| Type: | Conserved_site | Name: | Actin, conserved site |
| Description: | Actin [, ] is a ubiquitous protein involved in the formation of filamentsthat are major components of the cytoskeleton. These filaments interact with myosin to produce a sliding effect, which is the basis of muscularcontraction and many aspects of cell motility, including cytokinesis. Each actin protomer binds one molecule of ATP and has one high affinity site foreither calcium or magnesium ions, as well as several low affinity sites. Actin exists as a monomer in low salt concentrations, but filaments formrapidly 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 actinloses its ability to polymerise. It has been shown that an ATPase domain of actin shares similarity with ATPase domains of hexokinase and hsp70proteins [, ].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-exists in most cell types as components of the cytoskeleton and as mediators of internal cell motility. In plants there are many isoforms which are probably involved in a variety of functions such as cytoplasmic streaming, cell shape determination, tip growth, graviperception, cell wall deposition, etc. | Short Name: | Actin_CS |
