PICOSECOND DYNAMICAL CHANGES ON DENATURATION OF YEAST PHOSPHOGLYCERATE KINASE REVEALED BY QUASI-ELASTIC NEUTRON-SCATTERING

Quasielastic neutron scattering experiments performed on yeast phospho glycerate kinase in the native form and denatured in 1.5 M guanidinium chloride reveal a change in the fast (picosecond time scale) diffusiv e internal dynamics of the protein, The momentum and energy transfer d ependences of the scattering for both states are fitted by an analytic al model in which, on the experimentally accessible picosecond time sc ale and angstrom length scale, the dynamics of a fraction of the nonex changeable hydrogens in the protein is described as a superposition of vibrations with uniform diffusion in a sphere, the rest of the hydrog ens undergoing only vibrational motion. The fraction diffusing changes , from similar to 60% in the native protein to similar to 82% in the d enatured protein, The radius of the sphere also changes slightly from similar to 1.8 Angstrom in the native protein to similar to 2.2 Angstr om in the denatured protein. Possible implications of these results fo r the general protein folding problem are discussed. (C) 1997 Wiley-Li ss, Inc.