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 of nascent polypeptides to specific membrane proteins during their synthesis
C. Nonspecific protease activity during passage of these proteins through the endoplasmic reticulum membrane
D. Shortening of the carboxy terminus because hydrophobic amino acids remain within the membrane
A. Cleavage of 5¢ segments of nascent polypeptides being synthesized on polyribosomes in the endoplasmic reticulum
B. Covalent binding of nascent polypeptides to specific membrane proteins during their synthesis
C. Nonspecific protease activity during passage of these proteins through the endoplasmic reticulum membrane
D. Shortening of the carboxy terminus because hydrophobic amino acids remain within the membrane