How is the orientation of membrane proteins in the membrane thought to be accomplished?
A)After synthesis, an enzyme orients the protein properly.
B)During synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the cytosol.
C)During synthesis, the translocon inner lining orients the nascent polypeptide so the more negative end faces the cytosol.
D)During synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the mitochondrial intermembrane space.
E)After synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the cytosol.

Question

Quizplus · Accepted Answer

During synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the cytosol. This is known as the positive-inside rule and is accomplished through interactions with positively charged residues in the translocon lining. Additionally, membrane proteins may contain signal sequences that direct their insertion into the membrane in a specific orientation. Once inserted, interactions with lipids in the membrane may further stabilize the protein's orientation.

How Is the Orientation of Membrane Proteins in the Membrane