View source for Actin

<StructureSection load='3hbt' size='450' side='right' scene='43/430015/Cv/3' caption='Native G-actin with methyl-histidine complex with ATP, sulfate and Ca+2 ion (green) [[3hbt]]'>

== Function ==

[[Actin]] is a protein found in all eukaryotic cells.<ref>PMID:11474115</ref>  It is the monomer of two types of filaments: microfilaments which are part of the cytoskeleton and thin filaments which are part of muscles.  Three isoforms of actin are identified: α (Aa) (or G-actin) found in muscle tissue, β (Ab) and γ (Ag) actins  are components of the cytoskeleton.  F-actin is Aa bound to ATP.  For more details see:<br /> *[[F-actin]]<br /> *[[Non-polymerizable monomeric actin]].<br /> <scene name='Actin/Cv/2'>Click here to see the difference between 2 conformations of bovine Ag actin</scene> (PDB entries [[1hlu]] and [[2btf]]; morph was taken from [http://molmovdb.org/cgi-bin/movie.cgi Gallery of Morphs] of the [http://molmovdb.org Yale Morph Server]).  Actin participates in muscle contraction, cell motility, cell division and cytokinesis.  Actin associated with myosin is responsible for most cell movements.
*'''α actin''' is found exclusively in muscle fibres.<br />
*'''β actin''' is required for early embryonic development<ref>PMID:21900491</ref>.<br />
*'''γ actin''' is required for cytoskeletal maintenance<ref>PMID:19497859</ref>.

See also [[Actin Protein (Hebrew)]]

== Disease ==

Mutations in α-actin found in skeletal striated muscles can cause myopathy.  Mutations in α-actin found in smooth muscles can cause thoracic aortic aneurism. Mutations in α-actin found in heart muscles can cause heart malfunctioning. 

== Structural highlights ==

<scene name='43/430015/Cv/10'>Actin binds ATP</scene> in a cleft. Water molecules are shown as red spheres. <scene name='43/430015/Cv/13'>ATP and Ca2+ ion are located in cleft</scene>.  <scene name='43/430015/Cv/11'>Click here to see Ca2+ ion coordination site</scene>.<ref>PMID:20540085</ref> It changes its conformation upon hydrolysis of its bound ATP to ADP.  Actin filaments are polar.  They are formed with all monomers having their clefts pointing in the same direction.

== 3D Structures of Actin ==
[[Actin 3D structures]]

</StructureSection>


== Reference ==
<references/>
[[Category:Topic Page]]