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PDBsum entry 2v6t
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References listed in PDB file
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Key reference
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Title
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Crystal structures of toxoplasma gondii pterin-4a-Carbinolamine dehydratase and comparisons with mammalian and parasite orthologues.
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Authors
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S.Cameron,
S.A.Fyffe,
S.Goldie,
W.N.Hunter.
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Ref.
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Mol Biochem Parasitol, 2008,
158,
131-138.
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PubMed id
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Abstract
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The enzyme pterin-4a-carbinolamine dehydratase (PCD) is important for the
recycling of pterins within eukaryotic cells. A recombinant expression system
for PCD from the apicomplexan parasite Toxoplasma gondii has been prepared, the
protein purified and crystallised. Single crystal X-ray diffraction methods have
produced a high-resolution structure (1.6A) of the apo-enzyme and a
low-resolution structure (3.1A) of a complex with a substrate-like ligand
dihydrobiopterin (BH(2)). Analysis of the hydrogen bonding interactions that
contribute to binding BH(2) suggest that the ligand is present in an enol
tautomeric state, which makes it more similar to the physiological substrate.
The enzyme can process (R)- and (S)-forms of pterin-4a-carbinolamine and the
ligand complex suggests that His61 and His79 are placed to act independently as
general bases for catalysis of the individual enantiomers. Comparisons with
orthologues from other protozoan parasites (Plasmodium falciparum and Leishmania
major) and with rat PCD, for which the structure is known, indicate a high
degree of sequence and structure conservation of this enzyme. The molecular
determinants of ligand recognition and PCD reactivity are therefore highly
conserved across species.
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