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PDBsum entry 1ehk
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Oxidoreductase
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PDB id
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1ehk
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Contents |
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544 a.a.
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166 a.a.
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33 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 and mechanism of the aberrant ba(3)-Cytochrome c oxidase from thermus thermophilus.
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Authors
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T.Soulimane,
G.Buse,
G.P.Bourenkov,
H.D.Bartunik,
R.Huber,
M.E.Than.
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Ref.
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EMBO J, 2000,
19,
1766-1776.
[DOI no: ]
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PubMed id
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Abstract
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Cytochrome c oxidase is a respiratory enzyme catalysing the energy-conserving
reduction of molecular oxygen to water. The crystal structure of the
ba(3)-cytochrome c oxidase from Thermus thermophilus has been determined to 2.4
A resolution using multiple anomalous dispersion (MAD) phasing and led to the
discovery of a novel subunit IIa. A structure-based sequence alignment of this
phylogenetically very distant oxidase with the other structurally known
cytochrome oxidases leads to the identification of sequence motifs and residues
that seem to be indispensable for the function of the haem copper oxidases, e.g.
a new electron transfer pathway leading directly from Cu(A) to Cu(B). Specific
features of the ba(3)-oxidase include an extended oxygen input channel, which
leads directly to the active site, the presence of only one oxygen atom (O(2-),
OH(-) or H(2)O) as bridging ligand at the active site and the mainly hydrophobic
character of the interactions that stabilize the electron transfer complex
between this oxidase and its substrate cytochrome c. New aspects of the proton
pumping mechanism could be identified.
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Figure 2.
Figure 2 Stereo representation of the binuclear centre haem
a[s3] Cu[B] including the final 2F[obs] - F[calc] electron
density map contoured at 1.0  (blue).
Haem a[s3], the histidine ligands and the covalently linked
Tyr237 are shown as stick models in orange and green,
respectively. The covalent bond between Tyr237 and His233 is
well defined in the electron density. The F[obs] - F[calc]
difference electron density (contoured at 5.0 ,
green) between the haem a[s3] iron and Cu[B] (cyan) is of almost
spherical shape and is best interpreted as one oxygen atom
(O^2-, OH^- or H[2]O; purple), located equidistant between the
two metal atoms. This figure was prepared with MAIN (Turk, 1992).
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Figure 5.
Figure 5 Stereo representation of the electron transfer pathways
in the ba[3]-cytochrome c oxidase from T.thermophilus. The haems
b and a[s3] are shown in orange, the copper atoms in blue and
the metal-ligating amino acid residues in green. The two
arginine residues (Arg450 and Arg449) and Phe385, which are
involved in the electron transfer from Cu[A] via haem b to the
active site haem a[s3] Cu[B] are depicted in purple. The
residues that form the newly postulated electron transfer
pathway leading from Cu[A] to the aromatic ring system of Tyr136
and from there via a hydrogen bond and Trp229 to the Cu[B]
ligand His238 are represented in cyan, including the
corresponding distances. This figure was prepared with MAIN
(Turk, 1992).
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The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO J
(2000,
19,
1766-1776)
copyright 2000.
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