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 ³J_NH,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.