1cck
From Proteopedia
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'''ALTERING SUBSTRATE SPECIFICITY OF CYTOCHROME C PEROXIDASE TOWARDS A SMALL MOLECULAR SUBSTRATE PEROXIDASE BY SUBSTITUTING TYROSINE FOR PHE 202''' | '''ALTERING SUBSTRATE SPECIFICITY OF CYTOCHROME C PEROXIDASE TOWARDS A SMALL MOLECULAR SUBSTRATE PEROXIDASE BY SUBSTITUTING TYROSINE FOR PHE 202''' | ||
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[[Category: Musah, R A.]] | [[Category: Musah, R A.]] | ||
[[Category: Wilcox, S K.]] | [[Category: Wilcox, S K.]] | ||
| - | [[Category: | + | [[Category: Oxidoreductase]] |
| - | [[Category: | + | [[Category: Peroxidase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:35:01 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 09:35, 2 May 2008
ALTERING SUBSTRATE SPECIFICITY OF CYTOCHROME C PEROXIDASE TOWARDS A SMALL MOLECULAR SUBSTRATE PEROXIDASE BY SUBSTITUTING TYROSINE FOR PHE 202
Overview
The crystal structure of recombinant pea cytosolic ascorbate peroxidase has been refined to an R = 0.19 for data between 8.0 and 2.2 A resolution and magnitude of F > or = 2 sigma(magnitude of F). The refined model consists of four ascorbate peroxidase monomers consisting of 249 residues per monomer assembled into two homodimers, with one heme group per monomer. The ascorbate peroxidase model confirms that the pea cytosolic enzyme is a noncovalent homodimer held together by a series of ionic interactions arranged around the 2-fold noncrystallographic dimer axis. As expected from the high level of sequence identity (33%), the overall fold of the ascorbate peroxidase monomer closely resembles that of cytochrome c peroxidase. The average root mean square differences for 137 helical alpha-carbon atoms between the four ascorbate peroxidase monomers and cytochrome c peroxidase and for 249 topologically equivalent alpha-carbon atoms are 0.9 and 1.3 A, respectively. The active site structures are also the same, including the hydrogen-bonding interactions between the proximal His ligand, a buried Asp residue, and a Trp residue, whose indole ring is parallel to and in contact with the proximal His ligand just under the heme ring. This proximal Trp residue is thought to be the site of free radical formation in cytochrome c peroxidase compound I and is also essential for enzyme activity. The corresponding Trp in ascorbate peroxidase, Trp179, occupies exactly the same position. The most interesting, and possibly functionally important, difference between the two peroxidases is the presence of a cation binding site in ascorbate peroxidase located approximately 8 A from the alpha-carbon atom of Trp179.
About this Structure
1CCK is a Single protein structure of sequence from Saccharomyces cerevisiae. Full crystallographic information is available from OCA.
Reference
Crystal structure of recombinant pea cytosolic ascorbate peroxidase., Patterson WR, Poulos TL, Biochemistry. 1995 Apr 4;34(13):4331-41. PMID:7703247 Page seeded by OCA on Fri May 2 12:35:01 2008
