The effect of selective deuteration on magnetization transfer in larger proteins.

The effects of selective deuteration on calculated NOESY intensities have been analyzed for the structure of the E. coli trp aporepressor, a 25 kDa protein. It is shown that selectively deuterated trp aporepressor proteins display larger calculated NOESY intensities than those for the same interproton distances in the natural abundance protein. The relatively larger magnetization transfer is demonstrated by a comparison of the NOE build-up curves for specific proton pairs, and for the calculated NOE intensities of short-range NOEs to backbone amide protons. This increase in intensity is especially pronounced for the NHi-NHi+1 cross peaks in the alpha-helical regions, and particularly for amide protons of two sequential deuterated residues. The effect is shown to be further intensified for longer mixing times. It is also shown that in all cases, each amide proton exhibits stronger NOEs to its own side chain, with an enhanced effect for deuterated derivatives. This theoretical analysis demonstrates that an evaluation of the relative NOE intensities for different selectively deuterated analogs may be an important tool in assigning NMR spectra of large proteins. These results also serve as a guide for the interpretation of NOEs in terms of distances for structure calculations based on data using selectively deuterated proteins.