Actinidin, the structure of the microtubules are protein, exist in two forms, namely monomer and polymer. Actin monomers is composed of a polypeptide chain spherical molecules, also called globular actin (globular actin, G - actin), made to look like a catsup. Actin polymer formation of actin filament, called fibrous actin (fibros actin, F - actin). Under the electron microscope, the F - actin by double helix, is 8 nm in diameter, the distance between screw for 37 nm. Actin is one of the most abundant protein in eukaryotic cells. In muscle cells, the actin accounted for 10% of total protein, even if in the muscle cells, the actin also accounts for the 1 ~ 5% of total protein in the cell.
Actinidin is a medium-sized protein, is composed of 375 amino acid residues, and consists of a large, highly conservative gene encoding. The molecular weight of monomer actin molecules to 43 kda, it has three binding sites. One is the ATP binding site, the other two are combined with actin binding protein binding sites.
Actinidin expression into at least six kinds of heterogeneous form, into three types of alpha, beta, gamma, depending on the isoelectric point higher animals can be intracellular actin is divided into three classes, alpha distribution in various kinds of muscle cells, beta, and gamma distribution on muscle cells, and muscle cells. There are three kinds of alpha actin (skeletal muscle, cardiac and smooth muscle), a beta actin and two kinds of gamma actin and gamma (gamma smooth muscle not smooth muscle).
