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 ?
In short, for muscle contraction to be generated, the calcium released from the sarcoplasmic reticulum will bind to TnC, inducing conformational changes that alter the inhibitory action of TnI and consequently also alter the position of tropomyosin protein on actin filaments, freeing the active sites in actin filaments for the binding of myosin heavy heads, allowing the formation of cross bridges (Yanagida & Oosawa, 1975; Gordon et al.; Bekyarova et al., 2008; Lin et al.).
The second possibility is fast actin filament disassembly by proteins such as ADF/cofilin and Aipl (Bernstein & Bamburg 2010, Brieher 2013, Gressin et al.
ROCK and downstream molecules lead to the interaction of myosin motor molecules with actin filaments [36].
Defects of plastin-3 in the organization of actin filament bundles in bone cells may interfere the necessary conversion of mechanical signals to biochemical signals in osteoblasts and osteoclasts, thereby leading to osteoporosis [9].
The distance a single myosin can move during the hydrolysis of a single ATP molecule is limited to half the helical pitch of the actin filaments, as described above.
Protrusion at the leading edge is driven by actin polymerization to form a lamellipodium, which is a dynamic dendritic network with actin binding proteins such as Arp2/3 for nucleation and branching of actin filaments [22, 23], capping proteins for terminating actin polymerization [24] and ADF/cofilin for severing actin filaments [25].
The etiology of the inclusion bodies is, as of yet, unclear, but it is known that they are made up of actin filaments. Treatment options are limited, but the best approach is nonintervention because of their propensity to spontaneously regress and the complications that accompany surgery.
Sarcomere shortening would be achieved by sliding gradually towards actin filament inside the disc dark.
For example, it controls the building up and breaking down of actin filaments. These filaments are not only necessary for cell division, but also for the spreading of tumour metastases in the body.
This complex is responsible for the nucleation of new actin filaments and elongation of existing actin filaments and is thus crucial to cytoskeletal dynamics such as reorganization and polymerization.