A proton N.M.R. study of the conformation of Trp-Gly-Ala-Glu in dimethyl sulfoxide and water

Abstract

Proton nuclear magnetic resonance parameters are reported for Trp-Gly-Ala-Glu, constituting residues 115-118 of bovine myelin basic protein, in dimethyl sulfoxide solution. The 3JNH,α vicinal coupling constants which were used to determine Φ torsional angles, together with the amide proton temperature coefficients, are consistent with a type I ,βturn conformation. Amide proton tempera- ture coefficients obtained for the peptide dissolved in H2O at pH 1.3, 4.6 and 6.5 indicate that the peptide does not adopt any highly preferred folded conformation in water. These findings lend support to previous reports of a reverse turn involving the Trp-Gly-Ala-Glu portion of the encephalitogenic nonapeptide Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys from bovine myelin basic protein.