This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': "Which of the following is called a 'relaxation protein'? \nSelect and explain. \nA. Actin, B. Myosin, C. Tropomyosin, D. Dystrophin", 'role': 'user'}, {'content': 'Answer: C \nExplanation: 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', 'role': 'assistant'}]