15N,(1)H Heteronuclear correlation NMR of gramicidin A in DMPC-d(67).
We have studied gramicidin A, an environmentally sensitive polymorphic pentadecapeptide, fully 15N-labelled and dispersed in a highly deuterated phospholipid bilayer system. By submitting the sample to fast magic angle spinning, we were able to reduce the polypeptide amide hydrogen linewidths to 160 Hz, and hence to partially resolve them. By correlating these resonances with the 40 Hz wide dipolar coupled 15N in a 2D-CROPSY (cross-polarization spectroscopy) experiment, it was possible to observe the 20 partially overlapping 1H-15N signal pairs from the polypeptide backbone and sidechains. Both chemical shift distributions closely match those of the same peptide in SDS micelles, but only poorly match those of conformationally different gramicidin A in trifluoroethanol, dimethylsulfoxide, or methanol/chloroform mixture. Our results are indicative of the N-to-N right-handed beta6.3-helix conformation of gramicidin A and offer sufficient resolution to encourage development of experiments to measure orientational or distance restraints using through-space dipolar couplings.
Farès
Christophe
C
Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Sharom
Frances J
FJ
Davis
James H
JH
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D006096:Gramicidin / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008823:Micelles; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011522:Protons
D000900:Anti-Bacterial Agents; D008051:Lipid Bilayers; D008565:Membrane Proteins; D008823:Micelles; D009587:Nitrogen Isotopes; D011522:Protons; D006096:Gramicidin; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine