Crystal structure of Nitrate Reductase A, NarGHI, from Escherichia coli
[NARG_ECOLI] The nitrate reductase enzyme complex allows E.coli to use nitrate as an electron acceptor during anaerobic growth. The alpha chain is the actual site of nitrate reduction. [NARI_ECOLI] The nitrate reductase enzyme complex allows E.coli to use nitrate as an electron acceptor during anaerobic growth. The gamma chain is a membrane-embedded heme-iron unit resembling cytochrome b, which transfers electrons from quinones to the beta subunit. [NARH_ECOLI] The nitrate reductase enzyme complex allows E.coli to use nitrate as an electron acceptor during anaerobic growth. The beta chain is an electron transfer unit containing four cysteine clusters involved in the formation of iron-sulfur centers. Electrons are transferred from the gamma chain to the molybdenum cofactor of the alpha subunit.
Publication Abstract from PubMed
The facultative anaerobe Escherichia coli is able to assemble specific respiratory chains by synthesis of appropriate dehydrogenases and reductases in response to the availability of specific substrates. Under anaerobic conditions in the presence of nitrate, E. coli synthesizes the cytoplasmic membrane-bound quinol-nitrate oxidoreductase (nitrate reductase A; NarGHI), which reduces nitrate to nitrite and forms part of a redox loop generating a proton-motive force. We present here the crystal structure of NarGHI at a resolution of 1.9 A. The NarGHI structure identifies the number, coordination scheme and environment of the redox-active prosthetic groups, a unique coordination of the molybdenum atom, the first structural evidence for the role of an open bicyclic form of the molybdo-bis(molybdopterin guanine dinucleotide) (Mo-bisMGD) cofactor in the catalytic mechanism and a novel fold of the membrane anchor subunit. Our findings provide fundamental molecular details for understanding the mechanism of proton-motive force generation by a redox loop.
Insights into the respiratory electron transfer pathway from the structure of nitrate reductase A.,Bertero MG, Rothery RA, Palak M, Hou C, Lim D, Blasco F, Weiner JH, Strynadka NC Nat Struct Biol. 2003 Sep;10(9):681-7. Epub 2003 Aug 10. PMID:12910261
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.