1r27: Difference between revisions

[[Image:1r27.gif|left|200px]]<br /><applet load="1r27" size="350" color="white" frame="true" align="right" spinBox="true"  

The structure of the catalytic and electron-transfer subunits (NarGH) of the integral membrane protein, respiratory nitrate reductase (Nar) has been determined to 2.0 A resolution revealing the molecular architecture of this Mo-bisMGD (molybdopterin-guanine-dinucleotide) containing enzyme which includes a previously undetected FeS cluster. Nar, together with the related enzyme formate dehydrogenase (Fdh-N), is a key enzyme in the generation of proton motive force across the membrane in Escherichia coli nitrate respiration. A comparative study revealed that Nar and Fdh-N employ different approaches for acquiring substrate, reflecting different catalytic mechanisms. Nar uses a very narrow and nonpolar substrate-conducting cavity with a nonspecific substrate binding site, whereas Fdh-N accommodates a wider, positively charged substrate-conducting cavity with a more specific substrate binding site. The Nar structure also demonstrates the first example of an Asp side chain acting as a Mo ligand providing a structural basis for the classification of Mo-bisMGD enzymes.

1R27 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MO:'>MO</scene>, <scene name='pdbligand=F3S:'>F3S</scene>, <scene name='pdbligand=SF4:'>SF4</scene> and <scene name='pdbligand=MGD:'>MGD</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Nitrate_reductase Nitrate reductase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.7.99.4 1.7.99.4] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1R27 OCA].  

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