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From Proteopedia
Crystal structure of the di-haem cytochrome c peroxidase from Pseudomonas aeruginosa
Structural highlights
Function[CCPR_PSEAE] Catalyzes the peroxidative oxidation of azurin and cytochrome c551. Likely to provide protection against toxic peroxides. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: 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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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