Figure 2
Crystal structures of bifunctional homodimeric dihydrofolate reductase-thymidylate synthase from B. bovis (BbDHFR-TS). The DHFR subunit of each protomer (green, pink) is connected to a C-terminal TS subunit (violet, yellow) by a 40-residue linker (cyan, gray). The protein in the apo state (top; PDB entry 3i3r
) has a single chlorine ion in each TS active site (green spheres). Below are structures of BbDHFR-TS bound to dUMP, NADP and pemetrexed (middle; PDB entry 3k2h
) and complexed with dUMP, NADP and raltitrexed (bottom; PDB entry 3nrr
). Identical ligands are bound to protomer A (white, left) and protomer B (black, right) in each homodimer complex. Electron density (green mesh) is depicted for protomer A ligands at a 2.5σ contour level carved from a 1.6 Å atomic radius of the |Fo| − |Fc| maps using phases calculated from models lacking the ligand. This figure was created using CCP4 (Winn et al., 2011) and PyMOL (DeLano, 2002). |