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Dihydrofolate Reductase
Exploring the Structure
The drug methotrexate is designed to mimic a folate molecule, so that it will bind in the active site of the enzyme and block its action. Methotrexate is about the same size as folate, with similar chemical composition. In these two early crystal structures, PDB entries 7dfr and 3dfr, researchers confirmed that the drug does in fact mimic folate, binding in a very similar position. In these pictures, the carbon atoms in NADPH are colored green, and carbon atoms in the drug are white. Notice how the nicotinamide ring at the lower end of the nucleotide packs tightly against flat rings of methotrexate and folate. During the chemical reaction, hydrogen atoms (which are unfortunately not seen in crystal structures) are transferred from the nicotinamide to these large, flat rings.Dihydrofolate reductase has been the focus of intense research for many years, so many other structures of dihydrofolate reductase with a variety of substrates and drugs are available at the PDB. As you browse through these structures, notice the many different approaches that researchers have taken to blocking this small, but important, enzyme.
These illustrations were created with RasMol. You can create similar pictures by clicking on the accession codes above and picking one of the options under View Structure.
A list of all dihydrofolate reductase structures in the PDB as of October, 2002, is available here.
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Last changed by: A.Honegger,