Spectrin/actin complex isolated from sheep erythrocytes accelerates actin polymerization by simple nucleation. Evidence for oligomeric actin in the erythrocyte cytoskeleton.

A complex of spectrin and actin, isolated from sheep erythrocyte ghosts, accelerates the polymerization of actin in buffer containing 0.3 m~ MgC12.The rate of actin polymerization is similarly increased by sonicated F-actin nuclei.At steady state, the critical concentration of actin is lower when polymerization occurs in the presence of spectrin/actin complex than in its absence.Polymerization of actin in the presence of spectrin/actin complex is inhibited by substoichiometric concentrations of cytochalasin D, which is thought to block the net polymerizing ends of growing actin filaments (Brenner, S .L., and Korn, E. D. (