Table 1. Half-times (t_1/2) for dissociation at 22 °C of trapped complexes of Pgp formed from ATP or ADP in the presence of Mg²⁺ or Co²⁺ ions.

Dissociation of trapped complexes of Pgp was indicated by recovery of catalytic activity. Trapped complexes were formed with ATP/ADP, and either Mg²⁺ or Co²⁺, in the presence of V_i, BeF_x or AlF_x. After isolation by gel-filtration chromatography, the complexes were incubated at 22 °C for various times, and their ATPase activity was determined, using a 10 min assay time, relative to a sample of native Pgp subjected to a mock treatment without trapping agent. Two independent experiments were carried out for determination of each value of t_1/2, with different preparations of Pgp and the three trapped complexes in each case. For the breakdown of trapped complexes formed in the presence of Co²⁺, t_1/2 values were estimated directly from kinetic plots of ATPase activity versus time. For breakdown of trapped complexes formed in the presence of Mg²⁺, the kinetic plots were fitted to a first-order rate equation, and values of t_1/2 were obtained by the fitting process.

		t1/2 for dissociation of trapped complexes
	Trapping agent	Mg2+ (min)	Co2+ (h)
ATP	Vi	61	11
	BeFx	35	8.5
	AlFx	32	5.7
ADP	Vi	68	11
	BeFx	35	8.6
	AlFx	32	6.0