Indicate whether the C-terminus (C) or the N-terminus (N) of each of the following proteins is expected to be located in the cytosol upon membrane integration of the protein. Your answer would be a three-letter string composed of letters C and N only, e.g. CCC.
( ) A single-pass transmembrane protein that has one N-terminal signal sequence and one internal stop-transfer signal
( ) A single-pass transmembrane protein that has one internal signal sequence that is preceded by a patch of positively charged residues
( ) An ER tail-anchored protein

Question

Indicate whether the C-terminus (C) or the N-terminus (N) of each of the following proteins is expected to be located in the cytosol upon membrane integration of the protein. Your answer would be a three-letter string composed of letters C and N only, e.g. CCC.
( )	A single-pass transmembrane protein that has one N-terminal signal sequence and one internal stop-transfer signal
( )	A single-pass transmembrane protein that has one internal signal sequence that is preceded by a patch of positively charged residues
( )	An ER tail-anchored protein

Quizplus · Accepted Answer

In the first case, the N-terminal signal sequence would be cleaved, placing the N-terminus in the endoplasmic reticulum lumen and the C-terminus in the cytosol. The "positive inside" rule applies to the second case, placing its N-terminus in the cytosol. Tail-anchored proteins always have their N-terminal bulk in the cytosol.

Indicate Whether the C-Terminus (C) or the N-Terminus (N) of Each