studies in CDC13 using NHgroup solvent accessibility and nuclear Overhauser effects as probes are consistent with a 310-helical conformation. In contrast, in (CD3)2S0, unfolding of the central segment results in a multiple beta-turn structure, with beta-turn conformations populated at residues 1-2, 3-4, and 6-7. CD studies in methanol-2,2,2-trifluoroethanol (TFE) mixtures also provide evidence for a solvent-dependent structural transition. Helical conformations are populated in TFE, while type II beta-turn structures are favored in methanol.

Item Type:	Journal Article
Publication:	Biopolymers
Publisher:	John Wiley & Sons, Inc
Additional Information:	Copyright for this article belongs to John Wiley & Sons, Inc.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	06 Nov 2004
Last Modified:	19 Sep 2010 04:17
URI:	http://eprints.iisc.ac.in/id/eprint/2267

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