Carboxyltransferase domain, subdomain A and B (IPR003778)

Short name: CT_A_B

Overlapping homologous superfamilies


Domain relationships



Urea carboxylase (UC) catalyses a two-step, ATP- and biotin-dependent carboxylation reaction of urea. It is composed of biotin carboxylase (BC), carboxyltransferase (CT), and biotin carboxyl carrier protein (BCCP) domains. The CT domain of UC consists of four subdomains, named A, B, C and D. This domain covers the A and B subdomains of the CT domain. This domain covers the whole length of KipA (kinase A) from Bacillus subtilis [PMID: 9334321]. It can also be found in S. cerevisiae urea amidolyase Dur1,2, which is a multifunctional biotin-dependent enzyme with domains for urea carboxylase and allophanate (urea carboxylate) hydrolase activity [PMID: 20884691].

KipA forms a complex with KipI, which is covered by the C and D subdomains of the CT. The KipI-KipA complex shares protein structure and sequence similarity with the CT domain of urea amidolyase from K. lactis, but residues that are important for CT catalysis are not conserved in KipA and KipI. Therefore, the KipA-KipI complex is unlikely to have CT activity [PMID: 22869039].

The CT domain is homologous to the Thermus thermophilus protein TTHA0988 (Q5SJM0). However, the subdomain order of TTHA0988 is different compared with that of CT, suggesting distinct fusion events in the evolution of these proteins [PMID: 22277658].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.