Actin

Actin is a ubiquitous globular protein that is one of the most highly-conserved proteins known. It is found in two main states: G-actin is the globular monomeric form, whereas F-actin forms helical polymers. Both G- and F-actin are intrinsically flexible structures - a feature vital in actin's role as a dynamic filament network.

Actin has four major functions. Firstly, F-actin polymers form microfilaments - polar intracellular 'tracks' for kinesin motor proteins, allowing the transport of vesicles, organelles and other cargo. Actin is a component of the cytoskeleton and links to α-actinin, E-cadherin and β-catenin at adherens junctions. This gives mechanical support to cells and attaches them to each other and the extracellular matrix. In muscle cells, actin-rich thin filaments associate with myosin-rich thick filaments to form actomyosin myofibrils. Using energy from the hydrolysis of ATP, myofibrils undergo cyclic shortening through actin-myosin head interactions, which represents the mechanics of muscle contraction. Finally, actin has a role in cell motility through polymerization and depolymerization of fibrils.

Actin Gene Data