actin

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actin,

a protein abundantly present in many cells, especially muscle cells, that significantly contributes to the cell's structure and motility. Actin can very quickly assemble into long polymer rods called microfilaments. These microfilaments have a variety of roles—they form part of the cell's cytoskeleton, they interact with myosinmyosin
, one of the two major protein constituents responsible for contraction of muscle. In muscle cells myosin is arranged in long filaments called thick filaments that lie parallel to the microfilaments of actin.
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 to permit movement of the cell, and they pinch the cell into two during cell division. In muscle contraction, filaments of actin and myosin alternately unlink and chemically link in a sliding action. The energy for this reaction is supplied by adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
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.
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actin

[′ak·tən]
(biochemistry)
A muscle protein that is the chief constituent of the Z-band myofilaments of each sarcomere.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Rods also contain thin filament proteins, such as actin, myotilin, and NEB.
Thin Filaments. The thin filaments are connected to the Zline, extend perpendicularly towards the M-line and along the length of the fiber, interdigitated with the thick filaments (Hopkins).
The length regulation of the thin filaments is carried out largely by the capping proteins, CapZ and tropomodulin (Tmod).
Nebulin is a giant protein (600-900 kDa) that is also part of the thin filaments. It has a highly repetitive structure, as up to 97 % of the polypeptide consists in modules of 30-35 amino acids arranged in simple or super repeats (Donner et al., 2004; Pappas et al.).
(1970) Three-dimensional reconstructions of Factin, thin filaments and decorated thin filaments.
(1972) Effect of calcium ions on the flexibility of reconstituted thin filaments of muscle studied by quasi-elastic scattering of laser light.
(1985) Three-dimensional image analysis of the complex of thin filaments and myosin molecules from skeletal muscle.
In cervicitis, the TN bands were thickened in the basement membrane, and the protein was also present in the adjacent stroma in the form of thin filaments (Figure 1, B).
In the folded contractile layer of coelomyarian muscle, the dense bodies connect the thin filaments perpendicularly to the basal lamina, as in platymyarian muscle, but most of the basal lamina is in the form of a longitudinal ribbon that extends radially inwards between the cells [ILLUSTRATION FOR FIGURE 1 OMITTED].
Hence, the links between thin filaments and the cuticle are the same in the two types, but with the radial extension of the basal lamina in coelomyarian muscle.
When the fiber receives a signal to contract, the thick filaments pull the combs together by "rowing" against the thin filaments. Globular ends of the myosin protein stick out toward the actin and act as little paddles.
Myosin binding-induced cooperative activation of the thin filament in cardiac myocytes and skeletal muscle fibers.