7.6.2.8 BtuCD-F complex analyzed at a resolution of 2.6 A, substantial conformational changes observed as compared with previously reported structures of BtuCD and BtuF 690056 7.6.2.8 BtuCD-F complex, and HI470/1 X-ray diffraction structure analysis using PDB-IDs 2NQ2, 1L7V and 2QI9, overview 696776 7.6.2.8 crystal structure analysis of the crystal structure of the BtuCD-F complex, modelling, overview 697950 7.6.2.8 catalytically impaired BtuCD mutant E159Q in complex with BtuF, to 3.5 A resolution. The BtuC subunits adopts a distinct asymmetric conformation. The structure suggests that BtuF does not discriminate between, or impose, asymmetric conformations of BtuCD 719509 7.6.2.8 elucidation of gating mechanism by EPR spectroscopy. The translocation gates of the BtuCDF complex undergo conformational changes in line with a two-state alternating access model. Binding of ATP drives the gates to an inward-facing conformation. Following ATP hydrolysis, the translocation gates restore to an apo-like conformation. In the presence of ATP, an excess of vitamin B12 promotes the reopening of the gates toward the periplasm and the dislodgement of BtuF from the transporter 719987 7.6.2.8 molecular dynamics simulations to explore the atomic details of the conformational transitions of BtuCD importer. The outward-facing to inward-facing transition is initiated by the conformational movement of nucleotide-binding domains. The subsequent reorientation of the substrate translocation pathway at transmembrane domains begins with the closing of the periplasmic gate, followed by the opening of the cytoplasmic gate in the last stage of the conformational transition due to the extensive hydrophobic interactions at this region, consistent with the functional requirement of unidirectional transport of the substrates. The reverse inward-facing to outward-facing transition exhibits intrinsic diversity of the conformational transition pathways and significant structural asymmetry 720849 7.6.2.8 mutant E159Q/N162C in complex with adenylyl imidodiphosphate, sitting drop vapor diffusion method, using 100 mM ADA buffer, pH 6.9, 1.2 M NaCl, and 14-18% (w/v) PEG 2000 MME 734760 7.6.2.8 in complex with beta-gamma-imidoadenosine 5'-triphosphate, sitting drop vapor diffusion method, using 20-30% (w/v) PEG 400, 100 mM N-(2-acetamido)-iminodiacetic acid, pH 6.8, 100 mM sodium potassium citrate 734771 7.6.2.8 vitamin B12-bound VcBtuF, protein in a solution with vitamin B12 in a 3:1 ratio, and 50 mM Tris-HCl, pH 7.0, and 300 mM NaCl, mixing of 0.003 ml of protein solution with 0.002 ml of precipitant solution containing 0.8 M ammonium sulfate, 0.1 M Tris, pH 8.0, and equilibration against a reservoir solution containing 0.5 ml of 1.6 M ammonium sulfate, 0.1 M HEPES, pH 7.0, 20°C, 7 days, hanging drop vapour diffusion method, X-ray diffraction structure determination and analysis at 1.67 A resolution 749978 7.6.2.8 purified recombinant wild-type BtuCD-F, apo-BtuCD-F, and BtuCD-F mutant E159Q/N162C, X-ray diffraction structure determination and analysis 750063