Biologically Active Arg-Gly-Asp Oligopeptides Assume a Type II β-Turn in Solution

Abstract

The sequence Arg-Gly-Asp (RGD) has been found to be the consensus sequence of matrix proteins for binding cell surface receptors (integrins). Studies with synthetic peptides containing the RGD sequence show that the biological activity of these oligopeptides is removed upon a conservative substitution of Glu for Asp in the RGD sequence. Two-dimensional NMR methods were used to investigate the secondary structures in aqueous solution for two such oligopeptides of differing biological activity. The sequence Tyr-Gly-Arg-Gly-Asp-Ser-Pro, which binds to selected integrins, is found to assume a type II (β-turn at both pH 4 and 7. In contrast, the sequence Tyr-Gly-Arg-Gly-Glu-Ser-Pro, which does no..