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PDBsum entry 19hc
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Electron transport
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PDB id
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19hc
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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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The primary and three-Dimensional structures of a nine-Haem cytochrome c from desulfovibrio desulfuricans atcc 27774 reveal a new member of the hmc family.
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Authors
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P.M.Matias,
R.Coelho,
I.A.Pereira,
A.V.Coelho,
A.W.Thompson,
L.C.Sieker,
J.L.Gall,
M.A.Carrondo.
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Ref.
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Structure, 1999,
7,
119-130.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Haem-containing proteins are directly involved in electron transfer
as well as in enzymatic functions. The nine-haem cytochrome c (9Hcc), previously
described as having 12 haem groups, was isolated from cells of Desulfovibrio
desulfuricans ATCC 27774, grown under both nitrate- and sulphate-respiring
conditions. RESULTS: Models for the primary and three-dimensional structures of
this cytochrome, containing 292 amino acid residues and nine haem groups, were
derived using the multiple wavelength anomalous dispersion phasing method and
refined using 1.8 A diffraction data to an R value of 17.0%. The nine haem
groups are arranged into two tetrahaem clusters, with Fe-Fe distances and local
protein fold similar to tetrahaem cytochromes c3, while the extra haem is
located asymmetrically between the two clusters. CONCLUSIONS: This is the first
known three-dimensional structure in which multiple copies of a tetrahaem
cytochrome c3-like fold are present in the same polypeptide chain. Sequence
homology was found between this cytochrome and the C-terminal region (residues
229-514) of the high molecular weight cytochrome c from Desulfovibrio vulgaris
Hildenborough (DvH Hmc). A new haem arrangement in domains III and IV of DvH Hmc
hydrogenase from D. desulfuricans ATCC 27774, but that this reduction is faster
in the presence of tetrahaem cytochrome c3. As Hmc has never been found in D.
desulfuricans ATCC 27774, we propose that 9Hcc replaces it in this organism and
is therefore probably involved in electron transfer across the membrane.
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Figure 4.
Figure 4. Domain structure of 9Hcc from D. desulfuricans ATCC
27774, established on the basis of comparison with the known
structure of the tetrahaem cytochrome c[3] from the same
organism. The different domains of the structure are
colour-coded: the c[3]-like tetrahaem region of the N-terminal
domain is represented in yellow (residues 1–107 and
125–132); the insertion containing the isolated haem-binding
region is drawn in cyan (residues 108–124); the polypeptide
segment connecting the two domains is represented in green
(residues 133–176); the c[3]-like tetrahaem region of the
C-terminal domain is in red (residues 177–205 and 224–292);
and the insertion containing the second axial ligand of the
isolated haem is shown in purple (residues 206–223).
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1999,
7,
119-130)
copyright 1999.
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