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[[Image:1cpg.jpg|left|200px]]
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[[Image:1cpg.png|left|200px]]


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{{STRUCTURE_1cpg|  PDB=1cpg  |  SCENE=  }}  
{{STRUCTURE_1cpg|  PDB=1cpg  |  SCENE=  }}  


'''A CATION BINDING MOTIF STABILIZES THE COMPOUND I RADICAL OF CYTOCHROME C PEROXIDASE'''
===A CATION BINDING MOTIF STABILIZES THE COMPOUND I RADICAL OF CYTOCHROME C PEROXIDASE===




==Overview==
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Cytochrome c peroxidase reacts with peroxide to form compound I, which contains an oxyferryl heme and an indolyl radical at Trp-191. The indolyl free radical has a half-life of several hours at room temperature, and this remarkable stability is essential for the catalytic function of cytochrome c peroxidase. To probe the protein environment that stabilizes the compound I radical, we used site-directed mutagenesis to replace Trp-191 with Gly or Gln. Crystal structures of these mutants revealed a monovalent cation binding site in the cavity formerly occupied by the side chain of Trp-191. Comparison of this site with those found in other known cation binding enzymes shows that the Trp-191 side chain resides in a consensus K+ binding site. Electrostatic potential calculations indicate that the cation binding site is created by partial negative charges at the backbone carbonyl oxygen atoms of residues 175 and 177, the carboxyl end of a long alpha-helix (residues 165-175), the heme propionates, and the carboxylate side chain of Asp-235. These features create a negative potential that envelops the side chain of Trp-191; the calculated free energy change for cation binding in this site is -27 kcal/mol (1 cal = 4.184J). This is more than sufficient to account for the stability of the Trp-191 radical, which our estimates suggest is stabilized by 7.8 kcal/mol relative to a Trp radical in solution.
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{{ABSTRACT_PUBMED_7972020}}


==About this Structure==
==About this Structure==
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[[Category: Kraut, J.]]
[[Category: Kraut, J.]]
[[Category: Miller, M A.]]
[[Category: Miller, M A.]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May  2 12:58:40 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 21:03:37 2008''

Revision as of 18:03, 30 June 2008

File:1cpg.png

Template:STRUCTURE 1cpg

A CATION BINDING MOTIF STABILIZES THE COMPOUND I RADICAL OF CYTOCHROME C PEROXIDASE

Template:ABSTRACT PUBMED 7972020

About this Structure

1CPG is a Single protein structure of sequence from Saccharomyces cerevisiae. Full crystallographic information is available from OCA.

Reference

A cation binding motif stabilizes the compound I radical of cytochrome c peroxidase., Miller MA, Han GW, Kraut J, Proc Natl Acad Sci U S A. 1994 Nov 8;91(23):11118-22. PMID:7972020

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