Conformational analysis of the Saccharomyces cerevisiae tridecapeptide mating pheromone by 13C,15N rotational-echo double resonance nuclear magnetic resonance spectroscopy.

The solid-state conformation of [Nle12]alpha-factor, the Saccharomyces cerevisiae tridecapeptide mating pheromone (WHWLQLKPGQPNleY), was investigated by 13C,15N rotational-echo double resonance (REDOR) nuclear magnetic resonance spectroscopy (NMR). Previous high-resolution NMR studies of [Nle12]alpha-factor in solution revealed a transient Type II beta-turn spanning residues 7-10 of the peptide. To investigate this region of [Nle12]alpha-factor in the solid state, a series of four selectively 13C,15N-enriched tridecapeptides were synthesized by solid-phase methods. Carbon-nitrogen distances between the labeled sites in lyophilized samples of [Nle12]alpha-factor were accurately measured by REDOR NMR. Experimentally determined distances were compared with those from calculated models for Type I and Type II beta-turns and for an extended chain. The measured distances indicate that, in a lyophilized powder, the central region of the [Nle12]alpha-factor is not in an extended conformation. The experimental data was most consistent with distances obtained from a distorted Type I beta-turn model.