2ppf: Difference between revisions

|PDB= 2ppf |SIZE=350|CAPTION= <scene name='initialview01'>2ppf</scene>, resolution 1.65&Aring;

|SITE=  

|LIGAND= <scene name='pdbligand=CU1:COPPER+(I)+ION'>CU1</scene>, <scene name='pdbligand=CU:COPPER+(II)+ION'>CU</scene>, <scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=NO:NITROGEN+OXIDE'>NO</scene> and <scene name='pdbligand=TRS:2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL'>TRS</scene>

|ACTIVITY= [http://en.wikipedia.org/wiki/Nitrite_reductase_(NO-forming) Nitrite reductase (NO-forming)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.7.2.1 1.7.2.1]  

|GENE= nirK, nir ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=511 Alcaligenes faecalis])

 

 

==Overview==

Nitrite reductase (NiR) is an enzyme that uses type 1 and type 2 copper sites to reduce nitrite to nitric oxide during bacterial denitrification. A copper-nitrosyl intermediate is a proposed, yet poorly characterized feature of the NiR catalytic cycle. This intermediate is formally described as Cu(I)-NO+ and is proposed to be formed at the type 2 copper site after nitrite binding and electron transfer from the type 1 copper site. In this study, copper-nitrosyl complexes were formed by prolonged exposure of exogenous NO to crystals of wild-type and two variant forms of NiR from Alcaligenes faecalis (AfNiR), and the structures were determined to 1.8 A or better resolution. Exposing oxidized wild-type crystals to NO results in the reverse reaction and formation of nitrite that remains bound at the active site. In a type 1 copper site mutant (H145A) that is incapable of electron transfer to the type 2 site, the reverse reaction is not observed. Instead, in both oxidized and reduced H145A crystals, NO is observed bound in a side-on manner to the type 2 copper. In AfNiR, Asp98 forms hydrogen bonds to both substrate and product bound to the type 2 Cu. In the D98N variant, NO is bound side-on but is more disordered when observed for the wild-type enzyme. The solution EPR spectra of the crystallographically characterized NiR-NO complexes indicate the presence of an oxidized type 2 copper site and thus are interpreted as resulting from stable copper-nitrosyls and formally assigned as Cu(II)-NO-. A reaction scheme in which a second NO molecule is oxidized to nitrite can account for the formation of a Cu(II)-NO- species after exposure of the oxidized H145A variant to NO gas.

 

2PPF is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Alcaligenes_faecalis Alcaligenes faecalis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2PPF OCA].

 

Stable copper-nitrosyl formation by nitrite reductase in either oxidation state., Tocheva EI, Rosell FI, Mauk AG, Murphy ME, Biochemistry. 2007 Oct 30;46(43):12366-74. Epub 2007 Oct 9. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/17924665 17924665]

[[Category: Nitrite reductase (NO-forming)]]

[[Category: Single protein]]

[[Category: Murphy, M E.P.]]

[[Category: Tocheva, E I.]]

[[Category: bacteria]]