View source for Actin

Actin filaments are 7 nm fibres&nbsp;<ref>http://rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/actin.htm</ref>. They are present in both [[Muscle|muscles]] and they are a component of the [[Cytoskeleton|cytoskeleton]]. Actin is particularly concentrated under the [[Plasma membrane|plasma membrane]] of a cell.<br> 

Structure:<br> 

*Thin 
*Flexible<br>

These filaments help to maintain cell shape and are required for movement on the cell surface. 

Actin hydrolyzes [[ATP|ATP]] to [[ADP|ADP]] when [[ATP|ATP]] is bound to the [[Nucleotide|nucleotide]] binding site, changing the conformation of actin. Actin filaments are polarized, and facillitate the movement of cellular components.<br> 

Actin filaments can form various different structures, all with the common feature that they are cell surface projections. These structures could include [[Microvilli|microvilli]], [[Filopodia|filopodia]] or [[Lamellipodia|lamellipodia]]&nbsp;<ref>Molecular biology of the cell, 4th edition, 2002, Bruce Alberts , Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter. Page 931.</ref>.<br> 

Actin filaments can undergo nucleation and this takes place on the [[Plasma membrane|plasma membrane]]. This reaction is catalysed by several [[Proteins|proteins]], one of these know as [[ARP|ARP]]. This complex causes rapid elongation at the plus end of the actin, as it nucleates actin filament growth from the minus end. The reason this process occurs is to allow a cell to change shape, in order for it respond to changes within the external environment&nbsp;<ref>Molecular biology of the cell, 4th edition, 2002, Bruce Alberts , Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter. Page 931-932.</ref>. 

Also see [[actin filaments|actin filaments]]

=== Reference  ===

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