5LQS: Structure Of Quinolinate Synthase Y21f Mutant In Complex With Substrate-derived Quinolinate

The enzyme NadA catalyzes the synthesis of quinolinic acid (QA), the precursor of the universal nicotinamide adenine dinucleotide (NAD) cofactor. Here, we report the crystal structures of complexes between the Thermotoga maritima (Tm) NadA K219R/Y107F variant and (i) the first intermediate (W) resulting from the condensation of dihydroxyacetone phosphate (DHAP) with iminoaspartate and (ii) the DHAP analogue and triose-phosphate isomerase inhibitor phosphoglycolohydroxamate (PGH). In addition, using the TmNadA K219R/Y21F variant, we have reacted substrates and obtained a crystalline complex between this protein and the QA product. We also show that citrate can bind to both TmNadA K219R and its Y21F variant. The W structure indicates that condensation causes dephosphorylation. We propose that catalysis by the K219R/Y107F variant is arrested at the W intermediate because the mutated protein is unable to catalyze its aldo-keto isomerization and/or cyclization that ultimately lead to QA formation. Intriguingly, PGH binds to NadA with its phosphate group at the site where the carboxylate groups of W also bind. Our results shed significant light on the mechanism of the reaction catalyzed by NadA.
PDB ID: 5LQSDownload
MMDB ID: 142703
PDB Deposition Date: 2016/8/17
Updated in MMDB: 2017/09
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 5LQS: monomeric; determined by author and by software (PISA)
Molecular Components in 5LQS
Label Count Molecule
Protein (1 molecule)
Quinolinate Synthase a(Gene symbol: TM1644)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB