when the cytosol was subjected to gel filtration , two immunoreactive proteins were separated , a high-molecular-weight ( mr 318,000 ) protein which did not have catalytic activity and which did not bind [ 3h ] methotrexate and a smaller protein ( mr approximately 20,000 ) which did reduce [ 3h ] folic acid to tetrahydrofolate and did bind [ 3h ] methotrexate .
C0016410
folic acid
C0025677
methotrexate