Sandbox Reserved 970: Difference between revisions

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[[Image:51-TheCalciumPumps-calcium-pumps.jpg|400px|center|]]<ref name="second"> David Goodsell, 2004 - Calcium pump molecul of the month - PDB, doi: 10.2210/rcsb_pdb/mom_2004_3</ref>
[[Image:51-TheCalciumPumps-calcium-pumps.jpg|400px|center|]]<ref name="second"> David Goodsell, 2004 - Calcium pump molecul of the month - PDB, doi: 10.2210/rcsb_pdb/mom_2004_3</ref>
The structure on the left is is the empty state. Two calcium ions are show in blue in the right structure.


To sum up, calcium pumps have two conformations, E1 and E2. These two conformations are characterized by different specificity for ion binding. When the pump is in the E1 state, it has high calcium affinity and interacts with calcium at one side of the membrane. In the E2 state, the enzyme has a lower calcium affinity and that leads to the release of the ion at the opposite side. E1 has the calcium binding site oriented toward the cytoplasm. E2 has the calcium binding site oriented toward the lumen of the endoplasmic reticulum or toward the extracellular background<ref>Thomas D.Pollard and William C. Earnshaw, - ''Membrane, structure and function'' - Cell Biology (second edition), p.133-136</ref>. The phosphorylated intermediate, E1 can phosphorylate ADP, whereas E2 can only react with water<ref>David H.MacLennan, William J.Rice and N. Michael Green, 1997 - ''The Mechanism of Ca2+ Transport by Sarco(Endo)plasmic Reticulum Ca2+-ATPases'' -  The Journal of Biological Chemistry, p.272, 28815-28818, http://www.jbc.org/content/272/46/28815.full.html</ref>.
To sum up, calcium pumps have two conformations, E1 and E2. These two conformations are characterized by different specificity for ion binding. When the pump is in the E1 state, it has high calcium affinity and interacts with calcium at one side of the membrane. In the E2 state, the enzyme has a lower calcium affinity and that leads to the release of the ion at the opposite side. E1 has the calcium binding site oriented toward the cytoplasm. E2 has the calcium binding site oriented toward the lumen of the endoplasmic reticulum or toward the extracellular background<ref>Thomas D.Pollard and William C. Earnshaw, - ''Membrane, structure and function'' - Cell Biology (second edition), p.133-136</ref>. The phosphorylated intermediate, E1 can phosphorylate ADP, whereas E2 can only react with water<ref>David H.MacLennan, William J.Rice and N. Michael Green, 1997 - ''The Mechanism of Ca2+ Transport by Sarco(Endo)plasmic Reticulum Ca2+-ATPases'' -  The Journal of Biological Chemistry, p.272, 28815-28818, http://www.jbc.org/content/272/46/28815.full.html</ref>.
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