Table 2.

Synthesis of dinitrogenase in extracts of strain DJ54 incubated with NifH or apoNifH

Pretreatment*	Activity†
NifH	21.9
ApoNifH	21.6
None‡	0.13

^*The reaction mixture contained 6 ml of extract (≈12 mg of protein/ml) of strain DJ54 preincubated with an excess of purified FeMo-co N-methyl-formamide (equivalent to 13 nmol of Mo), 1.5 ml of an ATP-regenerating mixture, and purified NifH or apoNifH, as described.

^†A 25-μl aliquot of the fraction (0.21 mg of protein) was tested for dinitrogenase activity by the addition of excess purified NifH (0.1 mg of protein), ATP-regenerating mixture, and 0.5 ml C₂H₂. Activity is expressed as nmol of C₂H₄ formed per min/mg protein.

^‡The reaction mixture was similar to the one described above except that it contained no source of NifH in the preincubation phase.