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PDBsum entry 1qla
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Oxidoreductase
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PDB id
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1qla
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Contents |
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655 a.a.
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239 a.a.
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254 a.a.
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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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Structure of fumarate reductase from wolinella succinogenes at 2.2 a resolution.
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Authors
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C.R.Lancaster,
A.Kröger,
M.Auer,
H.Michel.
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Ref.
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Nature, 1999,
402,
377-385.
[DOI no: ]
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PubMed id
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Abstract
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Fumarate reductase couples the reduction of fumarate to succinate to the
oxidation of quinol to quinone, in a reaction opposite to that catalysed by the
related complex II of the respiratory chain (succinate dehydrogenase). Here we
describe the crystal structure at 2.2 A resolution of the three protein subunits
containing fumarate reductase from the anaerobic bacterium Wolinella
succinogenes. Subunit A contains the site of fumarate reduction and a covalently
bound flavin adenine dinucleotide prosthetic group. Subunit B contains three
iron-sulphur centres. The menaquinol-oxidizing subunit C consists of five
membrane-spanning, primarily helical segments and binds two haem b molecules. On
the basis of the structure, we propose a pathway of electron transfer from the
dihaem cytochrome b to the site of fumarate reduction and a mechanism of
fumarate reduction. The relative orientations of the soluble and
membrane-embedded subunits of succinate:quinone oxidoreductases appear to be
unique.
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Figure 1.
Figure 1 Representative parts of the experimental
electron-density maps for crystal form A calculated with the
MIRAS phases after density modification and phase extension to
2.2 ? resolution. C, N, O, P and S atoms are shown in grey,
blue, red, light green and green, respectively; haem iron
centres are shown in orange. Contour levels are 1.0  (green)
and 9.0 (red)
above the mean density of the map. Figs 1-4 and 6 were prepared
with a version of Molscript46 modified by R. Esnouf for colour
ramping47 and map drawing48 capabilities. a, b, The two haem b
molecules (b[P] in the top half; b[D] in the bottom half of each
panel) and the side chains of some neighbouring residues in the
transmembrane region. c, The covalently bound FAD prosthetic
group.
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Figure 2.
Figure 2 The three-dimensional structure of fumarate
reductase. a, The fumarate reductase dimer viewed parallel to
the membrane. The polypeptide backbones of the two A subunits
are shown in blue and light blue, those of the two B subunits in
red and pink, and those of the C subunits in green and yellow.
Subunit A contains a covalently bound FAD. Subunit B contains
three iron-sulphur clusters (Fe[2]S[2], Fe[4]S[4] and
Fe[3]S[4]). The membrane-embedded subunit C contains two haem b
molecules. b, View of the transmembrane helices of the subunit C
dimer along the membrane normal from the cytoplasmic side. One
monomer is colour-coded from blue (N terminus) to yellow (C
terminus), the other from yellow (N terminus) to red (C
terminus)). The transmembrane helices are labelled I, II, IV, V
and VI (ref. 22). Secondary structures were assigned using
DSSP49. Figure rendered with Raster3D^50.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(1999,
402,
377-385)
copyright 1999.
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