How The Calcium Pump Works
Classical Theory of active transport for P-type ATPases
| E1 → | (2H+ out, 2Ca2+ in)→ | E1⋅2Ca2+ → | E1⋅ ATP |
| ↑ | ↓ | ||
| E2 | E1⋅ADP | ||
| ↑(Pi out) | ↓(ADP out) | ||
| E2⋅Pi | ← E2P | ←(2H+ in, 2Ca2+ out) | ← E1P |
Data from crystallography studies by Chikashi Toyoshima applied to the above cycle
| E1 - high affinity for Ca2+, 2 Ca2+ bound, 2 H+ counter ions released |
| E1⋅2Ca2+ - cytoplasmic gate open, free Ca2+ ion exchange occurs between bound ions and those in cytoplasm, closed configuration of N, P, A domains broken, exposing catalytic site |
| E1⋅ ATP - ATP binds and links N to P, P bends, N contacts A, A causes M1 helix to pull up, closes cytoplasmic gate, bound Ca2+ occluded in transmembrane |
| E1⋅ADP - Phosphoryl transfer, ADP dissociates |
| E1P - A rotates, transmembrane helices rearrange, binding sites destroyed, lumenal gate opened, bound Ca2+ released |
| E2P - open ion pathway to lumen, Ca2+ to lumen |
| E2⋅Pi - A catalyzes release of the Pi, P unbends, transmembrane helices rearranged, closes lumenal gate |
| E2 - transmembrane M1 forms cytoplasmic access tunnel to Ca2+ binding sites |
Read more about this topic: Calcium Pump
Famous quotes containing the words pump and/or works:
“My nurses, those starchy ghosts,
hover over me for my lame hours
and my lame days. The mechanics
of the body pump for their tricks.”
—Anne Sexton (1928–1974)
“They that go down to the sea in ships, that do business in great waters, these see the works of the Lord and his wonders in the deep.”
—Bible: Hebrew Psalms 107:23-24.