NCIt definition : A globular subunit of microfilaments, highly conserved Actin is one of the most abundant
proteins in eukaryotic cells. Monomeric actin, a slow ATPase composed of a 375 amino
acid polypeptide chain, interacts with one molecule of ATP or ADP and contains high
affinity and low affinity binding sites for divalent cations. Actin can quickly assemble
into long microfilament polymers. In conjunction with myosin, actin is responsible
for the contraction and relaxation of muscle.;