Fig. 9.

Consequences of the loss of troponin function. (A) Schematic depiction of sarcomeres in the wild-type condition in which troponin (blue ovals), on thin filaments (thick blue lines) together with tropomyosin, regulates actin–myosin interactions. Thick filaments are shown in green. (B) In the absence of troponin, sarcomeres do not form, instead stacks of thick filaments, expanded Z lines (black ovals) and aggregates of filamentous actin (blue clouds) can be observed. (C) If in the absence of troponin, the actin–myosin activity is blocked, then sarcomeres form although filamentous actin (thin blue lines) does not associate with tropomyosin and Z lines are expanded.