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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1os7
Original Entry
Title:
Oxidoreductase
Compound:
Crystal structure of taud with iron, alpha-ketoglutarate and t
bound at ph 7.5
Mutant:
No
UniProt/Swiss-Prot:
P37610-TAUD_ECOLI
EC Class:
1.14.11.17
Other CSA Entries:
Overview of all sites for 1os7
Homologues of 1os7
Entries for UniProt/Swiss-Prot: P37610
Entries for EC: 1.14.11.17
Other Databases:
PDB entry: 1os7
PDBsum entry: 1os7
UniProt/Swiss-Prot: P37610
IntEnz entry: 1.14.11.17
Literature Report:
Introduction:
Taurine:alpha-ketoglutarate dioxygenase (TauD) hydroxylates C1 of taurine
(2-aminoethane-1-sulfonic acid) and other organosulfates, leading to elimination of sulfite and thereby initiating the acquisition of sulphur from compounds that contain the element in a form that would otherwise be biologically inert. E. coli expresses TauD only in the absence of sulfate. The reaction requires molecular dioxygen and 2-oxoglutarate as a cosubstrate.
Mechanism:
1) In the resting state, Fe(II) is coordinated by His99, Asp 101, His 255 and three water molecules.

2) The cosubstrate 2-oxoglutarate binds to Fe(II) via the carbonyls on C1 and C2, displacing two water molecules. Taurine binds (not to Fe(II)), displacing the third water molecule.

3) Dioxygen binds to Fe(II) via one of the oxygen atoms; this formally oxidises iron to Fe(III).

4) The radical on the O-O bond attacks C2 of 2-oxoglutarate, with the C2
carbonyl attacking and oxidising iron to Fe(IV).

5) The cosubstrate is decarboxylated with C1 leaving as carbon dioxide. This is concomitant with heterolytic O-O bond cleavage and oxidation of the cosubstrate, giving an Fe(IV)=O oxoferryl intermediate with bound succinate.

6) The oxo atom abstracts the taurine C1 hydrogen in a radical mechanism, with reduction of iron to Fe(III)-OH, leaving a radical on taurine.

7) The taurine radical is hydroxylated with OH to give 1-hydroxytaurine, with reduction of iron to Fe(II), regenerating the initial oxidation state.

8) 1-hydroxytaurine decomposes to give sulfite and aminoacetaldehyde.

Arg 270 changes its hydrogen bonding to the cosubstrate during the reaction, and may initiate the decarboxylation step or help to remove carbon dioxide from the metal coordination sphere.
Sites:

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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ARGA 270 270Sidechain
ElectrostaticSubstrate
Arg 270 hydrogen bonds to the cosubstrate, and may initiate decarboxylation, or the leaving of carbon dioxide from the iron coordination sphere.
Evidence from paper Evidence concerns Evidence type
PubMed ID 15023059 Related protein: UniProt Q9WWU5 Residue is positioned appropriately (ligand position known)

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
FE2A 302 0
Radical formationSubstrate
The iron centre binds dioxygen and cosubstrate, facilitating the oxidative decarboxylation of the cosubstrate from oxoglutarate to succinate, and transfer of the hydroxy group from dioxygen to taurine.
Evidence from paper Evidence concerns Evidence type
PubMed ID 15924433 Current protein Residue is covalently bound to intermediate, based on non-structural data
PubMed ID 15924433 Current protein Ligand is essential for catalysis
Notes:
Ascorbate increases the reaction rate. The mechanism of this is not known, but has been proposed to be via the prevention of oxidative self-inactivation.
References:
1
Kinetic dissection of the catalytic mechanism of taurine:alpha-ketoglutarate dioxygenase (TauD) from Escherichia coli.
J. C. Price and E. W. Barr and L. M. Hoffart and C. Krebs and J. M. Bollinger
Biochemistry 44, (22) 8138-47, (2005).
15924433
2
Crystal structure of the alkylsulfatase AtsK: insights into the catalytic mechanism of the Fe(II) alpha-ketoglutarate-dependent dioxygenase superfamily.
I. Müller and A. Kahnert and T. Pape and G. M. Sheldrick and W. Meyer-Klaucke and T. Dierks and M. Kertesz and I. Usón
Biochemistry 43, (11) 3075-88, (2004).
15023059
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