1as8: Difference between revisions

The structures of oxidized, reduced, nitrite-soaked oxidized and, nitrite-soaked reduced nitrite reductase from Alcaligenes faecalis have, been determined at 1.8-2.0 A resolution using data collected at -160, degrees C. The active site at cryogenic temperature, as at room, temperature, contains a tetrahedral type II copper site liganded by three, histidines and a water molecule. The solvent site is empty when crystals, are reduced with ascorbate. A fully occupied oxygen-coordinate nitrite, occupies the solvent site in crystals soaked in nitrite. Ascorbate-reduced, crystals soaked in a glycerol-methanol solution and nitrite at -40 degrees, C remain colorless at -160 degrees C but turn amber-brown when warmed, suggesting that NO is released. Nitrite is found at one-half occupancy., Five new solvent sites in the oxidized nitrite bound form exhibit defined, but different occupancies in the other three forms. These results support, a previously proposed mechanism by which nitrite is bound primarily by a, single oxygen atom that is protonable, and after reduction and cleavage of, that N-O bond, NO is released leaving the oxygen atom bound to the Cu site, as hydroxide or water.

1AS8 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Alcaligenes_faecalis Alcaligenes faecalis] with CU and NO2 as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Transferred_entry:_1.7.2.1 Transferred entry: 1.7.2.1], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.7.99.3 1.7.99.3] Structure known Active Sites: CU1, CU2, CU3, CU4, CU5 and CU6. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AS8 OCA].  

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