Table 4.

Inhibition of the magnesium chelatase activity by separately treating BchD, BchH, and BchI with Co(III)–ATP–o-phenanthroline

Subunits added to assay	Activity, % control
BchD + BchH + BchI	100
BchD + BchH + BchIt	80.5
BchDt + BchH + BchI	tr
BchD + BchHt + BchI	45.8
BchD + BchIt + BchHt	34.7
BchDt + BchH + BchIt	tr
BchDt + BchHt + BchI	tr
BchDt + BchHt + BchIt	tr

The chelatase subunits were treated with the inhibitor as described in Table 3. Magnesium chelatase activity was analyzed in stopped assays. Protein (μg per assay): BchD, 33; BchDt, 33; BchH, 210; BchHt, 210; BchI, 90; BchIt, 90. The control assay contained untreated BchD, BchH, and BchI, and the test assays contained different combinations of the treated subunits. tr, Trace.