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Troponin (Tn), is a key protein complex in the regulation of striated muscle contraction, composed of three subunits. The TnI subunit inhibits actomyosin ATPase, the TnT subunit binds tropomyosin and TnC, while the TnC subunit binds calcium and overcomes the inhibitory action of the troponin complex on actin thin filaments.
Troponin T (blue) anchors the complex on tropomyosin. Troponin is found in both skeletal muscle and cardiac muscle, but the specific versions of troponin differ between types of muscle. The main difference is that the TnC subunit of troponin in skeletal muscle has four calcium ion-binding sites, whereas in cardiac muscle there are only three ...
The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. [1] According to the sliding filament theory, the myosin ( thick filaments ) of muscle fibers slide past the actin ( thin filaments ) during muscle contraction, while the two groups of filaments ...
The two main myofilaments in cardiac (and skeletal) muscle are actin and myosin. Ca 2+ binds to a protein called troponin, which is bound to the actin filament. This binding causes a shape change in the troponin which exposes areas on the actin, to which the head of the myosin filament binds.
Cardiac sarcomere structure, featuring troponin T. Cardiac muscle troponin T (cTnT) is a protein that in humans is encoded by the TNNT2 gene. [5] [6] Cardiac TnT is the tropomyosin-binding subunit of the troponin complex, which is located on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
Troponin T binds to tropomyosin and helps position it on actin, [2] and together with the rest of the troponin complex, modulates contraction of striated muscle. [3] The cardiac subtype of troponin T is especially useful in the laboratory diagnosis of heart attack because it is released into the blood-stream when damage to heart muscle occurs. [4]