NMR INVESTIGATION OF CYCLO(7,10)[C-7,X(9),C-10,NLE(12)] ANALOGS OF THE ALPHA-FACTOR FROM SACCHAROMYCES-CEREVISIAE

The cycle (7,10)[Cys(7),Cys(10),Nle(12)], cycle (7,10)[Cys(7),D-Ala(9),Cys(10),Nle(12)], and cyclo (7,10)[Cys(7),L-Ala(9),Cys(10),Nle(12)] analogues of the alpha-factor mating pheromone (WHWLQLKPGQPMY) of the yeast Saccharomyces cerevisiae were studied in DMSO/water (80 : 20) and aqueous solution by nmr spectroscopy. In addition, the cyclo (7,10)[Cys(7),D-Val(9),Cys(10),Nle 12] alpha-factor was examined in DMSO/water. Nuclear Overhauser effect (NOE) and NH d delta/dT data indicate that the cyclo (7,10)[CYS7,D-Val(9),Cys(10),Nle(12)] alpha-factor adopts a type II beta-turn in DMSO/water and that the cyclo (7,10)[Cys(7),D-Ala(9),Cys(10),Nle(12)] - and cyclo 7,10[Cys(7),L-Ala(9),Cys(10),Nle(12)] alpha-factor analogues adopt type II and type I/III beta-turns, respectively, in both DMSO/water and aqueous solutions. In aqueous solution, residues 8 and 9 of the cyclo (7,10)[Cys(7),Cys(10),Nle(12)] alpha-factor appear to adopt at least two distinct conformations, one of these being identified as a type I/III beta-turn. In contrast, the cyclo (7,10)[Cys(7),Cys(10),Nle(12)] alpha-factor appears to adopt predominately a type II beta-turn in DMSO/water. Quantitative NOE measurements of the cyclo (7,10)[Cys(7),Cys(10),Nle(12)] -, cyclo (7,10)[Cys(7),D-Val(9),Cys(10),Nle(12)]-, and cyclo (7,10)[Cys(7),L-ALa(9),Cys(10),Nle(12)] alpha-factors in DMSO/water were used to derive three-dimensional structures of the cyclo (7,10)[Cys(7),Pro(8),X(9),Cys(10)] portion of these analogues. (C) 1994 John Wiley & Sons, Inc.