clar697
Forum Guru
Topics: 190
Posts: 199
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Which of the following best explains why proteins synthesized in the rough endoplasmic reticulum and secreted from eukaryotic cells have a shorter length than would be predicted by their respective mRNAs?
A) Cleavage of 5’ segments of nascent polypeptides being synthesized on polyribosomes in the endoplasmic reticulum
B) Covalent binding if nascent polypeptides to a specific membrane proteins during their synthesis
C) Nonspecific protease activity during passage of these proteins through the endoplasmic reticulum membrane
D) Shortening of the carboxyterminus because hydrophobic amino acids remain within the membrane
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| zwmack
Forum Junior
Topics: 6
Posts: 39
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A) I think this is the answer because usually the 5' sequence is a signaling sequence added for destination purposes. I know that this is the case with Mannose 6 Phosphate being added to proteins destine for lysosomes so I cant think of a reason that similar signaling sequences wouldn't be present for those proteins traveling to the ER.
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