This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
[{'content': 'Which of the following sequence is directed in a retrograde manner to EPR in COP-1 vesicles? \nSelect and explain. \nA. KDEL, B. KDAL, C. DALK, D. KDUL', 'role': 'user'}, {'content': 'Answer: A \nExplanation: KDEL sequence ( lysine - aspaate - glutamate - leucine ) at carboxy terminal first travel to GA in COP-2 vesicles, interact with their specific receptor protein. then they return in a COP-1 vesicle to EPR, get dissociate from their receptor & are retrieved. Reference: Harper; 30th edition', 'role': 'assistant'}]