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N ‐methylleucine gramicidin‐S and (di‐ N ‐methylleucine) gramicidin‐S conformations with cis L ‐Orn‐ L ‐ N ‐MeLeu peptide bonds
Author(s) -
Patel Dinshaw J.,
Tonelli Alan E.
Publication year - 1976
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1976.360150815
Subject(s) - gramicidin s , gramicidin , chemistry , hydrogen bond , peptide , stereochemistry , peptide bond , crystallography , peptide conformation , molecule , organic chemistry , biochemistry , membrane
Conformations containing all trans peptide bonds have previously been proposed for N ‐methylleucine gramicidin‐S and (di‐ N ‐methylleucine) gramicidin‐S based on an evaluation of proton nuclear magnetic resonance parameters in a series of solvents. These gramicidin‐S derivatives exhibit full biological activity despite the fact that the proposed solution conformations differ in backbone topology and relative orientation of the Phe and Orn side chains compared to gramicidin‐S. The present authors discuss conformations for N ‐methylleucine gramicidin‐S and (di‐ N ‐methylleucine) gramicidin‐S which incorporate cis peptide bonds at L ‐Orn‐ L ‐ N ‐MeLeu, where the gramicidin‐S backbone is essentially retained, and the relative orientation of the Pro, Orn, Val, and Phe side chains correspond to those observed for gramicidin‐S. A novel hydrogen‐bond arrangement involving one carbonyl group interacting with two peptide protons (1 ←4 and 1 ←5 types) is proposed to stabilize the backbone conformation in the gramicidin‐S derivatives. A recent report on the cyclic heptapeptide antibiotic, Ilamycin B 1 , shows the presence of cis peptide bonds at N‐CH 3 amino acids, as well as the novel hydrogen‐bond arrangement presented above.