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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actin

[′ak·tən]
(biochemistry)
A muscle protein that is the chief constituent of the Z-band myofilaments of each sarcomere.
References in periodicals archive ?
Spearman rank correlation coefficient between BT serotonin, BT - ATP/ADP ratio, BT - [Ca.sup.2+], [Ca.sup.2+] - serotonin and [Ca.sup.2+] - F-actin Variables [r.sub.s] BT - serotonin -0.50 BT - ATP/ADP ratio 0.52 BT - [Ca.sup.2+] -0.55 [Ca.sup.2+] - serotonin 0.48 [Ca.sup.2+] - F- actin 0.57 All correlation coefficient (Spearman rho-rs) values were significant at P <0.05 BT, bleeding time; ATP, adenosine tri phosphate; ADP, adenosine di phosphate; [Ca.sup.2+], calcium; F-actin, filamentous actin
Fluorescent staining of intact sperm revealed that the extent of filamentous actin in S.
Images of confocal microscopy show that, in PEG 35 pretreated livers, filamentous actins (red) and hepatocytes morphology were better preserved when compared with nontreated ones.
Typically this independent process involves either the rapid polymerization of globular to filamentous actin to form a rod-like structure (Schroeder and Christen, 1982; Tilney, 1985), or the inter-sliding of actin filaments in a preformed rod, causing its extension, as in bivalves (Tilney, 1985; Tilney et al., 1987) and some archaeogastropods (Lewis et al., 1980; Shiroya et al., 1986; Shiroya and Sakai, 1993).
The filamentous actin network in a neuronal growth cone shows a constant retrograde flow in DIC images (1).
Staining with rhodamine phalloidin showed that these accumulations of ooplasm contained filamentous actin (F-actin, [ILLUSTRATION FOR FIGURE 1B OMITTED]).