Steve Ealick's Research Group

Thermotoga maritima PurL

PDB files:

2HRU: TmPurL complexed with ADP

2HRY: TmPurL complexed with AMP-PCP

2HS0: TmPurL complexed with ATP

2HS3: TmPurL complexed with FGAR

2HS4: TmPurL complexed with FGAR and AMP-PCP


Formylglycinamide ribonucleotide amidotransferase (FGAR-AT; encoded by the purL gene) catalyzes the ATP-dependent synthesis of formylglycinamidine ribonucleotide (FGAM) from formylglycinamide ribonucleotide (FGAR) and glutamine in the fourth step of the purine biosynthetic pathway. Two types of PurL have been detected. Large PurL (lgPurL) is found in eukaryotes and Gram-negative bacteria, and consists of a single 140 kDa polypeptide chain. Small PurL (smPurL), is found in archaea and Gram-positive bacteria and consists of an approximately 80 kDa polypeptide chain. Small PurL requires two additional gene products, PurQ and PurS, for activity.

Themotoga maritima PurL (TmPurL) is a smPurL (63 kDa) with a fold that is very similar to that of the FGAM synthetase domain of the large Salmonella typhimurium PurL (StPurL). As in the FGAM synthetase domain of StPurL, TmPurL can be divided into four subdomains.


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TmPurL is a member of the PurM superfamily of ATP-utilizing enzymes that contain the DX4GAXP motif identified through BLAST searches and multiple sequence alignments. The family that contains a novel ATP-binding domain. The ChemDraw representation of the active site shows residues labeled in red that are highly conserved among small and large PurLs. D94 is the aspartate of the signature binding motif, DX4GAXP, is boxed in light pink.

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Morar M, Anand R, Hoskins AA, Stubbe J and Ealick SE. Complexed Structures of Formylglycinamide Ribonucleotide Amidotransferase from Thermotoga maritima Describe a Novel ATP-binding Protein Superfamily. Biochemistry 45:14880-14895 (2006).


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