PDBsum entry 2a9c

Oxidoreductase

PDB id: 2a9c

Contents

Protein chains

359 a.a. *

Ligands

SO4 ×2

MTE ×2

GOL

Metals

_MO ×2

Waters ×532

* Residue conservation analysis

PDB id:

2a9c

Name:

Oxidoreductase

Title:

Crystal structure of r138q mutant of recombinant chicken sulfite oxidase with the bound product, sulfate, at the active site

Structure:

Sulfite oxidase. Chain: a, b. Fragment: catalytic core domain and c terminal dimerization domain. Engineered: yes. Mutation: yes

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Organ: liver. Organelle: mitochondrion. Cellular_location: mitochondrial intermembrane space. Gene: suox. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

2.51Å R-factor: 0.160 R-free: 0.237

Authors:

E.Karakas,H.L.Wilson,T.N.Graf,S.Xiang,S.Jaramillo-Busquets, K.V.Rajagopalan,C.Kisker

Key ref:

E.Karakas et al. (2005). Structural insights into sulfite oxidase deficiency. J Biol Chem, 280, 33506-33515. PubMed id: 16048997 DOI: 10.1074/jbc.M505035200

Date:

11-Jul-05 Release date: 02-Aug-05

Protein chains

P07850  (SUOX_CHICK) -  Sulfite oxidase from Gallus gallus

Seq: 459 a.a.

Struc: 359 a.a.*

* PDB and UniProt seqs differ at 7 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.1.8.3.1 - sulfite oxidase.
• Reaction: sulfite + O2 + H2O = sulfate + H2O2

sulfite + O2 + H2O = sulfate + H2O2 (Bound ligand (Het Group name = SO4) corresponds exactly)

• Cofactor: Heme; Mo cation

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

reference

DOI no: 10.1074/jbc.M505035200

J Biol Chem 280:33506-33515 (2005)

PubMed id: 16048997

Structural insights into sulfite oxidase deficiency.

E.Karakas, H.L.Wilson, T.N.Graf, S.Xiang, S.Jaramillo-Busquets, K.V.Rajagopalan, C.Kisker.

ABSTRACT

Sulfite oxidase deficiency is a lethal genetic disease that results from defects either in the genes encoding proteins involved in molybdenum cofactor biosynthesis or in the sulfite oxidase gene itself. Several point mutations in the sulfite oxidase gene have been identified from patients suffering from this disease worldwide. Although detailed biochemical analyses have been carried out on these mutations, no structural data could be obtained because of problems in crystallizing recombinant human and rat sulfite oxidases and the failure to clone the chicken sulfite oxidase gene. We synthesized the gene for chicken sulfite oxidase de novo, working backward from the amino acid sequence of the native chicken liver enzyme by PCR amplification of a series of 72 overlapping primers. The recombinant protein displayed the characteristic absorption spectrum of sulfite oxidase and exhibited steady state and rapid kinetic parameters comparable with those of the tissue-derived enzyme. We solved the crystal structures of the wild type and the sulfite oxidase deficiency-causing R138Q (R160Q in humans) variant of recombinant chicken sulfite oxidase in the resting and sulfate-bound forms. Significant alterations in the substrate-binding pocket were detected in the structure of the mutant, and a comparison between the wild type and mutant protein revealed that the active site residue Arg-450 adopts different conformations in the presence and absence of bound sulfate. The size of the binding pocket is thereby considerably reduced, and its position relative to the cofactor is shifted, causing an increase in the distance of the sulfur atom of the bound sulfate to the molybdenum.

Selected figure(s)

Figure 4.
FIGURE 4. Superposition of the active sites of the sulfate bound (yellow) and unbound rCSO (gray). Only the Moco of the sulfate free structure is shown. The molybdenum is shown in green, and the water/hydroxo ligand is shown as a red sphere. Hydrogen bonds between the sulfate and Arg-450 are shown with dashed lines.

Figure 8.
FIGURE 8. Proposed reaction mechanism for sulfite oxidase. Schematic presentation of the reaction mechanism for the oxidation of sulfite to sulfate. A, oxidized Mo center. B, the Mo(IV)-sulfate adduct formed after an attack of sulfite on the equatorial oxo group. C, the free reduced Mo(IV) center after release of sulfate.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2005, 280, 33506-33515) copyright 2005.

Figures were selected by an automated process.