3svl
From Proteopedia
Structural basis of the improvement of ChrR - a multi-purpose enzyme
Structural highlights
Function[CHRR_ECOLI] Involved in the protection against chromate toxicity. Catalyzes the transfer of three electrons to Cr(6+) producing Cr(3+) and one electron to molecular oxygen without producing the toxic Cr(5+) species and only producing a minimal amount of reactive oxygen species (ROS). It can also reduce quinones, potassium ferricyanide, 2,6-dichloroindophenol, V(5+), Mo(6+), methylene blue and cytochrome c. The quinone reductase activity may protect against oxidative stress by preventing redox cycling of quinones which would otherwise generate ROS and by maintaining a pool of reduced quinone in the cell that is able to quench ROS directly. It is able to use both NAD or NADP equally well.[1] [2] [3] [4] Publication Abstract from PubMedThe 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. Crystal Structure of ChrR-A Quinone Reductase with the Capacity to Reduce Chromate.,Eswaramoorthy S, Poulain S, Hienerwadel R, Bremond N, Sylvester MD, Zhang YB, Berthomieu C, Van Der Lelie D, Matin A PLoS One. 2012;7(4):e36017. Epub 2012 Apr 27. PMID:22558308[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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