Conformational study of the threonine-rich C-terminal pentapeptide of peptide T

The conformation of the synthetic pentapeptide Thr-Thr-Asn-Tyr-Thr, the C-terminal part of peptide T has been studied using 2D NMR experiments. The nuclear Overhauser effects (NOESY) and the low temperature coefficients for two particular NH chemical shifts allow the proposal for two distinct beta-turn arrangements. This conformation is not in accordance with recent reports but is consistent with observed beta-bends in two sequences of ribonuclease A. The semi-rigid conformation found in the pentapeptide in which the hydroxyl groups are exposed at the periphery of the molecule could be a crucial feature to explain the ability of peptide T to bind to a specific receptor and to correlate with the observed biological activity against HIV.