aktiin

Aktiin is a term used in some languages to denote actin, a highly conserved globular protein that polymerizes to form microfilaments and is a major component of the cellular cytoskeleton. In vertebrates, actin is a roughly 42-kilodalton protein consisting of about 375 amino acids. It exists in two main states: a monomeric globular form (G-actin) and a filamentous form (F-actin) that assembles into microfilaments essential for cell shape and movement.

Actin is encoded by several genes. In humans, major isoforms include ACTB (beta-actin), ACTG1 (gamma-actin), ACTA1 (alpha-skeletal actin), ACTA2 (alpha-smooth muscle actin), and ACTC1 (alpha-cardiac actin). These isoforms are highly conserved and differ in tissue distribution and specific roles.

Actin dynamics drive many cellular processes. G-actin binds ATP; upon polymerization, ATP is hydrolyzed and subunits are added to the growing filament. Actin filaments interact with myosin to produce muscle contraction and power non-muscle processes such as cell migration, adhesion, and cytokinesis. The cytoskeleton is regulated by a suite of actin-binding proteins (profilin, cofilin, Arp2/3, thymosin beta-4, among others) that control nucleation, elongation, branching, and turnover.

Mutations and dysregulation of actin genes are associated with diseases collectively known as actinopathies, including certain myopathies and cardiomyopathies, as well as developmental disorders. Research on aktin contributes to understanding cellular mechanics, muscle physiology, and disease mechanisms.