Figure 6. The effect the mutations on the actin affinity measured by cosedimentation with F-actin.

Binding to filamentous actin. Tropomyosin (0.1–10 µM, depending on the tropomyosin) and 0.12–12 µM troponin T_70–170 [44] were combined with 5 µM actin and sedimented at 20°C in 250 mM NaCl, 10 mM TrisHCl, pH 7.5, 2 mM MgCl₂, and 0.5 mM DTT. Stoichiometric binding of 1 tropomyosin: 7 actins is represented by the 1.0 fraction of maximal binding. The apparent K_apps are reported in Table 2. A. Symbols: •, wildtype; ○, P3Shift, ▾, P2Shift. B. Symbols: •, wildtype; ○, P2P3Shift. C. Symbols: •, wildtype; ○, P5→P3. The mutations affect the affinity and cooperativity of binding.