title: Nuclear-magnetic-resonance studies on the conformations of tridecapeptide alpha-mating factor from yeast Saccharomyces cerevisiae and analog peptides in aqueous solution. Conformation-activity relationship.
abstract: The conformation of tridecapeptide alpha-mating factor from yeast Saccharomyces cerevisiae in aqueous solution was analyzed, in comparison with those of active analog and inactive analog peptides. 270-MHz 1H-NMR spectra of these peptides were observed and the spectral patterns of main-chain N-H proton resonances were classified into three groups. alpha-mating factor and Trp1-bearing active peptides belong to the group A1, active des-Trp1-peptides belong to the group A2 while the peptides of group B are inactive. The main-chain N-H proton resonances of the groups A1 and A2 and side-chain N-H proton resonances were all assigned to individual residues. The 13C-NMR analysis of alpha-mating factor indicates that the Lys7-Pro8 and Gln10-Pro11 peptide bonds exclusively take the trans form. From the temperature and pH dependences of chemical shifts and Gd(III)-induced relaxation enhancements of amide proton resonances, alpha-mating factor is found to take partly a folded conformation in aqueous solution, with an alpha-helical form in the N-terminal domain and two beta-turn forms in the central and C-terminal domain. The pH dependence of fluorescence intensity indicates that, in this folded conformation, the C-terminal carboxylate group lies close to the N-terminal domain. The presence of the folded form in the N-terminal domain and the beta-turn form in the central domain correlates with the biological activity of alpha-mating factor and analog peptides. However, the folded conformation of alpha-mating factor is in equilibrium with predominantly unordered form, as found from the circular dichroism and NMR analyses. The N-H proton and C-alpha proton resonances of free alpha-mating factor as assigned in the present study allow the transferred nuclear Overhauser enhancement (NOE) analysis of the membrane-bound conformation that is more directly related with the activity.
mesh_terms: D000577:Amides / Q000302:isolation & purification; D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D000072235:Mating Factor; D010455:Peptides; D011487:Protein Conformation; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D000577:Amides; D010455:Peptides; D011522:Protons; D000072235:Mating Factor