Target type: cellularcomponent
The volume enclosed by the membranes of the sarcoplasmic reticulum. [GOC:rph]
The sarcoplasmic reticulum (SR) lumen is a specialized intracellular compartment within muscle cells, specifically skeletal and cardiac muscle. It is a network of interconnected tubules and cisternae that surrounds the myofibrils, the contractile units of muscle fibers. The lumen of the SR is filled with a fluid that contains a high concentration of calcium ions (Ca2+), which are essential for muscle contraction.
**Here are some detailed characteristics of the SR lumen:**
* **Calcium Store:** The SR lumen is the primary intracellular storage site for Ca2+ in muscle cells. The Ca2+ is actively pumped into the lumen by SR Ca2+-ATPase pumps, maintaining a high concentration gradient across the SR membrane.
* **Release and Uptake of Calcium:** During muscle contraction, a nerve impulse triggers the release of Ca2+ from the SR lumen into the sarcoplasm, the cytoplasm of muscle cells. This Ca2+ binds to troponin, a protein associated with the thin filaments of the myofibrils, initiating muscle contraction. Following contraction, Ca2+ is actively pumped back into the SR lumen, restoring the resting state of the muscle.
* **Specialized Proteins:** The SR lumen contains several specialized proteins involved in Ca2+ handling and regulation, including:
* **Calsequestrin:** A high-capacity Ca2+-binding protein that buffers Ca2+ in the lumen, preventing excessive accumulation.
* **Sarcolipin:** A small protein that regulates the activity of the SR Ca2+-ATPase, influencing Ca2+ uptake.
* **Junctin and Triadin:** Proteins that interact with the SR Ca2+-ATPase and ryanodine receptor, facilitating Ca2+ release and uptake.
* **Tubular Network:** The SR lumen forms a complex network of interconnected tubules, including:
* **Terminal Cisternae:** Expanded regions of the SR located at the junctions between A and I bands in the myofibrils. They are responsible for the localized release of Ca2+ during muscle contraction.
* **Longitudinal Tubules:** Run parallel to the myofibrils, connecting the terminal cisternae and facilitating Ca2+ diffusion throughout the SR network.
* **Critical Role in Muscle Contraction:** The SR lumen plays a vital role in muscle contraction by providing the rapid release and uptake of Ca2+, enabling efficient and precise control of muscle activity.
* **Structural Integrity:** The SR lumen is enclosed by a specialized membrane that maintains its structural integrity and regulates the flow of molecules between the lumen and the sarcoplasm.
* **Interactions with Other Cellular Components:** The SR lumen interacts closely with other cellular components involved in muscle contraction, including the sarcolemma (muscle cell membrane) and the transverse tubules (T-tubules), which transmit the nerve impulse to the SR.
* **Regulation of Muscle Function:** The SR lumen contributes to the regulation of muscle function by modulating Ca2+ levels and influencing the speed and duration of muscle contraction.
**In summary, the sarcoplasmic reticulum lumen is a specialized intracellular compartment critical for muscle contraction by serving as a calcium store, regulating calcium release and uptake, and interacting with other cellular components to ensure proper muscle function.**
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Protein | Definition | Taxonomy |
---|---|---|
Endoplasmin | An endoplasmin that is encoded in the genome of dog. [OMA:P41148, PRO:DAN] | Canis lupus familiaris (dog) |
Endoplasmin | An endoplasmin that is encoded in the genome of human. [PRO:DAN] | Homo sapiens (human) |
Compound | Definition | Classes | Roles |
---|---|---|---|
adenosine diphosphate | Adenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position. | adenosine 5'-phosphate; purine ribonucleoside 5'-diphosphate | fundamental metabolite; human metabolite |
2-chloroadenosine | 5-chloroformycin A: structure given in first source | purine nucleoside | |
adenosine | quinquefolan B: isolated from roots of Panax quinquefolium L.; RN not in Chemline 10/87; RN from Toxlit | adenosines; purines D-ribonucleoside | analgesic; anti-arrhythmia drug; fundamental metabolite; human metabolite; vasodilator agent |
adenosine-5'-carboxylic acid | purine nucleoside | ||
adenosine 5'-carboxamide | adenosine 5'-carboxamide: structure | ||
5'-n-methylcarboxamideadenosine | 5'-N-methylcarboxamideadenosine: RN given refers to (beta-D)-isomer | ||
n-methyladenosine | N-methyladenosine: is a inhibitor of cell differentiation N(6)-methyladenosine : A methyladenosine compound with one methyl group attached to N(6) of the adenine nucleobase. | methyladenosine | |
ethyl adenosine-5'-carboxylate | ethyl adenosine-5'-carboxylate: potent vasoactive substance; RN given refers to parent cpd | ||
adenosine 5'-phosphoramidate | adenosine 5'-phosphoramidate : The phosphoramadite analogue of AMP. | organic phosphoramidate | Mycoplasma genitalium metabolite |
adenosine-5'-(n-ethylcarboxamide) | Adenosine-5'-(N-ethylcarboxamide): A stable adenosine A1 and A2 receptor agonist. Experimentally, it inhibits cAMP and cGMP phosphodiesterase activity. N-ethyl-5'-carboxamidoadenosine : A derivative of adenosine in which the 5'-hydroxymethyl group is replaced by an N-ethylcarboxamido group. | adenosines; monocarboxylic acid amide | adenosine A1 receptor agonist; adenosine A2A receptor agonist; antineoplastic agent; EC 3.1.4.* (phosphoric diester hydrolase) inhibitor; vasodilator agent |
adenosine-5'-(N-propyl)carboxamide | adenosine-5'-(N-propyl)carboxamide : A monocarboxylic acid amide that is the propyl amide of adenosine 5'-carboxylic acid. | adenosines; monocarboxylic acid amide | |
geldanamycin | 1,4-benzoquinones; ansamycin; carbamate ester; organic heterobicyclic compound | antimicrobial agent; antineoplastic agent; antiviral agent; cysteine protease inhibitor; Hsp90 inhibitor | |
17-(dimethylaminoethylamino)-17-demethoxygeldanamycin | 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin: structure in first source alvespimycin : A 19-membered macrocyle that is geldanamycin in which the methoxy group attached to the benzoquinone moiety has been replaced by a 2-(N,N-dimethylamino)ethylamino group. | 1,4-benzoquinones; ansamycin; carbamate ester; secondary amino compound; tertiary amino compound | Hsp90 inhibitor |
tanespimycin | CP 127374: analog of herbimycin A | 1,4-benzoquinones; ansamycin; carbamate ester; organic heterobicyclic compound; secondary amino compound | antineoplastic agent; apoptosis inducer; Hsp90 inhibitor |
1-aminoadenosine | 1-aminoadenosine: structure | ||
9h-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-n-(1-methylethyl)- | 9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-: an epichaperome (purine-scaffold) inhibitor; structure in first source | ||
5'-amino-5'-deoxyadenosine | |||
ipi 493 | 17-aminogeldanamycin: structure in first source | ||
n-cyclopropyl adenosine-5'-carboxamide | |||
ec 144 | EC 144: structure in first source | ||
at 13387 | (2,4-dihydroxy-5-isopropylphenyl)-(5-(4-methylpiperazin-1-ylmethyl)-1,3-dihydroisoindol-2-yl)methanone: structure in first source onalespib : A member of the class of isoindoles that is isoindole in which the amino group has been acylated by a 2,4-dihydroxy-5-isopropylbenzoyl group and in which position 5 of the isoidole moiety has been substituted by a (4-methylpiperazin-1-yl)methyl group. A second-generation Hsp90 inhibitor. | benzamides; isoindoles; N-alkylpiperazine; resorcinols; tertiary carboxamide | antineoplastic agent; Hsp90 inhibitor |
cnf 2024 | 2-aminopurines; aromatic ether; organochlorine compound; pyridines | antineoplastic agent; Hsp90 inhibitor | |
snx 2112 | SNX 2112: an orally available small molecule Hsp90 inhibitor; structure in first source | ||
debio 0932 | CUDC 305: an Hsp90 inhibitor with antineoplastic activity; structure in first source | ||
tas-116 | |||
ver 52296 | luminespib : A monocarboxylic acid amide obtained by formal condensation of the carboxy group of 5-(2,4-dihydroxy-5-isopropylphenyl)-4-[4-(morpholin-4-ylmethyl)phenyl]-1,2-oxazole-3-carboxylic acid with the amino group of ethylamine. | aromatic amide; isoxazoles; monocarboxylic acid amide; morpholines; resorcinols | angiogenesis inhibitor; antineoplastic agent; Hsp90 inhibitor |
sta 9090 | ring assembly; triazoles |