Video Experimental Relacionado
Updated: Aug 12, 2026
10:24
Cytosolic Calcium Measurements in Renal Epithelial Cells by Flow Cytometry
Published on: October 28, 2014
El retículo sarcoplásmico contiene canales de calcio activados por nucleótidos de adenina
Nature
|August 1, 1985
Resumen
Los canales de liberación de calcio del músculo esquelético, activados por nucleótidos de adenina, facilitan el rápido eflujo de calcio desde el retículo sarcoplasmático. Estos canales exhiben una gran conductividad y selectividad para cationes divalentes.
Área de la Ciencia:
- Fisiología Muscular Fisiología Muscular
- Biología Molecular Biología Molecular
- Investigación del canal iónico.
Sus antecedentes:
- El acoplamiento de excitación y contracción en el músculo esquelético requiere un rápido eflujo de calcio desde el retículo sarcoplasmático (SR).
- Se sabe que los nucleótidos de adenina estimulan el eflujo de calcio de la SR, lo que sugiere un papel para un canal de liberación de calcio.
Objetivo del estudio:
- Para caracterizar las propiedades biofísicas del canal de liberación de calcio activado por nucleótido del retículo sarcoplasmático del músculo esquelético.
Principales métodos:
- Purificación de las membranas SR "pesadas" y inserción de proteínas SR en las bicapas lipídicas planas.
- Grabaciones de un solo canal para analizar la actividad del canal y el transporte iónico.
- Utilizó la técnica de fusión para la inserción de proteínas y caracterizó las propiedades del canal a través de mediciones de conductividad y permeabilidad.
Principales resultados:
- Se identificaron y registraron canales únicos de liberación de calcio de membranas purificadas de SR.
- Los canales fueron activados por nucleótidos de adenina y bloqueados por rutenio rojo.
- Se observó una gran conductividad (170 pS en 50 mM Ba2+) con una selectividad significativa para los cationes divalentes (P(Ba) /P(Cs) = 11.4).
Conclusiones:
- El canal identificado media el rápido eflujo de calcio, consistente con un mecanismo de difusión pasiva a través de un canal activado por nucleótidos.
- La gran conductividad y la selectividad catiónica proporcionan información biofísica crucial sobre los canales de liberación de calcio del músculo esquelético.
Videos de Conceptos Relacionados
01:26Cross-bridge Cycle
As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
01:34ATP Driven Pumps II: P-type Pumps
The P-type pumps are a large family of integral membrane transporter ATPases. They are divided into five major types based on substrate specificity, from I to V.
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
01:27Feedback Regulation of Calcium Concentration
Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
01:16Calmodulin-dependent Signaling
Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:29Relaxation of Skeletal Muscles
The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
01:25Smooth Muscle Contraction
Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...