Diversity of the gramicidin a spatial structure: two-dimensional 1H nmr study in solution

Abstract

Theoretical consideration reveals a unique relationship between NMR spectral parameters and possible types of the gramididin A spatial structure. By means of two dimensional NMR spectroscopy four distinct species were detected simultaneously in ethanol solution. Comparison of experimental data and theoretical conclusions demonstrates that species 1 and 2 are left-handed parallel double helices ▪ differing in relative arrangement of the two polypeptide chains within the dimers, species 3 is left-handed antiparallel double helix ▪, and species 4 is a mirror image of species 1, i.e. right-handed parallel double helix ▪. The results are compared with those on spatial structures of the peptide in complex with cesium (right-handed antiparallel double helix ▪) and of the gramicidin A transmembrane ionchannel (N-terminal to N-terminal single-stranded dimer ▪).