Open AccessActive‐site models for complexes of quinolinate synthase with substrates and intermediates
Author(s) -
Soriano Erika V.,
Zhang Yang,
Colabroy Keri L.,
Sanders Jennie M.,
Settembre Ethan C.,
Dorrestein Pieter C.,
Begley Tadhg P.,
Ealick Steven E.
Publication year - 2013
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s090744491301247x
Subject(s) - pyrococcus furiosus , pyrococcus horikoshii , quinolinate , chemistry , stereochemistry , dna ligase , active site , atp synthase , biochemistry , biosynthesis , enzyme , gene , amino acid , archaea , tryptophan , quinolinic acid
Quinolinate synthase (QS) catalyzes the condensation of iminoaspartate and dihydroxyacetone phosphate to form quinolinate, the universal precursor for the de novo biosynthesis of nicotinamide adenine dinucleotide. QS has been difficult to characterize owing either to instability or lack of activity when it is overexpressed and purified. Here, the structure of QS from Pyrococcus furiosus has been determined at 2.8 Å resolution. The structure is a homodimer consisting of three domains per protomer. Each domain shows the same topology with a four‐stranded parallel β‐sheet flanked by four α‐helices, suggesting that the domains are the result of gene triplication. Biochemical studies of QS indicate that the enzyme requires a [4Fe–4S] cluster, which is lacking in this crystal structure, for full activity. The organization of domains in the protomer is distinctly different from that of a monomeric structure of QS from P. horikoshii [Sakuraba et al. (2005), J. Biol. Chem. 280 , 26645–26648]. The domain arrangement in P. furiosus QS may be related to protection of cysteine side chains, which are required to chelate the [4Fe–4S] cluster, prior to cluster assembly.