If Sar1 is Inserted into the Membrane

Question

If Sar1 is inserted into the membrane:
A)it is bound to GTP and recruits COPII coat proteins.
B)it is bound to GDP and recruits COPII coat proteins.
C)it is bound to GTP and recruits cargo.
D)it is not bound to GTP or GDP.

Accepted Answer

Sar1 specifically binds to GTP when it is inserted into the membrane, which triggers the recruitment of COPII coat proteins. The COPII coat proteins then form a vesicle around the cargo proteins, allowing them to be transported to the Golgi apparatus. Therefore, option A is the correct choice as Sar1 binds to GTP and recruits COPII coat proteins. Option B and C are incorrect because they have incorrect binding states or functions for Sar1, while option D is incorrect because Sar1 does indeed bind to GTP when it is inserted into the membrane.