Figure 7.

Three-dimensional models of actin-tropomyosin-troponin⁸⁴⁾ as revealed by electron cryo-microscopy without assuming helical symmetry, and the atomic structure of the troponin arm.¹⁰²⁾ A. The structures of actin-tropomyosin-troponin. The outer domain and the myosin-binding sites of actin are indicated by arrows. B. The structures after subtracting the density due to actin, of which the atomic structure⁵⁰⁾ in wire format. C. The atomic model of the troponin arm.¹⁰²⁾ D. Enlarged view of the panel B. E. The models of actin-tropomyosin-troponin. A cross indicates the center of troponin arm, and an asterisk indicates the corresponding position, where three protomers meet. The myosin-binding sites⁸⁹⁾ on actin are shown in various colors (red, orange, yellow, green, cyan, and blue).