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Cyclic Peptide Disulfides Consecutive \beta -Turn Conformation of a Synthetic Model Peptide Corresponding to the Active Site of Thioredoxin

Ravi, A and Balaram, P (1983) Cyclic Peptide Disulfides Consecutive \beta -Turn Conformation of a Synthetic Model Peptide Corresponding to the Active Site of Thioredoxin. In: Biochimica et Biophysica Acta, Protein Structure and Molecular Enzymology, 745 (3). pp. 301-309.

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Abstract

A synthetic model peptide, $Boc-Cys_\mid _S-Gly-Pro-Cys_\mid _S-NHMe$, which mimics the active-site disulfide loop of thioredoxin has been prepared. 270 MHz $^1H$-NMR studies establish that Cys-4 and methylamide NH groups are solvent-shielded, using hydrogen-deuterium exchange, solvent and temperature dependence of chemical shifts and nitroxide radical-induced broadening as diagnostic criteria. Infrared measurements provide supporting evidence for intramolecularly hydrogen-bonded conformations. The related peptide in which Gly-2 is replaced by \alpha -aminoisobutyric acid has been shown to adopt a similar backbone conformation based on NMR and CD data. Based on the known stereochemical preferences of \alpha -aminoisobutyric acid residues, a consecutive \beta -turn conformation involving two intramolecular 4 \rightarrow 1 hydrogen bonds is proposed for both disulfides. Vicinal coupling constants and CD data are discussed with reference to the side-chain conformation of the cysteine residues. Large structural differences have been established between the thioredoxin active-site model disulfide and its acyclic precursor.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier Science B.V.
Keywords: Thioredoxin;Cyclic peptide disulfide;Model peptide;β-turn conformation;Active site.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 03 Apr 2008
Last Modified: 19 Sep 2010 04:44
URI: http://eprints.iisc.ernet.in/id/eprint/13647

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