Description
Actin and myosin are the two major cytoskeletal proteins implicated in cellular movements, secretion, phagocytosis, cytokinesis, exocytosis and chromosome movement. At least 6 actin isoforms have been identified by protein sequence analyses. Four actin isoforms represents the differentiation markers of muscle tissues. Actin isoforms are >90% conserved, except the N-terminal 18aa (50-60% homology).
In absence of salts, actin exists as a globular monomeric protein (G-actin). In presence of ATP, a divalent cation (Ca 2+ or Mg 2+) and high salts (KCl, NaCl or MgCl2), the G-actin polymerizes to form a fibrous or filamentous actin (F-actin) which incorporates the cation and ATP. Dialysis of the F-actin solution against water reverses the polymerization