Question

During the transport cycle of the calcium ATPase, which of the following events causes the conformation change that enables transport of 2 calcium ions out of the cytosol?

A) Binding of ATP to the transporter
B) Release of phosphate from the transporter
C) Binding of calcium ions to the transporter
D) Hydrolysis of ATP by the transporter

Answer 1

The release of phosphate from the transporter is the event that causes the conformational change enabling the transport of 2 calcium ions out of the cytosol in the calcium ATPase transport cycle.

Step-by-step explanation:

The correct answer to the question is B) Release of phosphate from the transporter. In the calcium ATPase transport cycle, typically associated with the active transport of calcium ions out of the cytosol, a crucial step is the phosphorylation of the ATPase enzyme that leads to a conformational change, facilitating the transport of calcium ions.

Here are the steps that explain this process in brief:

1. Calcium ions bind to the ATPase, prompting the enzyme to have a high affinity for ATP.
2. The ATPase hydrolyzes ATP, which results in a phosphate group binding to the transporter and causing an initial shift in its shape (phosphorylation).
3. The transporter, now phosphorylated, goes through additional conformational changes, leading to the reorientation of the transporter, allowing calcium ions to be released outside the cytosol.
4. The release of the phosphate group is the step that triggers the transporter to revert back to its original conformation, with decreased affinity for calcium ions, thus concluding the transport cycle.