1K7F

1K7F is the Protein Data Bank (PDB) identification code for a protein structure. Specifically, it represents the crystal structure of the enzyme dihydrofolate reductase (DHFR) from the bacterium *Escherichia coli* in complex with the inhibitor methotrexate. DHFR is a crucial enzyme in the folate metabolic pathway, responsible for the reduction of dihydrofolate to tetrahydrofolate. Tetrahydrofolate is essential for the synthesis of purines, pyrimidines, and certain amino acids, making it vital for DNA replication and cell growth. Methotrexate is a potent inhibitor of DHFR and is widely used as a chemotherapeutic agent in the treatment of various cancers and autoimmune diseases. The 1K7F structure provides atomic-level detail about how methotrexate binds to the active site of *E. coli* DHFR, revealing key interactions between the inhibitor and the enzyme's amino acid residues. This information has been instrumental in understanding the mechanism of DHFR inhibition and in the design of new, more selective DHFR inhibitors. The resolution of the 1K7F structure is typically reported in the PDB entry and indicates the level of detail that can be discerned in the electron density map. Studying such structures helps researchers elucidate enzyme function, identify drug targets, and develop novel therapeutic strategies.