Table 2.

Rate and equilibrium constants for key steps of the actomyo1b^a ATPase cycle in the absence and presence of 100 μM calcium at 20°C^∗

ATP binding
	− Calcium	+ Calcium
1/K1′ (μM)†	420 ± 29	480 ± 32
k+2′ (s−1)†	31 ± 0.70	70 ± 1.6
K1′k+2′ (μM−1s−1)‡	0.074 ± 0.0054	0.15 ± 0.011
ADP release
	− Calcium	+ Calcium
K5′ (μM)†	0.57 ± 0.034	1.48 ± 0.027
k+5′ (s−1)†	2.1 ± 0.13	5.0 ± 0.44
k-5′ (μM−1s−1)‡	3.6 ± 0.031	3.4 ± 0.30
Nucleotide-free isomerization step
	− Calcium	+ Calcium
Kα†	1.5± 0.090	2.8 ± 0.26
k+α (s−1)†	2.4 ± 0.39	7.9 ± 0.30
k-α (s−1)‡	1.6 ± 0.28	2.8 ± 0.28

^∗KMg25 (10 mM MOPS (pH 7.0), 25 mM KCl, 1mM EGTA, 1mM DTT, 1mM MgCl₂, ±100μM Ca²⁺_F, 20°C).

^†Pyrene-actin fluorescence.

^‡Calculated.