2ppf: Difference between revisions
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'''Reduced mutant D98N of AfNiR exposed to nitric oxide''' | '''Reduced mutant D98N of AfNiR exposed to nitric oxide''' | ||
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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] | 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: Alcaligenes faecalis]] | [[Category: Alcaligenes faecalis]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Murphy, M E.P.]] | [[Category: Murphy, M E.P.]] | ||
[[Category: Tocheva, E I.]] | [[Category: Tocheva, E I.]] | ||
[[Category: | [[Category: Bacteria]] | ||
[[Category: | [[Category: Copper]] | ||
[[Category: | [[Category: D98n]] | ||
[[Category: | [[Category: Denitrification]] | ||
[[Category: | [[Category: Nitric oxide]] | ||
[[Category: | [[Category: Nitrite reductase]] | ||
[[Category: | [[Category: Oxidoreductase]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 13:35:08 2008'' | |||
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Revision as of 13:35, 4 May 2008
Reduced mutant D98N of AfNiR exposed to nitric oxide
OverviewOverview
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.
About this StructureAbout this Structure
2PPF is a Single protein structure of sequence from Alcaligenes faecalis. Full crystallographic information is available from OCA.
ReferenceReference
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:17924665 Page seeded by OCA on Sun May 4 13:35:08 2008