Actin Antibody Available in Imgenex now
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by: Stephen Jones
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Word Count: 498
Actin is a ubiquitous protein
involved in the formation of filaments that are major components of the
cytoskeleton. It is the monomeric
subunit of microfilaments, one of the three major components of the
cytoskeleton, and of thin filaments which are part of the contractile apparatus
in muscle cells. It is the most abundant protein in the typical
eukaryotic cell, accounting for about 15% in some cell types. The protein
is highly conserved, and forms a huge variety of structure in cells in concert
with a huge numbers of actin binding proteins. The actin filaments interact
with myosin to produce a sliding effect, which is the basis of muscular
contraction and many aspects of cell motility, including cytokinesis. The
individual subunits
of actin are known as globular actin (G-actin) that assembles into
long filamentous polymers
called F-actin. Two parallel F-actin strands twist around each other in a
helical formation, giving rise to microfilaments of the cytoskeleton.
Microfilaments measure approximately 7 nm
in diameter
with a loop of the helix repeating every 37nm. Each actin protomer binds one molecule of ATP and has one high
affinity site for either calcium or magnesium ions, as well as several low
affinity sites. It exists as a monomer in low salt concentrations, but
filaments form rapidly as salt concentration rises, with the consequent
hydrolysis of ATP. Actin from many sources forms a tight complex with
deoxyribonuclease (DNase I) although the significance of this is still unknown.
The formation of this complex results in the inhibition of DNase I activity,
and actin loses its ability to polymerise. It has been shown that an ATPase
domain of actin shares similarity with ATPase domains of hexokinase and hsp70
proteins. In vertebrates there are three groups of actin isoforms: alpha, beta
and gamma. The alpha actins are found in muscle tissues and are a major
constituent of the contractile apparatus. The beta and gamma actins co-exist in
most cell types as components of the cytoskeleton and as mediators of internal
cell motility. MreB, a major component of the bacterial cytoskeleton, exhibits
high structural homology to its eukaryotic counterpart actin. Further it
has been suggested that members of the
Reference:
- Actin isoforms. Curr Opin Cell Biol. 1993 Feb;5(1):48-55 Herman IM
- The
assembly of MreB, a prokaryotic homolog of actin. The assembly of MreB, a
prokaryotic homolog of actin. J Biol
Chem. 2005 Jan 28;280(4):2628-35. Epub 2004 Nov
16
Vol. 279. no. 5350, pp. 509 – 514 Alan Hall
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