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Title
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Crystal structures of recombinant human dihydrofolate reductase complexed with folate and 5-deazafolate.
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Authors
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J.F.Davies,
T.J.Delcamp,
N.J.Prendergast,
V.A.Ashford,
J.H.Freisheim,
J.Kraut.
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Ref.
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Biochemistry, 1990,
29,
9467-9479.
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PubMed id
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Abstract
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The 2.3-A crystal structure of recombinant human dihydrofolate reductase (EC
1.5.1.3, DHFR) has been solved as a binary complex with folate (a poor substrate
at neutral pH) and also as a binary complex with an inhibitor, 5-deazafolate.
The inhibitor appears to be protonated at N8 on binding, whereas folate is not.
Rotation of the peptide plane joining I7 and V8 from its position in the folate
complex permits hydrogen bonding of 5-deazafolate's protonated N8 to the
backbone carbonyl of I7, thus contributing to the enzyme's greater affinity for
5-deazafolate than for folate. In this respect it is likely that bound
5-deazafolate furnishes a model for 7,8-dihydrofolate binding and, in addition,
resembles the transition state for folate reduction. A hypothetical
transition-state model for folate reduction, generated by superposition of the
DHFR binary complexes human.5-deazafolate and chicken liver.NADPH, reveals a 1-A
overlap of the binding sites for folate's pteridine ring and the
dihydronicotinamide ring of NADPH. It is proposed that this binding-site overlap
accelerates the reduction of both folate and 7,8-dihydrofolate by simultaneously
binding substrate and cofactor with a sub van der Waals separation that is
optimal for hydride transfer.
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