Electrostatic forces in the inhibition of dihydrofolate reductase by methotrexate. A field potential study

Methotrexate (MTX) is a high affinity inhibitor of the reaction catalyzed by dihydrofolate reductase (DHFR) from Lactobacillus casei. MTX is a folic acid analogue, being effective in the treatment of neoplastic disease in humans. In order to understand the mechanism of its inhibition from an electrostatic point of view, we calculated electrostatic potentials originating from MTX, NADPH (co-factor)-DHFR complex, NADPH and DHFR, individually. The mutual relationships between MTX and DHFR-NADPH and between NADPH and DHFR were then visualized and compared with the simultaneous geometrical analysis, using a raster computer graphic technique. Complete complementalities of the electrostatic potential and the field electrostatic potential are communicated between MTX and the NADPH-DHFR complex and between NADPH and DHFR.