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Structural views of quinone oxidoreductase from Mycobacterium tuberculosis reveal large conformational changes induced by the co‐factor
Author(s) -
Zheng Qianqian,
Song Yunlong,
Zhang Wei,
Shaw Neil,
Zhou Weihong,
Rao Zihe
Publication year - 2015
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13312
Subject(s) - oxidoreductase , chemistry , dimer , stereochemistry , quinone , conformational change , cofactor , substrate (aquarium) , enzyme , biochemistry , biology , ecology , organic chemistry
Energy generation, synthesis of biomass and detoxification of synthetic compounds are driven by electron transfer in all living organisms. Soluble quinone oxidoreductases ( QOR s) catalyze transfer of electrons from NADPH to substrates. The open reading frame Rv1454c of Mycobacterium tuberculosis ( Mtb ) encodes a NADPH ‐dependent QOR that is known to catalyze one‐electron reduction of quinones to produce semiquinones. Here, we report the crystal structures of the apo ‐enzyme of Mtb QOR and its binary complex with NADPH determined at 1.80 and 1.85 Å resolutions, respectively. The enzyme is bi‐modular. Domain I binds the substrate, while domain II folds into a typical Rossmann fold for tethering NADPH . Binding of NADPH induces conformational changes. Among the known structures of QOR s, Mtb QOR exhibits the largest conformational change. Movement of Phe41 to stack against Ala244 results in partial closure of the active site. Comparison of the structure with homologs suggests a conserved topology. However, differences are observed in the region around the site of hydride transfer, highlighting differences in substrate specificities amongst the homologs. Unliganded as well as NADPH ‐bound Mtb QOR crystallized as a dimer. Dimerization is mediated by homotypic intermolecular interactions involving main chain Cα as well as side‐chain atoms of residues. The results of analytical ultracentrifugation analysis revealed that Mtb QOR exists as a dimer in solution. Enzymatic assays indicate that Mtb QOR prefers 9,10‐phenanthrenequinone over 1,4‐benzoquinone as a substrate. The ability to reduce quinones probably assists Mtb in detoxification of a range of harmful chemicals encountered in the host during invasion. Database The coordinates and structure factors for apo‐ and NADPH ‐bound Mtb QOR have been deposited in the Protein Data Bank under accession codes 4RVS and 4RVU , respectively.