Cloning, crystallization and preliminary characterization of a beta-carbonic anhydrase from Escherichia coli

Carbonic anhydrases are zinc metalloenzymes that fall into three distinct e volutionary and structural classes, alpha, beta and gamma. Although alpha-c lass enzymes, particularly mammalian carbonic anhydrase II, have been the s ubject of extensive structural studies, for the fi class, consisting of a w ide variety of prokaryotic and plant chloroplast carbonic anhydrases, the s tructural data is quite limited. A member of the beta class from E. coli (C ynT2) has been crystallized in native and selenomethionine-labelled forms a nd multiwavelength anomalous dispersion techniques have been applied in ord er to determine the positions of anomalous scatterers. The resulting phase information is sufficient to produce an interpretable electron-density map. A crystal structure for CynT2 would contribute significantly to the emergi ng structural knowledge of a biologically important class of enzymes that p erform critical functions in carbon fixation and prokaryotic metabolism.