A type II beta-turn in a flexible peptide: proton assignment and conformational analysis of the alpha-factor from Saccharomyces cerevisiae in solution.

Abstract

AbstractTwo‐dimensional 1H‐nmr spectra of the α‐mating factor [in dimethyl sulfoxide‐d6 (DMSO) and in water] and several dodecapeptide analogues (in DMSO) were obtained. Homonuclear correlated spectroscopy resulted in the complete and unequivocal assignment of all backbone and side‐chain resonances of the peptides. The solution conformation of the pheromones was probed using two‐dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY) and rotating frame nuclear Overhauer effect spectroscopy (ROESY). The 2D NOE results, and results of complementary one‐dimensional experiments, suggest that a type II β‐turn is assumed by the central portion of active pheromones in both DMSO and water. Inactive analogues of the α‐factor do not exhibit this structural feature. Except for this one β‐turn, the nmr parameters for α‐factor are indicative of a conformationally flexible molecule in both solvents. This conclusion is in contrast to that of other researchers who have proposed a highly structured conformation of α‐factor in aqueous solution.