Figure 5.

S1 binding to an excess of the pyr-actin·sk αTm·cTn complex in the presence and absence of calcium. Observed transients for excess actin (2.5 μM ppA, 1 μM hcTn, and 1 μM sk αTm) binding to 0.25 μM S1 with or without Ca²⁺. Thin filaments were reconstituted with each Tm dimer. Five transients are shown (one for each Tm) in the presence or absence of calcium. E180G-Tm (gray line) in the presence of Ca²⁺ showed a slight variation. The best fit single-exponential k_obs values are listed in Table 3. Experimental conditions: as for Figure 4 with addition of 2 mM EGTA or 2 mM Ca-EGTA.