The structure of mouse L1210 dihydrofolate reductase‐drug complexes and the construction of a model of human enzyme

Abstract
The structure of mouse L1210 dihydrofolate reductase (DHFR) complexed with NADPH and trimethoprim has been refined at 2.0 Å resolution. The analogous complex with NADPH and methotrexate has been refined at 2.5 Å resolution. These structures reveal for the first time details of drug interactions with a mammalian DHFR, which are compared with those observed from previous X‐ray investigations of DHFR/inhibitor complexes. The refined L1210 structure has been used as the basis for the construction of a model of the human enzyme. There are only twenty‐one sequence differences between mouse L1210 and human DHFRs, and all but two of these are located close to the molecular surface: a strong indication that the active sites are essentially identical in these two mammalian enzymes.