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1eb7

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==Overview==
==Overview==
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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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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.
==About this Structure==
==About this Structure==
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[[Category: peroxidase]]
[[Category: peroxidase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb 3 09:38:58 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:25:56 2008''

Revision as of 10:25, 21 February 2008

Image:1eb7.jpg

1eb7, resolution 2.4Å

Drag the structure with the mouse to rotate

CRYSTAL STRUCTURE OF THE DI-HAEM CYTOCHROME C PEROXIDASE FROM PSEUDOMONAS AERUGINOSA

Overview

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.

About this Structure

1EB7 is a Single protein structure of sequence from Pseudomonas aeruginosa with and as ligands. Active as Cytochrome-c peroxidase, with EC number 1.11.1.5 Known structural/functional Sites: , and . Full crystallographic information is available from OCA.

Reference

Crystal structure of the di-haem cytochrome c peroxidase from Pseudomonas aeruginosa., Fulop V, Ridout CJ, Greenwood C, Hajdu J, Structure. 1995 Nov 15;3(11):1225-33. PMID:8591033

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