Crystallization of the NADP+-dependent glutamate dehydrogenase from Escherichia coli

Abstract The NADP + -dependent hexameric glutamate dehydrogenase from Escherichia coli has been crystallized as the apo-enzyme and also in the presence of its substrates 2-oxoglutarate, glutamate or NADP + , using either pulsed equilibrium microdialysis, or the hanging drop method of vapour diffusion. Three non-isomorphous, but related, crystal forms have been obtained, all of which belong to the orthorhombic system and are most likely to be in space group P 2 1 2 1 2 1 . One crystal form is grown from ammonium sulphate, includes the apo-enzyme and the binary complexes with 2-oxoglutarate or NADP + , and has cell dimensions a = 157·5 A, b = 212·5 A, c = 101·0 A with a hexamer in the asymmetric unit. Crystallizations using glutamate as the precipitant produced two further crystal forms, which show significant changes in the b and c cell dimensions with respect to the apo-enzyme crystals, with parameters a = 160·0 A, b =217·5 A c = 92·4 A and a = 160·0 A, b = 223·0 A c = 92·4 A, respectively. X-ray diffraction photographs taken with synchrotron radiation show measurable reflections to beyond 3·0 A resolution.