Table 2.

Apparent K_d values for steady-state binding to G-actin when filament ends are capped

	Plant actin	Muscle actin
AtCAP1	0.5 ± 0.2 (6)	0.6 ± 0.2 (7)
ZmPRO5	0.19 ± 0.08 (4)	0.71 ± 0.14 (4)
HPRO1	n.d.	0.37 ± 0.13 (5)

n.d., not determined.

The apparent K_dvalues (micromolar, mean ± SD [n]) for AtCAP1 binding to rabbit muscle actin and maize pollen actin (plant) with 1:200 gelsolin–actin were determined by the shift in C_c at steady state at 100 nM free Ca²⁺. The C_c for plant and muscle actin was 1.2 ± 0.2 (13) and 0.56 ± 0.07 (6), respectively, when filament ends were capped. The apparent K_d for human profilin (HPRO1) binding to plant actin could not be measured using this method.