Figure 6.

Binding of S1 to excess pyrene-labeled actin filaments containing tropomyosin and troponin in the absence of ATP at saturating Ca²⁺. (A) Averages of ≥5 time courses of binding to actin filaments containing troponin with wild-type troponin T, curve 1; Δ8 troponin T, curve 2; and Δ14 troponin T, curve 3. Dashed lines are single exponential fits of the data. (B) The observed rate of binding of S1 to actin-tropomyosin containing troponin with different mutants of troponin T is shown. Error bars shown are the SDs. Conditions are as follows: the same as those in Fig. 5, except that 0.2 mM Ca²⁺ was substituted for the EGTA. The dashed line shows the expected behavior if each residue contributed equally to the effect measured.