Taxonomic distribution of proteins containing CPSase_L_D3 domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing CPSase_L_D3 domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

The structure of carbamoyl phosphate synthetase determined to 2.1 Aresolution.

Thoden JB, Raushel FM, Benning MM, Rayment I, Holden HM
Acta Crystallogr D Biol Crystallogr. 1999; 55: 8-24

Carbamoyl phosphate synthetase catalyzes the formation of carbamoylphosphate from one molecule of bicarbonate, two molecules of Mg2+ATP andone molecule of glutamine or ammonia depending upon the particular form ofthe enzyme under investigation. As isolated from Escherichia coli, theenzyme is an alpha,beta-heterodimer consisting of a small subunit thathydrolyzes glutamine and a large subunit that catalyzes the two requiredphosphorylation events. Here the three-dimensional structure of carbamoylphosphate synthetase from E. coli refined to 2.1 A resolution with an Rfactor of 17.9% is described. The small subunit is distinctly bilobal witha catalytic triad (Cys269, His353 and Glu355) situated between the twostructural domains. As observed in those enzymes belonging to thealpha/beta-hydrolase family, the active-site nucleophile, Cys269, isperched at the top of a tight turn. The large subunit consists of fourstructural units: the carboxyphosphate synthetic component, theoligomerization domain, the carbamoyl phosphate synthetic component andthe allosteric domain. Both the carboxyphosphate and carbamoyl phosphatesynthetic components bind Mn2+ADP. In the carboxyphosphate syntheticcomponent, the two observed Mn2+ ions are both octahedrally coordinated byoxygen-containing ligands and are bridged by the carboxylate side chain ofGlu299. Glu215 plays a key allosteric role by coordinating to thephysiologically important potassium ion and hydrogen bonding to the ribosehydroxyl groups of ADP. In the carbamoyl phosphate synthetic component,the single observed Mn2+ ion is also octahedrally coordinated byoxygen-containing ligands and Glu761 plays a similar role to that ofGlu215. The carboxyphosphate and carbamoyl phosphate synthetic components,while topologically equivalent, are structurally different, as would beexpected in light of their separate biochemical functions.