And the A domain actually links that conformational change in these two domains to the conformational change in the transmembrane domain. So the A domain is responsible for stimulating the conformational change, as we'll see in just a moment. So let's actually take a look at the details of how the calcium Atph actually works. And notice we have six different diagrams and this basically cycles back and forth. So let's begin with the starting point, this diagram here. So this is known as the e one state of this protein.