Table II.

The Rates of Kinetic Steps of Actomyosin ATPase Cycle With Metal.Nucleotide as a Ligand

Cation	Ionic radius, Angstroms	Coordination number	Actin binding to myosin.ADP, µM−1 s−1	ATP induced actomyosin.ADP dissociation, µM	ATP induced actomyosin dissociation, µM−1 s−1
Mg2+	0.72	6	1.69 ± 0.13	16.7 ± 1.9	1.64 ± 0.16
Mn2+	0.83	6	1.29 ± 0.39	11.2 ± 1.6	1.71 ± 0.29
Ca2+	1.0	7	1.61 ± 0.26	34.1 ± 3.7	0.35 ± 0.01