Molybdenum nitrogenase of Azotobacter chroococcum. Tight binding of MgADP to the MoFe protein.
The dye-oxidized or dithionite-reduced forms of the MoFe protein of molybdenum nitrogenase of Azotobacter chroococcum were shown to bind 2 mol of MgADP/mol of protein, as determined by column equilibrium techniques. The gel-filtration elution profile of unbound Mg[14C]ADP was not symmetrical, consistent with a low rate of dissociation from the protein. Symmetrical elution profiles were observed for the oxidized Fe protein of nitrogenase, which bound 2 mol of MgADP/mol of protein. The low rate of dissociation of MgADP from MoFe protein was shown by non-equilibrium column techniques, where 1 mol of MgADP/mol of MoFe protein remained tightly bound during chromatography. Very weak binding of MgATP (less than 0.01 mol of MgATP/mol of MoFe protein) to dye-oxidized but not to dithionite-reduced MoFe protein was observed. These results are discussed in terms of their relevance to the catalytic cycle of nitrogenase catalysis.
Miller
R W
RW
Plant Research Centre, Agriculture Canada, Ottawa, Ontario.
Eady
R R
RR
D000244:Adenosine Diphosphate / Q000378:metabolism*; D001395:Azotobacter / Q000201:enzymology*; D002850:Chromatography, Gel; D007501:Iron; D046911:Macromolecular Substances; D008982:Molybdenum; D009591:Nitrogenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding
D046911:Macromolecular Substances; D000244:Adenosine Diphosphate; D008982:Molybdenum; D007501:Iron; D009591:Nitrogenase