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PDBsum entry 1eb7
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Oxidoreductase
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PDB id
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1eb7
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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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Crystal structure of the di-Haem cytochrome c peroxidase from pseudomonas aeruginosa.
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Authors
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V.Fülöp,
C.J.Ridout,
C.Greenwood,
J.Hajdu.
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Ref.
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Structure, 1995,
3,
1225-1233.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Cytochrome c peroxidase from Pseudomonas aeruginosa (PsCCP)
represents a new class of peroxidases which work without the need to create a
semi-stable free radical for catalysis. The enzyme is located in the bacterial
periplasm where its likely function is to provide protection against toxic
peroxides. The soluble 323-residue single polypeptide chain contains two
covalent c-type haems with very different properties: one of them is a
low-potential (-330 mV) centre where hydrogen peroxide is reduced (the
peroxidatic site); the other is a high-potential (+320 mV) centre which feeds
electrons to the peroxidatic site from soluble electron-shuttle proteins such as
cytochrome c and azurin. RESULTS: The crystal structure of the oxidized form of
PsCCP has been determined to 2.4 A resolution by multiple isomorphous
replacement, and refined to an R-factor of 19.2%. PsCCP is organized into two
domains, both of them containing a covalent c-haem in a structure reminiscent of
class 1 cytochromes c. The domains are related by a quasi-twofold axis. The
domain interface holds a newly discovered calcium-binding site with an unusual
set of ligands. CONCLUSIONS: The likely function of the calcium site is to
maintain the structural integrity of the enzyme and/or to modulate electron
transfer between the two haem domains. The low-potential haem has two histidine
axial ligands (His55 and His71) and the high-potential haem is ligated by His201
and Met275. There are no polar residues at the peroxidatic site in the inactive
oxidized enzyme. The structure suggests that, in the half-reduced functional
form of the enzyme, the low-potential haem has to shed His71 in order to make
the enzyme catalytically competent. This process is likely to trigger a
reorganization of the active site, and may introduce a new residues into the
haem pocket.
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Figure 3.
Figure 3. The structure of cytochrome c peroxidase from P.
aeruginosa. The ribbon diagram is colour-ramped blue to red from
the N to the C terminus. The small grey sphere shows the
location of the calcium ion and the haems are in ball-and-stick
representation. LP and HP denote low-potential and
high-potential haem domains, respectively. Figure 3. The
structure of cytochrome c peroxidase from P. aeruginosa. The
ribbon diagram is colour-ramped blue to red from the N to the C
terminus. The small grey sphere shows the location of the
calcium ion and the haems are in ball-and-stick representation.
LP and HP denote low-potential and high-potential haem domains,
respectively.
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Figure 5.
Figure 5. Comparison of the fold of the c-type cytochrome
domains of PsCCP with the fold of typical class 1 cytochromes c.
(a) High-potential haem domain of PsCCP. (b) Low-potential haem
domain of PsCCP. (c) Cytochrome c[551] from P. aeruginosa (PDB
[23] entry 351C). (d) Tuna cytochrome c (PDB entry 3CYT).
The cytochromes are colour-ramped dark blue to light blue from
the N to the C terminus. The PsCCP domains are coloured
similarly. The haems are shown in ball-and-stick representation.
Figure 5. Comparison of the fold of the c-type cytochrome
domains of PsCCP with the fold of typical class 1 cytochromes c.
(a) High-potential haem domain of PsCCP. (b) Low-potential haem
domain of PsCCP. (c) Cytochrome c[551] from P. aeruginosa (PDB
[[6]23] entry 351C). (d) Tuna cytochrome c (PDB entry 3CYT). The
cytochromes are colour-ramped dark blue to light blue from the N
to the C terminus. The PsCCP domains are coloured similarly. The
haems are shown in ball-and-stick representation.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(1995,
3,
1225-1233)
copyright 1995.
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