Crystallization of the catalytic subunit of Saccharomyces cerevisiae acetohydroxyacid synthase

Acetohydroxyacid synthase (AHAS; E.C. 4.1.3.18) is the first enzyme in the biosynthetic pathway of the branched-chain amino acids isoleucine, leucine and valine. It is a thiamin diphosphate-dependent enzyme which catalyses the decarboxylation of pyruvate and its condensation with either 2-ketobutyrate or a second molecule of pyruvate to give 2-aceto-2-hydroxybutyrate or 2-acetolactate, respectively. The enzyme is the target of sulfonylurea and imidazolinone herbicides, which act as potent and specific inhibitors. Here, the crystallization and preliminary X-ray diffraction analysis of the catalytic subunit of Saccharomyces cerevisiae AHAS is reported. Data to 2.7 Angstrom resolution have been collected using synchrotron radiation (Advanced Photon Source, Chicago). Crystals have unit-cell parameters a = 95.8, b = 110.0, c = 178.9 Angstrom and belong to the space group P2(1)2(1)2(1). Preliminary analysis indicates there is one dimer located in each asymmetric unit.