Phosphoribosylformylglycinamidine synthase subunit PurS (IPR003850)

Short name: PurS

Overlapping homologous superfamilies

Family relationships



Phosphoribosylformylglycinamidine(FGAM) synthetase, EC:, catalyses the fourth step in the de novo purine biosynthetic pathway [PMID: 15301532].

5-phosphoribosylformylglycinamide (FGAR) + glutamine + ATP = FGAM + glutamate + ADP + Pi

In eukaryotes and many bacterial systems (including Escherichia coli and Salmonella typhimurium), the FGAM synthetase is encoded by the large form of PurL (lgPurL), which contains an N-terminal ATPase domain and a C-terminal glutamine-binding domain. In archaeal and other bacterial systems, however, FGAM synthetase is encoded by separate genes, making it a multisubunit (rather than multidomain) enzyme. The protein is composed of the small form of PurL (smPurL), which is homologus to the ATPase domain of lgPurL, PurQ which is homologous to the glutamine-binding domain of of lgPurL, and PurS, whose function is not known.

This entry represents the PurS subunit (also known as YexA) of the multisubunit FGAM synthetase. Recent studies showed that disruption of the purS gene in Bacillus subtilis resulted in a purine auxotrophic phenotype, due to defective FGAM synthetase activity [PMID: 10784038]. Therefore, the PurS protein appears to be required for the function of the PurL and PurQ subunits of the FGAM synthetase, but the molecular mechanism for the functional role of PurS is currently not known.

Contributing signatures

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