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Direct 19 F NMR observation of the conformational selection of optically active rotamers of the antifolate compound fluoronitropyrimethamine bound to the enzyme dihydrofolate reductase
Author(s) -
Tendler Saul J.B.,
Griffin Roger J.,
Birdsall Berry,
Stevens Malcolm F.G.,
Roberts Gordon C.K.,
Feeney James
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80368-5
Subject(s) - conformational isomerism , dihydrofolate reductase , stereochemistry , chemistry , nuclear magnetic resonance spectroscopy , lactobacillus casei , ligand (biochemistry) , active site , molecular model , enzyme , crystallography , molecule , biochemistry , organic chemistry , receptor , fermentation
The molecular basis of the binding of the lipophilic antifolate compound fluoronitropyrimethamine [2,4‐diamino‐5‐(4‐fluoro‐3‐nitrophenyl)‐6‐ethylpyrimidine] to its target enzyme dihydrofolate reductase has been investigated using a combination of 19 F NMR spectroscopy and molecular mechanical calculations. 19 F NMR reveals the presence of two different conformational states for the fluoronitropyrimethamine‐ Lactobacillus casei enzyme complex. MM2 molecular mechanical calculations predict restricted rotation about the C5‐C1′ bond of the ligand and this gives rise to two slowly interconverting rotamers which are an enantiomeric pair. The results of 19 F NMR spectroscopy reveal that both these isomers bind to the enzyme, with different affinities. There is no detectable interconversion of the bound rotamers themselves on the NMR timescale. The effect of the addition of co‐enzyme to the sample is to reverse the preference the enzyme has for each rotamer.