CRYSTALLIZATION OF ACETATE KINASE FROM METHANOSARCINA-THERMOPHILA ANDPREDICTION OF ITS FOLD

The unique biochemical properties of acetate kinase present a classic conundrum in the study of the mechanism of enzyme-catalyzed phosphoryl transfer. Large, single crystals of acetate kinase from Methanosarcin a thermophila were grown from a solution of ammonium sulfate in the pr esence of ATF. The crystals diffract to beyond 1.7 Angstrom resolution . Analysis of X-ray data from the crystals is consistent with a space group of C2 and unit cell dimensions a = 181 Angstrom, b = 67 Angstrom , c = 83 Angstrom, beta = 103 degrees. Diffraction data have been coll ected from the crystals at 110 and 277 K. Data collected at 277 K exte nd to lower resolution, but are more reproducible. The orientation of a noncrystallographic twofold axis of symmetry has been determined. Ba sed on an analysis of the predicted amino acid sequences of acetate ki nase from several organisms, we hypothesize that acetate kinase is a m ember of the sugar kinase/actin/hsp70 structural family.