Determination of membrane peptide orientation by 1H-detected 2H NMR spectroscopy

We demonstrate the application of the proton inverse detected deuteron (PRIDE) NMR technique to the measurement of the orientation of membrane-bound peptides with enhanced sensitivity. Gramicidin D, a transmembrane peptide, and ovispirin, a surface-bound peptide, were used as model systems. The peptides were H-2-labeled by H-1/H-2 exchange and oriented uniaxially on glass plates. The directly detected H-2 spectra of both peptides showed only a strong D2O signal and no large quadrupolar splittings. In contrast, the PRIDE spectrum of gramicidin exhibited quadrupolar splittings as large as 281 kHz, consistent with its transmembrane orientation. Moreover, the large D2O signal in the directly detected H-2 spectra was cleanly suppressed in the PRIDE spectrum. For ovispirin, the H-1 indirectly detected H-2 spectrum revealed a 104 kHz splitting and a zero-frequency peak. The former reflects the in-plane orientation of most of the helix axis, while the latter results from residues with a magic-angle orientation of the N-D bonds. These are consistent with previous N-15 NMR results on ovispirin. The combination of PRIDE and exchange labeling provides an economical and sensitive method of studying membrane peptide orientations in lipid bilayers without the influence of D2O and with the ability to detect N-D bonds at the magic angle from the bilayer normal. (C) 2002 Elsevier Science (USA).