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PDBsum entry 1fs8
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Oxidoreductase
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PDB id
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1fs8
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Cytochrome c nitrite reductase from wolinella succinogenes. Structure at 1.6 a resolution, Inhibitor binding, And heme-Packing motifs.
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Authors
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O.Einsle,
P.Stach,
A.Messerschmidt,
J.Simon,
A.Kröger,
R.Huber,
P.M.Kroneck.
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Ref.
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J Biol Chem, 2000,
275,
39608-39616.
[DOI no: ]
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PubMed id
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Abstract
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Cytochrome c nitrite reductase catalyzes the 6-electron reduction of nitrite to
ammonia. This second part of the respiratory pathway of nitrate ammonification
is a key step in the biological nitrogen cycle. The x-ray structure of the
enzyme from the epsilon-proteobacterium Wolinella succinogenes has been solved
to a resolution of 1.6 A. It is a pentaheme c-type cytochrome whose heme groups
are packed in characteristic motifs that also occur in other multiheme
cytochromes. Structures of W. succinogenes nitrite reductase have been obtained
with water bound to the active site heme iron as well as complexes with two
inhibitors, sulfate and azide, whose binding modes and inhibitory functions
differ significantly. Cytochrome c nitrite reductase is part of a highly
optimized respiratory system found in a wide range of Gram-negative bacteria. It
reduces both anionic and neutral substrates at the distal side of a
lysine-coordinated high-spin heme group, which is accessible through two
different channels, allowing for a guided flow of reaction educt and product.
Based on sequence comparison and secondary structure prediction, we have
demonstrated that cytochrome c nitrite reductases constitute a protein family of
high structural similarity.
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Figure 1.
Fig. 1. Overall structure of nitrite reductase. A, front
view of the dimer of W. succinogenes cytochrome c nitrite
reductase. One monomer forms the asymmetric unit of the
crystals. Dimer formation is mediated by the central helical
segments. B, the arrangement of heme groups in the same
orientation as in A. In the left monomer, hemes are numbered
according to their attachment to the protein chain. In the right
monomer, distances are given between the iron atoms. Images were
produced with Molscript (32) and Raster3D (33).
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Figure 5.
Fig. 5. Heme-packing motifs. Superposition of the heme
groups of nitrite reductase (gray) and hydroxylamine
oxidoreductase (black) numbered according to their attachment to
the protein chain. With the exception of the active site heme (1
in NiR, 4 in hydroxylamine oxidoreductase), all heme groups form
di-heme elbow motifs ( circles), which are connected via a
parallel stacking arrangement similar to the one observed in
split-Soret cytochrome c (ovals). Images were produced using
Molscript (32).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2000,
275,
39608-39616)
copyright 2000.
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