Stabilization of unusual structures in peptides using alpha,beta-dehydrophenylalanine: Crystal and solution structures of Boc-Pro-Delta Phe-Val-Delta Phe-Ala-OMe and Boc-Pro-Delta Phe-Gly-Delta Phe-Ala-OMe

Mathur, P and Ramagopal, UA and Ramakumar, Suryanarayanarao and Jagannathan, NR and Chauhan, VS (2006) Stabilization of unusual structures in peptides using alpha,beta-dehydrophenylalanine: Crystal and solution structures of Boc-Pro-Delta Phe-Val-Delta Phe-Ala-OMe and Boc-Pro-Delta Phe-Gly-Delta Phe-Ala-OMe. In: Biopolymers, 84 (3). pp. 298-309.

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Abstract

The structures of two dehydropentapeptides, Boc-Pro-Delta Phe-Val-Delta Phe-Ala-OMe (I) and Boc-Pro-Delta Phe-Gly-Delta Phe-Ala-OMe (II) (Boc: t-butoxycarbonyl), have been determined by nuclear magnentic resonance (NMR), circular dichroism (CD), and X-ray, crystallographic studies. The peptide I assumes a S-shaped flat beta-bend structure, characterized by two partially overlapping type II beta-bends and absence of a second 1 <- 4 (N4-H center dot center dot center dot O1') intramolecular hydrogen bond. This is in contrast to the generally observed 3(10)-helical conformation in peptides with Delta Phe at alternate positions. This report describes the novel conformation assumed by peptide I and compares it with that of the conserved tip of the V3 loop of the HIV-1 envelope glycoprotein gp120 (sequence, G:P319 to F:P324, PDB code IACY). The tip of the V3 loop also assumes a S-shaped conformation with Arg:P322, making an intramolecular side-chain-backbone interaction with the carbonyl oxygen of Gly:P319. Interestingly, in peptide I, C(gamma)HVal(3) makes a similar side-chain-backbone C-H center dot center dot center dot O hydrogen bond with the carbonyl oxygen of the Boc group. The observed overall similarity indicates the possible use of the peptide as a viral antagonist or synthetic antigen. Peptide 11 adopts a unique turn followed by a 3(10)-helix. Both peptides I and II are classical examples of stabilization of unusual structures in oligopeptides.

Item Type:	Journal Article
Publication:	Biopolymers
Publisher:	Wiley Periodicals Inc
Additional Information:	Copyright of this article belongs to Wiley Periodicals Inc.
Keywords:	dehydropentapeptides; nuclear magnetic resonance; circular dichroism; X-ray crystallography; beta-bend; hydrogen bond; 3(10)-helical conformation; oligopeptides.
Department/Centre:	Division of Information Sciences (Doesn't exist now) > BioInformatics Centre Division of Physical & Mathematical Sciences > Physics
Date Deposited:	28 Sep 2010 10:07
Last Modified:	28 Sep 2010 10:07
URI:	http://eprints.iisc.ac.in/id/eprint/31653

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