2.7.2.8 of the recombinant wild type protein, the selenomethionine substituted enzyme, the mutants and the methylated enzyme, cocrystallization with ATP, ADP, acetyl-CoA, CoA, N-acetyl-L-glutamate, adenylylimidodiphosphate, arginine 671144 2.7.2.8 purified enzyme in complex with L-arginine, sitting drop vapor diffusion method, mixing of 10 mg/ml protein in 50 mM Tris-HCl, pH 8.0, 50 mM NaCl, 10% glycerol, 5 mM 2-mercaptoethanol, and 1 mM EDTA with 1 mM L-arginine, and 10 mM N-acetyl-L-glutamate for 30 min, 0.002 ml of this protein solution is mixed with 0.002 ml of reservoir solution containing 100 mM sodium cacodylate trihydrate, pH 6.2, 25% PEG P400 and 200 mM magnesium chloride, X-ray diffraction structure determination and analysis at 2.8 A resolution. In contrast to the structure of mmNAGS/K in the absence of L-arginine where there are conformational differences between the four subunits in the asymmetric unit, all four subunits in the L-arginine liganded structure have very similar conformations 735596 2.7.2.8 without arginine 675366