4jre

Crystal structure of nitrate/nitrite exchanger NarK with nitrite bound

spinqualitylabelsall models 4jre, resolution 2.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4jre is a 6 chain structure with sequence from Escherichia coli K-12 and Mus musculus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.8Å Ligands: GYP, NO2 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function NARK_ECOLI Involved in excretion of nitrite produced by the dissimilatory reduction of nitrate. Publication Abstract from PubMed Mineral nitrogen in nature is often found in the form of nitrate (NO3(-)). Numerous microorganisms evolved to assimilate nitrate and use it as a major source of mineral nitrogen uptake. Nitrate, which is central in nitrogen metabolism, is first reduced to nitrite (NO2(-)) through a two-electron reduction reaction. The accumulation of cellular nitrite can be harmful because nitrite can be reduced to the cytotoxic nitric oxide. Instead, nitrite is rapidly removed from the cell by channels and transporters, or reduced to ammonium or dinitrogen through the action of assimilatory enzymes. Despite decades of effort no structure is currently available for any nitrate transport protein and the mechanism by which nitrate is transported remains largely unknown. Here we report the structure of a bacterial nitrate/nitrite transport protein, NarK, from Escherichia coli, with and without substrate. The structures reveal a positively charged substrate-translocation pathway lacking protonatable residues, suggesting that NarK functions as a nitrate/nitrite exchanger and that protons are unlikely to be co-transported. Conserved arginine residues comprise the substrate-binding pocket, which is formed by association of helices from the two halves of NarK. Key residues that are important for substrate recognition and transport are identified and related to extensive mutagenesis and functional studies. We propose that NarK exchanges nitrate for nitrite by a rocker switch mechanism facilitated by inter-domain hydrogen bond networks. Crystal structure of a nitrate/nitrite exchanger.,Zheng H, Wisedchaisri G, Gonen T Nature. 2013 May 30;497(7451):647-51. doi: 10.1038/nature12139. Epub 2013 May 12. PMID:23665960 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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