Table 1. Experimental and calculated rate constants for the association of seven actin-binding proteins with G-actin.

		Experiment			Calculation
ABP	PDB	k a (M−1 s−1)	I b (mM)	Ref.	k a (M−1 s−1)	k a0 (M−1 s−1)	ΔG el* (kcal/mol)
Profilin	2BTF	1.4×107	110	[5]	1.04×107	3.60×105	−1.99
Twinfilin ADF-H 2	3DAW	2.36×107	110	[7]	1.22×107	7.90×105	−1.62
Gelsolin domain 1	1EQY	3.0×105	16	[3]	2.00×105	1.14×106	1.03
WASP WCA	2A3Z	4.3×107	65	[6]	1.65×107	2.53×106	−1.11
Ciboulot domain 1	1SQK	1.2×106	10	[8]	0.87×106	3.03×105	−0.62
Tβ4	1SQK/1T44a	1.7×106	5	[9]	4.04×106	7.52×105	−0.99
DBP	1KXP	2.2×104	12	[4]	1.59×104	7.42×104	0.91

^aThe complex of Tβ4 with G-actin was modeled by merging PDB entries 1SQK and 1T44 (see Methods for details).

^bIonic strength.