Actin filaments: Difference between revisions

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Actin filaments are the thinnest of the three components of the [[Cytoskeleton|cytoskeleton]] in respect to its diameter (measuring 7-8nm in diameter in stained sections of muscle cells) and thus, makes it the most flexible. It is required for the movement on the surface of the [[Cell|cells]] and also to maintain the shape of the [[Cell|cell]], through a hign concentration of actin filaments beneath the cell membrane known as the cell cortex. They are found in cells such as [[Microvilli|microvilli]], [[Filopodia|filopodia]] as well as contractile bundles, the [[Plasma membrane|plasma membrane]] and also [[Muscle cell|muscle cells]]. In some preparations they are arranged in rosettes around myosin filaments; however they are most often gathered into bundles or cables,which are many microns long and often merge or branch and terminate by penetrating into a dense body/dense band.  
The protein actin is abundant in all eukaryotic cells. It was first discovered in skeletal muscle, where actin filaments slide along filaments of another protein called myosin to make the cells contract. (In nonmuscle cells, actin filaments are less organized and myosin is much less prominent.) Actin filaments are made up of identical actin proteins arranged in a long spiral chain. Like microtubules, actin filaments have plus and minus ends, with more ATP-powered growth occurring at a filament's plus end.


Actin filament is a polymer made by polymerisation of actin monomers by hydrolysis of [[ATP|ATP]]. The filament is polarised and the monomers are more readily added to the positive side of the filament. And polymerisation is also regulated by different set of binding proteins such as bundle protein, cross linked protein, motor proteins etc.
In many types of cells, networks of actin filaments are found beneath the cell cortex, which is the meshwork of membrane-associated proteins that supports and strengthens the plasma membrane. Such networks allow cells to hold — and move — specialized shapes, such as the brush border of microvilli. Actin filaments are also involved in cytokinesis and cell movement.
 
Actin is an abundant protein in typical animal cells and accounts for arround 5% of all proteins in the cell. Half of this can be found in filaments and the other half remains as monomers in the [[Cytosol|cytosol]] of the cell.  
 
The actin filament's motor proteins are the myosin. [[Myosin|Myosin]] have a head and a tail, the head binds to the actin filament and the tail is bound to [[Plasma membrane|plasma membrane]], [[Vesicles|vesicles]] and other yosin proteins. The hydrolysis of [[ATP|ATP]] drives the myosin resulting in movement.  
 
Myosin is further divided into [[Myosin 1|myosin 1]] and [[Myosin 2|myosin 2]].
 
Also see [[Actin|actin]]

Revision as of 18:34, 28 November 2013

The protein actin is abundant in all eukaryotic cells. It was first discovered in skeletal muscle, where actin filaments slide along filaments of another protein called myosin to make the cells contract. (In nonmuscle cells, actin filaments are less organized and myosin is much less prominent.) Actin filaments are made up of identical actin proteins arranged in a long spiral chain. Like microtubules, actin filaments have plus and minus ends, with more ATP-powered growth occurring at a filament's plus end.

In many types of cells, networks of actin filaments are found beneath the cell cortex, which is the meshwork of membrane-associated proteins that supports and strengthens the plasma membrane. Such networks allow cells to hold — and move — specialized shapes, such as the brush border of microvilli. Actin filaments are also involved in cytokinesis and cell movement.

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