A 50 year old lady is given methotrexate for severe rheumatoid disease causing joint pains and functional limitation. She also has to be given folinic rescue therapy. Which of the following is the mechanism by which methotrexate acts?: (A) Increasing folic acid excretion, (B) DNA binding, (C) Binding to dihydrofolate reductase, (D) Increasing nucleotide synthesis
Answer is C. Binding to dihydrofolate reductase