Question: You perform a series of experiments on the synthesis of the pituitary hormone prolactin, which is…
Show transcribed image text You perform a series of experiments on the synthesis of the pituitary hormone prolactin, which is a single polypeptide chain 199 amino acids long. In the first experiment, the mRNA coding for prolactin is translated in a cell-free protein synthesizing system containing ribosomes, amino acids, tRNAs, aminoacyl-tRNA synthetases, ATP, GTP, and the appropriate initiation, elongation, and termination factors. Under these conditions, a polypeptide chain 227 amino acids long is synthesized. In a second experiment, the mRNA is translated in the same cell-free system to which you have added SRP. In this case, translation stops after a peptide about 70 amino acids long has been produced. In a third experiment, you use the same cell-free translation system to which you have added both SRP and endoplasmic reticulum vesicles, and you find that that the prolactin mRNA now produces a polypeptide that is 199 amino acids long. Explain these results. Where would you expect to find the polypeptide produced in experiment 3?
You perform a series of experiments on the synthesis of the pituitary hormone prolactin, which is a single polypeptide chain 199 amino acids long. In the first experiment, the mRNA coding for prolactin is translated in a cell-free protein synthesizing system containing ribosomes, amino acids, tRNAs, aminoacyl-tRNA synthetases, ATP, GTP, and the appropriate initiation, elongation, and termination factors. Under these conditions, a polypeptide chain 227 amino acids long is synthesized. In a second experiment, the mRNA is translated in the same cell-free system to which you have added SRP. In this case, translation stops after a peptide about 70 amino acids long has been produced. In a third experiment, you use the same cell-free translation system to which you have added both SRP and endoplasmic reticulum vesicles, and you find that that the prolactin mRNA now produces a polypeptide that is 199 amino acids long. Explain these results. Where would you expect to find the polypeptide produced in experiment 3?
