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2cd7

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[[Image:2cd7.gif|left|200px]]
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{{STRUCTURE_2cd7| PDB=2cd7 | SCENE= }}
{{STRUCTURE_2cd7| PDB=2cd7 | SCENE= }}
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'''STAPHYLOCOCCUS AUREUS PI258 ARSENATE REDUCTASE (ARSC) H62Q MUTANT'''
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===STAPHYLOCOCCUS AUREUS PI258 ARSENATE REDUCTASE (ARSC) H62Q MUTANT===
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==Overview==
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In the thioredoxin (Trx)-coupled arsenate reductase family, arsenate reductase from Staphylococcus aureus plasmid pI258 (Sa_ArsC) and from Bacillus subtilis (Bs_ArsC) are structurally related detoxification enzymes. Catalysis of the reduction of arsenate to arsenite involves a P-loop (Cys10Thr11Gly12Asn13Ser14Cys15Arg16) structural motif and a disulphide cascade between three conserved cysteine residues (Cys10, Cys82 and Cys89). For its activity, Sa_ArsC benefits from the binding of tetrahedral oxyanions in the P-loop active site and from the binding of potassium in a specific cation-binding site. In contrast, the steady-state kinetic parameters of Bs_ArsC are not affected by sulphate or potassium. The commonly occurring mutation of a histidine (H62), located about 6 A from the potassium-binding site in Sa_ArsC, to a glutamine uncouples the kinetic dependency on potassium. In addition, the binding affinity for potassium is affected by the presence of a lysine (K33) or an aspartic acid (D33) in combination with two negative charges (D30 and E31) on the surface of Trx-coupled arsenate reductases. In the P-loop of the Trx-coupled arsenate reductase family, the peptide bond between Gly12 and Asn13 can adopt two distinct conformations. The unique geometry of the P-loop with Asn13 in beta conformation, which is not observed in structurally related LMW PTPases, is stabilized by tetrahedral oxyanions and decreases the pK(a) value of Cys10 and Cys82. Tetrahedral oxyanions stabilize the P-loop in its catalytically most active form, which might explain the observed increase in k(cat) value for Sa_ArsC. Therefore, a subtle interplay of potassium and sulphate dictates the kinetics of Trx-coupled arsenate reductases.
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{{ABSTRACT_PUBMED_16797027}}
==About this Structure==
==About this Structure==
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[[Category: Ptpase i fold]]
[[Category: Ptpase i fold]]
[[Category: Redox-active center]]
[[Category: Redox-active center]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 21:51:40 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 15:09:20 2008''

Revision as of 12:09, 28 July 2008

Image:2cd7.png

Template:STRUCTURE 2cd7

STAPHYLOCOCCUS AUREUS PI258 ARSENATE REDUCTASE (ARSC) H62Q MUTANT

Template:ABSTRACT PUBMED 16797027

About this Structure

2CD7 is a Single protein structure of sequence from Staphylococcus aureus. Full crystallographic information is available from OCA.

Reference

Interplay between ion binding and catalysis in the thioredoxin-coupled arsenate reductase family., Roos G, Buts L, Van Belle K, Brosens E, Geerlings P, Loris R, Wyns L, Messens J, J Mol Biol. 2006 Jul 21;360(4):826-38. Epub 2006 Jun 6. PMID:16797027

Page seeded by OCA on Mon Jul 28 15:09:20 2008

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