Nitrogenase from Bacillus polymyxa. Purification and properties of the component proteins

A purification procedure is described for the components of Bacillus polymyxa nitrogenase. The procedure requires the removal of interfering mucopolysaccharides before the two nitrogenase proteins can be purified by the methods used with other nitrogenase components. The highest specific activities obtained were 2750 nmol C2H4 formed . min-1 . mg-1 MoFe protein and 2521 nmol C2H4 formed . min-1 . mg-1 Fe protein. The MoFe protein has a molecular weight of 215 000 and contains 2 molybdenum atoms, 33 iron atoms and 21 atoms of acid-labile sulfur per protein molecule. The Fe protein contains 3.2 iron atoms and 3.6 acid-labile sulfur atoms per molecule of 55 500 molecular weight. Each Fe protein binds two ATP molecules. The EPR spectra are similar to those of other nitrogenase proteins. MgATP changes the EPR of the Fe protein from a rhombic to an axial-type signal.