Third step in Ca2+ transport?

The shift to the E2 state causes ion binding sites to 'evert' so that the ions can dissociate into the luminal side of the membrane. ADP id exchanged for a fresh ATP resulting in the pump to open to the lumen of the SR releasing the calcium ions. binding of 2 H+ from the SR and the closing of the pump and the dephosphorylation of the P-domain