actin

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Related to actin filament: Intermediate filament, myosin filament

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 ?
This bright aggregation of actin may be formed during bulge formation as a result of actin filament reorganization.
Maruyama, "Human T cell L-plastin bundles actin filaments in a calcium dependent manner," Journal of Biochemistry, vol.
This size coincides with the interval between neighboring actin monomers subunits on one of two strands in an actin filament. Additionally, for a single ATP hydrolysis cycle there was a random distribution of the number of steps, ranging from one to five, i.e., the 5.5-nm steps were only loosely linked to the ATP hydrolysis cycle.
The long, needlelike sperm from the Friday Harbor population possessed a deep, narrow nuclear fossa with a long rod of actin filaments that stained brightly in both intact and acrosome-reacted sperm (see Fig.
The neck of myosin molecule plays a vital role in cellular movement and acts as a lever arm which amplifies the small conformational change developed in the head by ATP hydrolysis and relatively advances the actin filament by one step.
These findings suggest that loss of Rb function prevents mitotic defects, such as the arrest of and exit from mitosis, through upregulation of the ILK-mediated assembly of actin filaments and microtubules, which would ensure cell division.
Troponin was visualized for the first time on actin filaments. (84) Two troponin molecules on the two long-pitch actin helices were shown to be staggered by ~27.3[Angstrom] along the actin filament, and indicated by hard brackets in Figs.
N: nucleus; Nu: nucleolus; AC: actin filaments; V: microvilli; M: mitochondria; PL: primary lysosome; SL: secondary lysosome; rER: rough endoplasmic reticulum; G: Golgi bodies; B: cell blebs; P: cell processes; IF: nuclear membrane infolding; EV: endocytotic vacuole.