title: The lack of a solvent accessible hydroxide or water ligand to iron at the 3Fe center of Azotobacter vinelandii ferredoxin I.
abstract: The X-ray crystal structure of Azotobacter vinelandii ferredoxin I (FdI) describes a planar 3Fe-3S center in which one of the iron atoms is ligated to a solvent accessible oxo ligand, presumably from water or hydroxide (Ghosh et al., (1982) J. Mol. Biol. 158, 73-109). Efforts to displace the proposed oxo ligand with cyanide were unsuccessful, even in 80% dimethylsulfoxide. In addition, comparison of the electron spin echo envelopes for H2O- and D2O-equilibrated samples of FdI showed only a slight deuterium modulation, far less than would be expected were water to be bound as an iron ligand. These results do not support the presence of a solvent accessible oxo ligand to the 3Fe center as described in the X-ray crystal structure.
mesh_terms: D001395:Azotobacter / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000302:isolation & purification; D006878:Hydroxides; D009682:Magnetic Resonance Spectroscopy; D011489:Protein Denaturation; D012995:Solubility; D012997:Solvents; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D005288:Ferredoxins; D006878:Hydroxides; D012997:Solvents; D014867:Water