Table 2.

Summary of steady-state and transient kinetic results comparing WT and mutants

	WT	R723G	F764L
Steady-state ATPase values (± SEM), N = 3–6
v0 (s−1)	0.02 ± 0.01	0.03 ± 0.01	0.02 ± 0.01
kcat (s−1)	8.3 ± 1.1	6.1 ± 1.5	6.4 ± 1.4
KATPase (μM)	78 ± 16	60 ± 26	70 ± 25
In vitro motility value (± SEM), N = 90
Mean velocity (nm/s)	1591 ± 16	1699 ± 17∗	1425 ± 16∗
Rate/equilibrium constants (± SEM)	WTa	R723G	F764La
ATP binding/hydrolysis (myosin), N = 2b
K0.5 (μM)	48 ± 6	48 ± 9	79 ± 6
K1Tk+2T (μM−1 s−1)	2.8 ± 0.1	3.9 ± 0.1	1.9 ± 0.1
k+H + k-H (s−1)	182 ± 6	231 ± 12	166 ± 6
ATP binding (actomyosin), N = 3c
K′1Tk′+2T (μM−1 s−1)	9.6 ± 0.2	8.2 ± 0.1	9.4 ± 0.2
K0.5 (μM)	31 ± 9	42 ± 22	24 ± 8
k′+2T (s−1)	512 ± 47	668 ± 121	409 ± 42
Actin-activated Pi release at 30 μMd
k′+Pi (fast, s−1)	20.7 ± 0.9	ND	16.4 ± 1.7
k′+Pi (slow, s−1)	1.86 ± 0.02	ND	1.68 ± 0.01
Actin-activated power stroke, N = 3–4e
k′+PW (fast phase, maximal rate, s−1)	17.2 ± 4.8	10.8 ± 4.1	8.7 ± 4.5
K0.5, fast (μM)	48 ± 33	29 ± 19	29 ± 26
k′+PW (slow phase, at 30 μM actin, s−1)	1.5 ± 0.3	0.9 ± 0.2	0.8 ± 0.3
Actomyosin ADP releasef
k′+D (s−1), N = 3–5f	332 ± 57	380 ± 55	290 ± 46
k′+D (s−1), N = 3c	174 ± 12	218 ± 15∗	132 ± 16∗

^∗p < 0.05. ND, not determined.

^aValues acquired from Tang et al. (25) except for the power-stroke parameters.

^bIntrinsic tryptophan fluorescence.

^cPyrene actin.

^dMDCC-PBP fluorescence.

^eFRET.

^fmant-ADP fluorescence.