PDBsum entry 2cd7

Hydrolase

PDB id: 2cd7

Contents

Protein chain

131 a.a. *

Metals

_NA

Waters ×164

* Residue conservation analysis

PDB id:

2cd7

Name:

Hydrolase

Title:

Staphylococcus aureus pi258 arsenate reductase (arsc) h62q mutant

Structure:

Protein arsc. Chain: a. Synonym: arsenate reductase, arsenical pump modifier, low molecular weight protein-tyrosine-phosphatase. Engineered: yes. Mutation: yes. Other_details: reduced

Source:

Staphylococcus aureus. Organism_taxid: 1280. Expressed in: escherichia coli. Expression_system_taxid: 511693.

Resolution:

1.50Å R-factor: 0.185 R-free: 0.218

Authors:

L.Buts,G.Roos,K.Van Belle,E.Brosens,R.Loris,L.Wyns,J.Messens

Key ref:

G.Roos et al. (2006). Interplay between ion binding and catalysis in the thioredoxin-coupled arsenate reductase family. J Mol Biol, 360, 826-838. PubMed id: 16797027 DOI: 10.1016/j.jmb.2006.05.054

Date:

23-Jan-06 Release date: 28-Jun-06

Protein chain

P0A006  (ARSC_STAAU) -  Arsenate reductase from Staphylococcus aureus

Seq: 131 a.a.

Struc: 131 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.1.20.4.4 - arsenate reductase (thioredoxin).
• Reaction: arsenate + [thioredoxin]-dithiol + H⁺ = arsenite + [thioredoxin]- disulfide + H2O

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

DOI no: 10.1016/j.jmb.2006.05.054

J Mol Biol 360:826-838 (2006)

PubMed id: 16797027

Interplay between ion binding and catalysis in the thioredoxin-coupled arsenate reductase family.

G.Roos, L.Buts, K.Van Belle, E.Brosens, P.Geerlings, R.Loris, L.Wyns, J.Messens.

ABSTRACT

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.

Selected figure(s)

Figure 2.
Figure 2. Stereo view of the refined structure of Bs_ArsC. Lysine 33 (blue), aspartate 30 and glutamate 31 (red), the P-loop active site (residues 10–16) (red tube) with asparagine 13 (red stick representation), the redox-active cysteine residues (yellow), sulphate (atom type), the cation-binding site residues (green) and sodium (magenta) are shown. The Figure was generated by using MacPyMol (Delano Scientific LLC 2005).

Figure 6.
Figure 6. The conformational change in the P-loop of Sa_ArsC (a) The 2F[o]–F[c] electron density map contoured at 1σ of the P-loop of Sa_ArsC C10SC15A (PDB code 2FXI). (b) The P-loop active site of Sa_ArsC C10SC15A harbouring a sulphate molecule (PDB code 2FXI) (green) with the peptide bond between Gly12 and Asn13 in a left-handed α[L] conformation. On top is the P-loop (PDB code 1JFV)^8 (salmon) that binds a perchlorate (not shown) with the peptide bond between Gly12 and Asn13 flipped to a β conformation is visualized. Structures were superposed with the SSM algorithm.^21 Figures were generated by using MacPyMol (Delano Scientific LLC 2005).

The above figures are reprinted by permission from Elsevier: J Mol Biol (2006, 360, 826-838) copyright 2006.

Figures were selected by an automated process.