Table 1.

Parameters measured for β-cardiac myosin sS1

	k0, s−1	δ, nm	d, nm	kcat, s−1	Kapp, μM	V, nm⋅s−1	pCa50	n
WT	104 ± 10	1.39 ± 0.06	5.2 ± 0.3	4.1 ± 0.4	33 ± 6	762 ± 16	6.46 ± 0.04	2.2 ± 0.2
P710R	87 ± 5	0.31 ± 0.03****	1.9 ± 0.3****	2.5 ± 0.1*	14 ± 1*	239 ± 9****	6.48 ± 0.07	3.1 ± 0.6

The rate of detachment from actin at zero load k₀, its force sensitivity δ, and myosin’s step size d were measured from single molecules using the HFS technique (8 WT and 13 P710R molecules). k_cat and K_app were measured using a colorimetric actin-activated ATPase assay and were previously reported (29). Unloaded motility velocities V were measured by the motility assay with actin filaments (nine WT and eight P710R independent experiments). Calcium sensitivity parameters pCa₅₀ and Hill coefficient n were measured by motility assay with regulated thin filaments (five WT and four P710R independent experiments). Data are presented as mean ± SEM. *P < 0.05 and ****P < 0.0001 different between P710R and WT.