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Crystal Structures of Quinolinate Synthase in Complex with a Substrate Analogue, the Condensation Intermediate, and Substrate-Derived Product
journal contribution
posted on 2016-08-22, 00:00 authored by Anne Volbeda, Claudine Darnault, Oriane Renoux, Debora Reichmann, Patricia Amara, Sandrine Ollagnier
de Choudens, Juan C. Fontecilla-CampsThe 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.
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NADSubstrate AnalogueSubstrate-Derived ProductK 219R variantcarboxylate groupsTm NadA K 219R variantnicotinamide adenine dinucleotideQA formationThermotoga maritimaQuinolinate Synthasetriose-phosphate isomerase inhibitor phosphoglycolohydroxamateQA productCondensation IntermediateNadA K 219R variantquinolinic acidenzyme NadA catalyzesY 21F variantTm NadA K 219Rcrystal structuresphosphate groupPGHdihydroxyacetone phosphatecondensation causes dephosphorylationW structureDHAP analoguecrystal Structures
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