Predicting NMR relaxation rates in anisotropically tumbling proteins through networks of coupled rotators.

We show that the prediction of (15)N relaxation rates in proteins can be extended to systems with anisotropic global rotational diffusion by using a network of coupled rotators (NCR), starting from a three-dimensional structure. The relaxation rates predicted by this method are confronted in several examples with experiments performed by other groups. The NCR spectral density functions are compared with the results obtained from reduced spectral density mapping. The consequence of the timescales of internal motions on the predicted relaxation rates and the effects of the predicted local anisotropy-present only in the case of anisotropic overall tumbling-on dynamic parameters, are discussed.