Fig. 3.
Effects of NifI1,2 and 2OG on nitrogenase activity. (A) Acetylene (C2H2) reduced per milligram of nitrogenase (75 μg each of NifH and NifDK) as a function of time, with or without 10 mM 2OG or 60 μg of NifI1,2. Data are from a representative experiment. (Inset) A Coomassie-stained SDS/PAGE gel of the purified NifH, NifDK, and NifI1,2. (B) The effect on nitrogenase activity of increasing amount of NifI1,2 as a fraction of the nitrogenase activity in the absence of NifI1,2. The concentration of NifI1,2 is expressed as a ratio to the total amount of dinitrogenase (NifDK, 75 μg) in the reaction. Results from three independent experiments (circles, diamonds, and triangles) and the average (solid line) are shown. (C) Nitrogenase activity without (filled squares) or with (open diamonds) 60–75 μg of NifI1,2 as a function of 2OG concentration, expressed as the fraction of activity without NifI1,2 or 2OG. Error bars show the SEM of at least three independent experiments.