This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Smooth Muscle, Subject name: Physiology
[{'content': 'Which of the following is not a calcium binding protein? \nSelect and explain. \nA. Calbindin, B. Calmodulin, C. Troponin, D. Clathrin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Clathrin (does not bind ca2+) On inside of cell membrane beneath coated pits, latticework of fibrillar protein is present called clathrin Helps in pinocytosis Calbindin Present in brush border of intestinal epithelial cells & transpo Ca+2 into cell cytoplasm Amount of calcium absorption is directly propoional to quantity of calcium-binding proteins Troponin: Troponin C - binds to Ca+2 ions = Strong affinity of troponin to calcium initiate contraction process. Calmodulin In place of troponin, smooth muscle have calmodulin Ca+2 inside cell bind reversibly with calmodulin & activates myosin light chain kinase resulting in chain of events which cause muscle contraction', 'role': 'assistant'}]