Crystallization and preliminary X-ray diffraction analysis of the hyperthermostable NAD-dependent glutamate dehydrogenase from Pyrobaculum islandicum.

ABSTRACT

NAD-dependent glutamate dehydrogenase from the hyperthermophilic archaeon Pyrobaculum islandicum was crystallized in the apo- and holoenzyme forms. Crystals were obtained using 2-propanol and polyethylene glycol MME 550 as precipitants for the apoenzyme and holoenzyme, respectively. The apoenzyme crystals belong to the trigonal space group P3(1)21 or its enantiomorph P3(2)21. The asymmetric unit contains three subunits; the values of the Matthews coefficient (VM) and the solvent content are 2.9 A3 Da-1 and 57%, respectively. A native data set was collected to a highest resolution limit of 4.0 A on an in-house X-ray source using a rotating-anode generator (overall Rsym of 12.3% and completeness of 97%). The holoenzyme crystals belong to the orthorhombic space group P2(1)2(1)2(1); the asymmetric unit contains one hexamer, giving a VM of 2.79 A3 Da-1 and a solvent content of 55%. Native and derivative data sets were collected. The crystals diffract to a maximum resolution of 2.8 A on the KEK-NW12 beamline at the Photon Factory and gave a data set with an overall Rsym of 7.9% and a completeness of 91%. Attempts are being made to solve the structure by the SIRAS method.