2. A scientist isolates two specific mRNAs. One codes for the enzyme fowlase, an
ID: 272777 • Letter: 2
Question
2. A scientist isolates two specific mRNAs. One codes for the enzyme fowlase, an enzyme that is involved in digestion in chickadees; the other codes for the quail enzyme quailase that is involved in cellular carbohydrate metabolism. Both mRNAs are placed in a test tube with RER vesicles stripped of their ribosomes, free ribosomes and precursors for protein synthesis. When the protein synthesis reaction is complete, fowlase is found inside the vesicles; quailase is found in the liquid portion of the test tube outside the vesicles. What can one conclude about the two proteins?Explanation / Answer
2. We can conclude that the enzyme quailase which is found in the liquid portion will be a cytosolic protein. The translation of this protein occurs on membrane free ribosomes in the liquid portion. It may enter the RER vesicles for post translational modifications and then exit back into the liquid portion equivalent to cytosol.
The enzyme fowlase which is found in the RER will be a protein of the secretory pathway involving RER, Golgi and lysosomes. Since this enzyme is involved in digestion, it may be a lysosomal protein. It will be cotranslationally translocated into RER vesicles. Since there is no Golgi and lysosomes, the protein will remain in the RER vesicles.
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