troponin and tropomysin

troponin and tropomysin

the control proteins, components of the thin filaments in striated muscle, that work in partnership. Troponin has high affinity for calcium ions, which are released into the cytoplasm from the sarcoplasmic reticulum in response to excitation. When ionized calcium (Ca2+) binds to it, the troponin molecule changes shape and in so doing, is thought to move the associated tropomyosin molecule around the thin filament, making previously masked binding sites on a number of actin molecules accessible to the head-groups of myosin. The resultant myosin/actin interaction then develops force. See also myofibrils.