Table 1. Dissociation constants for the α & β Tm constructs with and without the AS-extension.

K_50% values and the Hill cooefficient (h) were calculated via the Hill Equation from the Tm/actin binding plot featured in fig. 1 and were measured from the best fit to the Hill equation as the free Tm concentration at which the actin filament is half saturated by Tm. The errors on the fits to the data were all less than 10% of the value for K_50% but much larger for h; 15-30% for values of 1-1.5 and 30-50% for values above 1.5. Thus differences in the values of h are not significant. K_T and n values were obtained from the fit of the sigmoid titration curves to the 2-state model of McKillop and Geeves.

Tm	K50% (μM)	h	KT	n
ASα-Tm	0.035	2.65	0.1-0.25	5-9
α-Tm	2.22	1.42	0.12	5-9
ASβ-Tm	0.30	1.33	0.05-0.15	5-9
β-Tm	>20	-	ND	ND
ASα/ASβ-Tm	0.03	3.05	0.1-0.25	5-9
Native Gizzard Tm	0.04	1.37	0.1-0.3	5-9
Sk ASα-Tm	0.18*	2.05	0.1+	7+
Sk ASβ-Tm	0.23*	1.6	ND	ND

^*Data from Boussouf et al submitted. The affinities without an AS extension were > 20 μM

⁺Data from Maytum et al 2001 [KCl] 200 mM

ND not determined