Crystal Structure of ChrR—A Quinone Reductase with the Capacity to Reduce Chromate

Subramaniam Eswaramoorthy (1) , Sébastien Poulain (2) , Rainer Hienerwadel (2, 3) , Nicolas Bremond (2, 4) , Matthew Sylvester (5) , Yian-Biao Zhang (1) , C. Berthomieu (6, 4) , Daniel van Der Lelie (7) , A. Matin (5)

1 BNL - Brookhaven National Laboratory [Upton, NY]
2 BVME - Biologie végétale et microbiologie environnementale - UMR7265
3 LGBP - Luminy Génétique et Biophysique des Plantes
4 IPM - Interactions Protéine Métal
5 Department of Microbiology and Immunology [Stanford]
6 BIAM - Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB)
7 NIH - National Institutes of Health [Bethesda]

The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as in chromate bioremediation. Its crystal structure, solved at 2.2 A ˚ resolution, shows that it belongs to the flavodoxin superfamily in which flavin mononucleotide (FMN) is firmly anchored to the protein. ChrR crystallized as a tetramer, and size exclusion chromatography showed that this is the oligomeric form that catalyzes chromate reduction. Within the tetramer, the dimers interact by a pair of two hydrogen bond networks, each involving Tyr128 and Glu146 of one dimer and Arg125 and Tyr85 of the other; the latter extends to one of the redox FMN cofactors. Changes in each of these amino acids enhanced chromate reductase activity of the enzyme, showing that this network is centrally involved in chromate reduction.

Keywords: Crystal structure; Quinones; Oxidation-reduction reactions; Bioremediation; Dimers (Chemical physics); Hydrogen bonding; Enzymes; Escherichia coli

Domains: Life Sciences [q-bio]

Subramaniam Eswaramoorthy, Sébastien Poulain, Rainer Hienerwadel, Nicolas Bremond, Matthew Sylvester, et al.. Crystal Structure of ChrR—A Quinone Reductase with the Capacity to Reduce Chromate. PLoS ONE, 2012, 7 (4), pp.e36017. ⟨10.1371/journal.pone.0036017⟩. ⟨cea-02019474⟩