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2c9x

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[[Image:2c9x.gif|left|200px]]
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{{STRUCTURE_2c9x| PDB=2c9x | SCENE= }}
{{STRUCTURE_2c9x| PDB=2c9x | SCENE= }}
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'''SULFITE DEHYDROGENASE FROM STARKEYA NOVELLA Y236F MUTANT'''
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===SULFITE DEHYDROGENASE FROM STARKEYA NOVELLA Y236F MUTANT===
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==Overview==
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The sulfite dehydrogenase from Starkeya novella is the only known sulfite-oxidizing enzyme that forms a permanent heterodimeric complex between a molybdenum and a heme c-containing subunit and can be crystallized in an electron transfer competent conformation. Tyr236 is a highly conserved active site residue in sulfite oxidoreductases and has been shown to interact with a nearby arginine and a molybdenum-oxo ligand that is involved in catalysis. We have created a Tyr236 to Phe substitution in the SorAB sulfite dehydrogenase. The purified SDH(Y236F) protein has been characterized in terms of activity, structure, intramolecular electron transfer, and EPR properties. The substituted protein exhibited reduced turnover rates and substrate affinity as well as an altered reactivity toward molecular oxygen as an electron acceptor. Following reduction by sulfite and unlike SDH(WT), the substituted enzyme was reoxidized quickly in the presence of molecular oxygen, a process reminiscent of the reactions of the sulfite oxidases. SDH(Y236F) also exhibited the pH-dependent CW-EPR signals that are typically observed in vertebrate sulfite oxidases, allowing a direct link of CW-EPR properties to changes caused by a single-amino acid substitution. No quantifiable electron transfer was seen in laser flash photolysis experiments with SDH(Y236F). The crystal structure of SDH(Y236F) clearly shows that as a result of the substitution the hydrogen bonding network surrounding the active site is disturbed, resulting in an increased mobility of the nearby arginine. These disruptions underline the importance of Tyr236 for the integrity of the substrate binding site and the optimal alignment of Arg55, which appears to be necessary for efficient electron transfer.
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{{ABSTRACT_PUBMED_16893171}}
==About this Structure==
==About this Structure==
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[[Category: Oxidoreductase]]
[[Category: Oxidoreductase]]
[[Category: Sulfite oxidase]]
[[Category: Sulfite oxidase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 13:11:51 2008''

Revision as of 10:11, 27 July 2008

Image:2c9x.png

Template:STRUCTURE 2c9x

SULFITE DEHYDROGENASE FROM STARKEYA NOVELLA Y236F MUTANT

Template:ABSTRACT PUBMED 16893171

About this Structure

2C9X is a Protein complex structure of sequences from Starkeya novella. Full crystallographic information is available from OCA.

Reference

Kinetic and structural evidence for the importance of Tyr236 for the integrity of the Mo active site in a bacterial sulfite dehydrogenase., Kappler U, Bailey S, Feng C, Honeychurch MJ, Hanson GR, Bernhardt PV, Tollin G, Enemark JH, Biochemistry. 2006 Aug 15;45(32):9696-705. PMID:16893171

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