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5ccp

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[[Image:5ccp.gif|left|200px]]
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{{STRUCTURE_5ccp| PDB=5ccp | SCENE= }}
{{STRUCTURE_5ccp| PDB=5ccp | SCENE= }}
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'''HISTIDINE 52 IS A CRITICAL RESIDUE FOR RAPID FORMATION OF CYTOCHROME C PEROXIDASE COMPOUND I'''
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===HISTIDINE 52 IS A CRITICAL RESIDUE FOR RAPID FORMATION OF CYTOCHROME C PEROXIDASE COMPOUND I===
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==Overview==
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The crystal structure and reactivity with hydrogen peroxide are reported for a mutant of a cloned cytochrome c peroxidase [CcP(MI)], in which the conserved distal His (His-52) is replaced with Leu. The reaction of the H52L enzyme with peroxide was examined as a function of pH in 0.1 M phosphate buffers and buffers in which nitrate was used to adjust the ionic strength. The pH-independent bimolecular rate constant for the reaction of H52L with peroxide was 731 +/- 44 and 236 +/- 14 M-1 s-1 in phosphate and nitrate-containing buffers, respectively. This represents a 10(5)-fold decrease in rate relative to the CcP(MI) parent under comparable conditions. Single-crystal diffraction studies showed that no dramatic changes in the structure or in the accessibility of the heme binding site were caused by the mutation. Rather, the mutation caused significant structural changes only at residue 52 and the nearby active-site water molecules. The residual reactivity of the H52L enzyme with peroxide was pH- and buffer-dependent. In nitrate-containing buffer, the apparent bimolecular rate constant for the reaction with peroxide decreased with decreasing pH; the loss of reactivity correlated with protonation of a group with an apparent pKA = 4.5. Protonation of the group caused a loss of reactivity with peroxide. This is in contrast to the CcP(MI) parent enzyme, as well as all other mutants that have been examined, where the loss of reactivity correlates with protonation of an enzyme group with an apparent pKA = 5.4.(ABSTRACT TRUNCATED AT 250 WORDS)
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(as it appears on PubMed at http://www.pubmed.gov), where 8396972 is the PubMed ID number.
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{{ABSTRACT_PUBMED_8396972}}
==About this Structure==
==About this Structure==
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[[Category: Miller, M A.]]
[[Category: Miller, M A.]]
[[Category: Shaw, A.]]
[[Category: Shaw, A.]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 22:32:30 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Jul 3 13:57:45 2008''

Revision as of 10:57, 3 July 2008

Image:5ccp.png

Template:STRUCTURE 5ccp

HISTIDINE 52 IS A CRITICAL RESIDUE FOR RAPID FORMATION OF CYTOCHROME C PEROXIDASE COMPOUND I

Template:ABSTRACT PUBMED 8396972

About this Structure

5CCP is a Single protein structure of sequence from Saccharomyces cerevisiae. Full crystallographic information is available from OCA.

Reference

Histidine 52 is a critical residue for rapid formation of cytochrome c peroxidase compound I., Erman JE, Vitello LB, Miller MA, Shaw A, Brown KA, Kraut J, Biochemistry. 1993 Sep 21;32(37):9798-806. PMID:8396972

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