calcium ion import into sarcoplasmic reticulum
Definition
Target type: biologicalprocess
The directed movement of calcium ions into a sarcoplasmic reticulum. [GOC:BHF, PMID:17286271]
Calcium ion import into the sarcoplasmic reticulum (SR) is a crucial step in muscle contraction and relaxation. It is a tightly regulated process that involves the coordinated action of several proteins, including the SR Ca2+ ATPase (SERCA) pump, ryanodine receptors (RyRs), and various regulatory proteins.
1. **Calcium release from the SR**: Muscle contraction is initiated by a nerve impulse that triggers the release of calcium ions from the SR through RyRs. These receptors are located on the SR membrane and form calcium release channels.
2. **SERCA pump activation**: After contraction, the calcium concentration in the cytosol needs to be lowered to allow muscle relaxation. This is achieved by the SERCA pump, which actively pumps calcium ions back into the SR against their concentration gradient.
3. **Calcium binding to SERCA**: The SERCA pump has two high-affinity calcium binding sites located in its cytosolic domain. When calcium ions bind to these sites, it triggers a conformational change in the pump, initiating the transport cycle.
4. **Calcium translocation**: The conformational change allows calcium ions to move from the cytosol across the SR membrane and into the SR lumen. This movement is coupled to the hydrolysis of ATP, providing the energy necessary for active transport.
5. **Phosphorylation and dephosphorylation**: During the transport cycle, the SERCA pump undergoes phosphorylation and dephosphorylation events. Phosphorylation activates the pump, allowing calcium to be transported, while dephosphorylation resets the pump to its original state.
6. **Regulation of SERCA activity**: Several regulatory proteins, including phospholamban (PLN) and sarcolipin (SLN), influence SERCA activity. PLN inhibits SERCA activity, while SLN enhances it.
7. **Calcium accumulation in the SR**: Through the continuous action of the SERCA pump, calcium ions are accumulated in the SR lumen, creating a concentration gradient that favors calcium release during the next muscle contraction cycle.
This intricate process ensures the rapid and efficient removal of calcium from the cytosol, allowing muscle relaxation and preparing the muscle for subsequent contractions.'
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Proteins (2)
| Protein | Definition | Taxonomy |
|---|---|---|
| Sarcoplasmic/endoplasmic reticulum calcium ATPase 2 | A sarcoplasmic/endoplasmic reticulum calcium ATPase 2 that is encoded in the genome of human. [PRO:DNx, UniProtKB:P16615] | Homo sapiens (human) |
| Sarcoplasmic/endoplasmic reticulum calcium ATPase 1 | A sarcoplasmic/endoplasmic reticulum calcium ATPase 1 that is encoded in the genome of human. [PRO:DNx, UniProtKB:O14983] | Homo sapiens (human) |
Compounds (7)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| 2,5-di-tert-butylhydroquinone | 2,5-di-tert-butylbenzene-1,4-diol : A member of the class of hydroquinones that is benzene-1,4-diol substituted by tert-butyl groups at position 2 and 5. | hydroquinones | |
| chelerythrine | chelerythrine : A benzophenanthridine alkaloid isolated from the root of Zanthoxylum simulans, Chelidonium majus L., and other Papaveraceae. | benzophenanthridine alkaloid; organic cation | antibacterial agent; antineoplastic agent; EC 2.7.11.13 (protein kinase C) inhibitor |
| paxilline | paxilline : An indole diterpene alkaloid with formula C27H33NO4 isolated from Penicillium paxilli. It is a potent inhibitor of large conductance Ca2(+)- and voltage-activated K(+) (BK)-type channels. paxilline: structure given in first source; RN given refers to (2R-(2alpha,4bbeta,6aalpha,12bbeta,12calpha,14abeta))-isomer | diterpene alkaloid; enone; organic heterohexacyclic compound; terpenoid indole alkaloid; tertiary alcohol | anticonvulsant; Aspergillus metabolite; EC 3.6.3.8 (Ca(2+)-transporting ATPase) inhibitor; genotoxin; geroprotector; mycotoxin; Penicillium metabolite; potassium channel blocker |
| thapsigargin | thapsigargin : An organic heterotricyclic compound that is a hexa-oxygenated 6,7-guaianolide isolated fron the roots of Thapsia garganica L., Apiaceae. A potent skin irritant, it is used in traditional medicine as a counter-irritant. Thapsigargin inhibits Ca(2+)-transporting ATPase mediated uptake of calcium ions into sarcoplasmic reticulum and is used in experimentation examining the impacts of increasing cytosolic calcium concentrations. Thapsigargin: A sesquiterpene lactone found in roots of THAPSIA. It inhibits SARCOPLASMIC RETICULUM CALCIUM-TRANSPORTING ATPASES. | butyrate ester; organic heterotricyclic compound; sesquiterpene lactone | calcium channel blocker; EC 3.6.3.8 (Ca(2+)-transporting ATPase) inhibitor |
| curcumin | curcumin : A beta-diketone that is methane in which two of the hydrogens are substituted by feruloyl groups. A natural dyestuff found in the root of Curcuma longa. Curcumin: A yellow-orange dye obtained from tumeric, the powdered root of CURCUMA longa. It is used in the preparation of curcuma paper and the detection of boron. Curcumin appears to possess a spectrum of pharmacological properties, due primarily to its inhibitory effects on metabolic enzymes. | aromatic ether; beta-diketone; diarylheptanoid; enone; polyphenol | anti-inflammatory agent; antifungal agent; antineoplastic agent; biological pigment; contraceptive drug; dye; EC 1.1.1.205 (IMP dehydrogenase) inhibitor; EC 1.1.1.21 (aldehyde reductase) inhibitor; EC 1.1.1.25 (shikimate dehydrogenase) inhibitor; EC 1.6.5.2 [NAD(P)H dehydrogenase (quinone)] inhibitor; EC 1.8.1.9 (thioredoxin reductase) inhibitor; EC 2.7.10.2 (non-specific protein-tyrosine kinase) inhibitor; EC 3.5.1.98 (histone deacetylase) inhibitor; flavouring agent; food colouring; geroprotector; hepatoprotective agent; immunomodulator; iron chelator; ligand; lipoxygenase inhibitor; metabolite; neuroprotective agent; nutraceutical; radical scavenger |
| biselyngbyaside | biselyngbyaside: antineoplastic from the marine cyanobacterium Lyngbya sp.; structure in first source | ||
| alpha-cyclopiazonic acid | alpha-cyclopiazonic acids |