Which of the following is called a 'relaxation protein'?
Troponin tropomyosin complex are called relaxation proteins and is found to inhibit the interaction between actin and myosin thereby preventing cross bridge formation. During resting stage troponin I is lightly bound to actin and the tropomyosin molecules are located in the groove between the strands of actin filaments in such a way that they block the myosin binding sites on actin. When activation occurs, calcium released into the sarcoplasmic reticulum gets attached to the troponin C subunit of troponin. This in turn cause a conformational change which cause the tropomyosin molecule to move laterally uncovering the binding sites on the actin filament for the head of myosin molecules. Ref: Essentials Of Medical Physiology By Khurana, page 51
Actin
Myosin
Tropomyosin
Dystrophin