Table 3.

Inhibition of ATPase activities of the magnesium chelatase subunits with Co(III)–ATP–o-phenanthroline

Assay	Subunits added	ATPase activity, % control
1	BchD + BchI	100
2	BchDt + BchI	45.9
3	BchD + BchIt	99.2
4	BchDt + BchIt	45.1
5	BchH	100
6	BchHt	41.1

The subunits in a buffer containing 20 mM Tricine-NaOH at pH 9.0 and 1 mM DTT were incubated for 5 min on ice with the inhibitor (10 mM), and excess inhibitor was removed by passing through a NAP-5 column. These treated proteins (BchDt, BchIt, and BchHt) were analyzed against the untreated proteins for ATPase activity. Protein (μg per assay): BchD, 33; BchDt, 33; BchH, 210; BchHt, 210; BchI, 90; BchIt, 90.