Can the local enzyme scaffold act as an H-donor for a Co(I)H bond formation? The curious case of methionine synthase-bound cob(I)alamin

The density functional calculations suggest that the Y1139 residue of methionine synthase (MetH) enzyme forms a stronger Co(I)H interaction than the β-axial H2O ligand. The analysis of the X-ray crystallographic data also indicates that the Y1139 residue in the MetH-bound cobalamin may be the actual β-axial ligand rather than the H2O.