Question

The Aeroschmidt weed contains an ATP-driven ion pump in its vacuolar membrane that pumps potentially toxic heavy metal ions such as Zn2+ and Pb2+ into the vacuole. The pump protein exists in a phosphorylated and an unphosphorylated form and works in a similar way to the Na+-K+ pump of animal cells. To study its action, you incorporate the unphosphorylated form of the protein into phospholipid vesicles containing K+ in their interiors. (You ensure that all of the protein molecules are in the same orientation in the lipid bilayer.) When you add Zn2+ and ATP to the solution outside such vesicles, you find that Zn2+ is pumped into the vesicle lumen. You then expose vesicles containing the pump protein to the solutes as shown in Table 12-17A.What would you expect to happen if you treat vesicles as in lane F, but before determining the phosphorylation state of the protein you wash away the outside buffer and replace it with a buffer containing only Zn2+?

(a) Nothing will happen. (No Zn2+ will move into the vesicle; no K+ will move out of the vesicle; the phosphorylation state of the protein will not change.)
(b) No Zn2+ will move into the vesicle; no K+ will move out of the vesicle; the protein will become unphosphorylated.
(c) A small amount of Zn2+ will move into the vesicle; no K+ will move out of the vesicle; the phosphorylation state of the protein will not change.
(d) A small amount of Zn2+ will move into the vesicle; no K+ will move out of the vesicle; the protein will become unphosphorylated.

Answer 1

When vesicles containing the unphosphorylated form of the pump protein are treated as in lane F, but the outside buffer is washed away and replaced with a buffer containing only Zn2+, a small amount of Zn2+ will move into the vesicle.

Step-by-step explanation:

When vesicles containing the unphosphorylated form of the pump protein are treated as in lane F, but the outside buffer is washed away and replaced with a buffer containing only Zn2+, a small amount of Zn2+ will move into the vesicle. No K+ will move out of the vesicle, and the phosphorylation state of the protein will not change.