Sandbox Reserved 970: Difference between revisions

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The first step of the calcium pump catalytic cycle is the cooperative binding of <scene name='60/604489/Calcium_molecules/1'>two calcium ions</scene> in the calcium binding cavity. Then, ATP binds to the ATP binding site (nucleotide binding domain) and transfers its γ-phosphate to the aspartic acide 351 (phosphorylation domain). That creates a acid-stable aspartyl phosphate intermediate. The phosphorylation of Asp351 allows a large conformational changes in cytoplasmic domains: the nucleotide binding domain and the phosphorylation domain are brought into close proximity. This rearrangement causes a 90° rotation of the activator domain, which leads to a rearrangement of the transmembrane helices. This rearrangement alters the affinity of the protein for the calcium and disrupts the calcium binding cavity. Calcium is released in the lumen of the endoplasmic reticulum/Golgi Apparatus or outside the cell. After releasing calcium, two protons are bound to the transport sites (charges compensation) and the aspartyl phosphate is hydrolyzed to complete the cycle.

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 ~~<scene name='60/604489/E1_state_3w5a/1'>~~E2 state~~</scene>~~, 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.

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 <scene name='60/604489/E1_state_3w5a/1'>E1 state</scene>, 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.

Sandbox Reserved 970: Difference between revisions

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Revision as of 17:42, 2 January 2015 view source Déborah Kreyenbihler (talk \| contribs) 62 edits No edit summary ← Older edit		Revision as of 17:46, 2 January 2015 view source Déborah Kreyenbihler (talk \| contribs) 62 edits No edit summary Newer edit →
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	The first step of the calcium pump catalytic cycle is the cooperative binding of <scene name='60/604489/Calcium_molecules/1'>two calcium ions</scene> in the calcium binding cavity. Then, ATP binds to the ATP binding site (nucleotide binding domain) and transfers its γ-phosphate to the aspartic acide 351 (phosphorylation domain). That creates a acid-stable aspartyl phosphate intermediate. The phosphorylation of Asp351 allows a large conformational changes in cytoplasmic domains: the nucleotide binding domain and the phosphorylation domain are brought into close proximity. This rearrangement causes a 90° rotation of the activator domain, which leads to a rearrangement of the transmembrane helices. This rearrangement alters the affinity of the protein for the calcium and disrupts the calcium binding cavity. Calcium is released in the lumen of the endoplasmic reticulum/Golgi Apparatus or outside the cell. After releasing calcium, two protons are bound to the transport sites (charges compensation) and the aspartyl phosphate is hydrolyzed to complete the cycle.		The first step of the calcium pump catalytic cycle is the cooperative binding of <scene name='60/604489/Calcium_molecules/1'>two calcium ions</scene> in the calcium binding cavity. Then, ATP binds to the ATP binding site (nucleotide binding domain) and transfers its γ-phosphate to the aspartic acide 351 (phosphorylation domain). That creates a acid-stable aspartyl phosphate intermediate. The phosphorylation of Asp351 allows a large conformational changes in cytoplasmic domains: the nucleotide binding domain and the phosphorylation domain are brought into close proximity. This rearrangement causes a 90° rotation of the activator domain, which leads to a rearrangement of the transmembrane helices. This rearrangement alters the affinity of the protein for the calcium and disrupts the calcium binding cavity. Calcium is released in the lumen of the endoplasmic reticulum/Golgi Apparatus or outside the cell. After releasing calcium, two protons are bound to the transport sites (charges compensation) and the aspartyl phosphate is hydrolyzed to complete the cycle.

	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 ~~<scene name='60/604489/E1_state_3w5a/1'>~~E2 state~~</scene>~~, 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.		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 <scene name='60/604489/E1_state_3w5a/1'>E1 state</scene>, 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.