Structure and Dynamics of Proteins from NMR Orientational Data

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9726341 Prestegard The overall objective of this work is to explore a potential new source of information on protein structure and dynamics in solution. The new information comes from residual dipolar couplings recently seen in NMR spectra of molecules with highly anisotropic magnetic susceptibilities when these molecules are placed in very high magnetic fields. The contributions are dependent on the orientation of the vector connecting the nuclei relative to the axes of a molecular susceptibility tensor. Measurement, thus, can provide structural information by constraining orientations of remote parts of large molecules in ways that are inaccessible using existing NOE based distance constraints. The couplings are also subject to the effects of motional averaging. This is particularly important because the range of motions contributing to the averaging process is much larger than those contributing to commonly measured NMR relaxation parameters. Experiments may, therefore, give insight into large amplitude, slower, motions that are among those most likely to contribute to protein function. Devising and testing methods for measurement and analysis of residual dipolar couplings is the primary object of this research. Two paramagnetic proteins, myoglobin and cytochrome b5, are chosen as targets for preliminary application. Both are well characterized structurally and should serve as suitable benchmarks for a new structural strategy. However, both have also been the subject of much debate as to motional contributions to function. Methods developed and applied to these proteins should contribute to resolution of this debate. ***