Orotate phosphoribosyltransferase (OPRTase) is involved in the de novo biosynthesis of pyrimidine nucleotides by catalyzing the Mg2+ dependent formation of orotidine 5‘-monophosphate (OMP), from which uridine 5‘-monophosphate is synthesized. Crystal structure of OPRTase from Vibrio cholerae O1 biovar eltor str. N16961 has been solved and refined to 2.1 Å resolution. The asymmetric unit contains eight molecules, which pack in two tetramers (ABCD and EFGH). Total buried surface area of both oligomers is about 9500 squared Angstroms. In each tetramer two types of dimers are observed. For example, in ABCD tetramer there are AB (2670 sq. A), AC
IDP90785 shares about 20 % sequence homology with IDP04423, an OPRTase from Bacillus anthracis. Pairwise structure alignment of two IDPs reveals the lowest rmsd of 2.5 Angstrom.