Alteration of the quaternary structure of glutamate dehydrogenase from Clostridium symbiosum by a single mutation distant from the subunit interfaces

Abstract

X-ray crystallographic studies have previously shown that glutamate dehydrogenase from Clostridium symbiosum is a homohexamer. Mutation of the active-site aspartate-165 to histidine causes an alteration in the structural properties of the enzyme. The mutant enzyme, D165H exists predominantly as a single species of lower molecular mass than the wild-type enzyme as indicated by gel filtration and sedimentation velocity analysis. The latter technique gives an s20,w value for D165H of (6.07 ± 0.01)S which compares with (11.08 ± 0.01)S for the wild-type, indicative of alteration of the homohexameric quaternary structure of the native enzyme to a dimeric form, a result confirmed by sedimentation equilibrium experiments. Further support for this is provided by chemical modification by Ellman's reagent of cysteine-144 in the mutant, a residue which is buried at the dimer-dimer interface in the wild-type enzyme and is normally inaccessible to modification. The results suggest a possible structural route for communication between the active sites and subunit interfaces which may be important for relaying signals between subunits in allosteric regulation of the enzyme.

DOI: 10.1007/s002490050055

Cite this paper

@article{Dean1997AlterationOT, title={Alteration of the quaternary structure of glutamate dehydrogenase from Clostridium symbiosum by a single mutation distant from the subunit interfaces}, author={Jonathan L. E. Dean and Helmut C{\"{o}lfen and Stephen Harding and David W. Rice and P. C. Engel}, journal={European Biophysics Journal}, year={1997}, volume={25}, pages={417-422} }