Temperature-dependent protein backbone dynamics from auto- and cross-correlated NMR relaxation rates

Abstract

The temperature dependence of nuclear magnetic resonance relaxation rates was investigated for the backbone of tSN/~3C labeled human ubiquitin in the temperature range of 20-50 ~ The ~SN autorelaxation rates give evidente that the potential energy functions for ~SN-HN bonds ate not quadratic, in agreement with results for other proteins. Cross-correlation rates arising from correlated fluctuations of two ~SN-HN dipole~iipole interactions involving successive residues were obtained by the method of Petupessy et al. (E Pelupessy, S. Ravindranathan, G. Bodenhausen: J. Biomol. NMR 25, 265-280, 2003). The results suggest the presente of slow internal motions at 50 ~