1qd1
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(New page: 200px<br /><applet load="1qd1" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qd1, resolution 1.7Å" /> '''THE CRYSTAL STRUCTURE...)
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Revision as of 22:28, 20 November 2007
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THE CRYSTAL STRUCTURE OF THE FORMIMINOTRANSFERASE DOMAIN OF FORMIMINOTRANSFERASE-CYCLODEAMINASE.
Overview
BACKGROUND: The bifunctional enzyme formiminotransferase-cyclodeaminase, (FTCD) contains two active sites at different positions on the protein, structure. The enzyme binds a gamma-linked polyglutamylated form of the, tetrahydrofolate substrate and channels the product of the transferase, reaction from the transferase active site to the cyclodeaminase active, site. Structural studies of this bifunctional enzyme and its, monofunctional domains will provide insight into the mechanism of, substrate channeling and the two catalytic reactions. RESULTS: The crystal, structure of the formiminotransferase (FT) domain of FTCD has been, determined in the presence of a product analog, folinic acid. The overall, structure shows that the FT domain comprises two subdomains that adopt a, novel alpha/beta fold. Inspection of the folinic acid binding site reveals, an electrostatic tunnel traversing the width of the molecule. The, distribution of charged residues in the tunnel provides insight into the, possible mode of substrate binding and channeling. The electron density, reveals that the non-natural stereoisomer, (6R)-folinic acid, binds to the, protein; this observation suggests a mechanism for product release. In, addition, a single molecule of glycerol is bound to the enzyme and, indicates a putative binding site for formiminoglutamate. CONCLUSIONS: The, structure of the FT domain in the presence of folinic acid reveals a, possible novel mechanism for substrate channeling. The position of the, folinic acid and a bound glycerol molecule near to the sidechain of His82, suggests that this residue may act as the catalytic base required for the, formiminotransferase mechanism.
About this Structure
1QD1 is a Single protein structure of sequence from Sus scrofa with FON and GOL as ligands. Active as Glutamate formimidoyltransferase, with EC number 2.1.2.5 Full crystallographic information is available from OCA.
Reference
The crystal structure of the formiminotransferase domain of formiminotransferase-cyclodeaminase: implications for substrate channeling in a bifunctional enzyme., Kohls D, Sulea T, Purisima EO, MacKenzie RE, Vrielink A, Structure. 2000 Jan 15;8(1):35-46. PMID:10673422
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