A study of protein side-chain dynamics from new 2H auto-correlation and 13C cross-correlation NMR experiments:: Application to the N-terminal SH3 domain from drk

Two new NMR experiments are presented for measuring side-chain dynamics in proteins. The first method, requiring N-15, C-13, similar to 50% H-2-labeled protein, measures H-2 T-1 and T-1 rho spin relaxation times at side-chain positions. A second experiment permits the straightforward measurement of C-13-H-1 dipole-dipole cross-correlation relaxation rates at C-13(beta) positions in N-15, C-13-labeled molecules. An excellent correlation is observed between order parameters, describing the amplitude of motion at these sites, obtained on the basis of 2H relaxation and dipole-dipole cross-correlation relaxation rates. Together these experiments provide a powerful approach for selecting appropriate motional models. The methods are applied to study the side-chain motional properties of the N-terminal SH3 domain from the signaling protein drk. (C) 1998 Academic Press Limited.