InterPro domain: IPR033828

This entry represents the type 1 glutamine amidotransferase (GATase1) domain found in Cytidine Triphosphate Synthetase (CTP). CTP is involved in pyrimidine ribonucleotide/ribonucleoside metabolism. CTPs produce CTP from UTP and glutamine and regulate intracellular CTP levels through interactions with four ribonucleotide triphosphates. The enzyme exists as a dimer of identical chains that aggregates as a tetramer [ 1 ].

CTP is derived form UTP in three separate steps involving two active sites. In one active site, the UTP O4 oxygen is activated by Mg-ATP-dependent phosphorylation, followed by displacement of the resulting 4-phosphate moiety by ammonia. At a separate site, ammonia is generated via rate limiting glutamine hydrolysis (glutaminase) activity [ 2 ]. A gated channel that spans between the glutamine hydrolysis and amidoligase active sites provides a path for ammonia diffusion. CTPs belong to the triad family of amidotransferases having a conserved Cys-His-Glu catalytic triad in the glutaminase active site [ 3 ].

1. Crystal structure of Escherichia coli cytidine triphosphate synthetase, a nucleotide-regulated glutamine amidotransferase/ATP-dependent amidoligase fusion protein and homologue of anticancer and antiparasitic drug targets. Biochemistry 43, 6447-63
2. Structural role for a conserved region in the CTP synthetase glutamine amide transfer domain. J. Bacteriol. 169, 3023-8
3. The amidotransferase family of enzymes: molecular machines for the production and delivery of ammonia. Biochemistry 38, 7891-9