Filamentos de Actina, Miosina e filamentos intermediários

Actin is a contractile protein found in muscle tissue, in which it occurs in the form of filaments. Each thin filament consist of two chains of globular actin molecules, around which is twisted a strand of tropomyosin and interspersed troponin. Units of muscle fibre consist of actin and myosin filaments, which interact to bring about muscle contraction. Actin is also found in the microfilaments that form part of the cytoskeleton of all cells. Myosin is a contractile protein that interacts with actin to bring about contraction of muscle or cell movement. The type of myosin molecule found in muscle fibres consists of a tail, by which it aggregates with other myosin molecules to form so-called ‘thick filaments’; and a globular head, which has sites for the attachment of actin and ATP moleculas.