TABLE 1.

Parameters obtained for Ca²⁺ dependence of accumulation of ADP-insensitive EP in Y122-HC mutants As shown in Fig. 5, the lumenal Ca²⁺-induced change in the steady-state accumulation of ADP-insensitive EP of the seven Y122-HC mutants in the presence of 0.1 m K⁺ were fitted to the Hill equation. The parameters thus obtained by the least squares fit are listed here. K_0.5 is the Ca²⁺ concentration giving the half-maximum change in the fraction of ADP-insensitive EP among the total amount of EP, therefore the apparent affinity for lumenal Ca²⁺. The highest fraction of the ADP-insensitive EP at the low Ca²⁺ concentration range (0–10 μm) and its lowest fraction at the high Ca²⁺ concentration range (over ∼mm) are also listed as the obtained parameters in the fitting (see Fig. 5). The value n_H is the Hill coefficient.

Mutant	Fraction of ADP-insensitive EP at highest and lowest Ca2+ concentration ranges		K0.5	nH
	High Ca2+	Low Ca2+
	% of total amount of EP			mm
L119A	11	78	0.12	2.1
Y122A	6	86	0.16	1.9
I179A	12	92	0.25	2.3
L180A	9	44	0.11	1.6
I232A	10	89	0.32	2.0
V705A	39	80	0.27	1.6
V726A	23	65	0.28	2.0