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PDBsum entry 1bcc
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Oxidoreductase
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PDB id
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1bcc
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Contents |
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442 a.a.
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406 a.a.
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379 a.a.
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241 a.a.
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196 a.a.
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100 a.a.
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78 a.a.
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66 a.a.
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33 a.a.
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59 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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Electron transfer by domain movement in cytochrome bc1.
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Authors
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Z.Zhang,
L.Huang,
V.M.Shulmeister,
Y.I.Chi,
K.K.Kim,
L.W.Hung,
A.R.Crofts,
E.A.Berry,
S.H.Kim.
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Ref.
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Nature, 1998,
392,
677-684.
[DOI no: ]
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PubMed id
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Abstract
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The cytochrome bc1 is one of the three major respiratory enzyme complexes
residing in the inner mitochondrial membrane. Cytochrome bc1 transfers electrons
from ubiquinol to cytochrome c and uses the energy thus released to form an
electrochemical gradient across the inner membrane. Our X-ray crystal structures
of the complex from chicken, cow and rabbit in both the presence and absence of
inhibitors of quinone oxidation, reveal two different locations for the
extrinsic domain of one component of the enzyme, an iron-sulphur protein. One
location is close enough to the supposed quinol oxidation site to allow
reduction of the Fe-S protein by ubiquinol. The other site is close enough to
cytochrome c1 to allow oxidation of the Fe-S protein by the cytochrome. As
neither location will allow both reactions to proceed at a suitable rate, the
reaction mechanism must involve movement of the extrinsic domain of the Fe-S
component in order to shuttle electrons from ubiquinol to cytochrome c1. Such a
mechanism has not previously been observed in redox protein complexes.
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Figure 3.
Figure 3 Structure of the intermembrane (external surface)
domains of the chicken bc[1] complex. This is viewed from within
the membrane, with the transmembrane helices truncated at
roughly the membrane surface. Ball-and-stick models represent
the haem group of cytochrome c[1], the Rieske iron-sulphur
cluster, and the disulphide cysteines of subunit 8. SU, subunit;
cyt, cytochrome.
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Figure 6.
Figure 6 Relative positions of the redox centres in the two
different conformations of the bc[1] complex dimer. a, b, Iron
centres revealed by anomalous scattering near the iron edge. The
net is a Bivoet difference map with X-ray wavelength 7,131 eV
phased with experimental phases improved by averaging, and
contoured at 4.5  .
c, d, Schematic drawing representing the cofactors. a, c,
Results from a native crystal, with the iron-sulphur cluster of
the Rieske protein in the distal position (from the
low-potential haem group of cytochrome b). b, d, Results from a
crystal containing bound stigmatellin, with the cluster in the
proximal position.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(1998,
392,
677-684)
copyright 1998.
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