10.2 Structure and composition of microfilament They are solid, thinner filament structures(6-8 nm, in diameter) composed of a double-helical polymer of the protein actin. And microfilaments play a key role of in virtually all types of contractility and location of cells as well as motility within cells L. Actin The most abundant protein in many eukaryocytic cells of constituting 5 or more of the total cell proteins(20% of their mass is actin in muscle cell). A typical cytosolic concentration of actin in nonmuscle cells is 0. 5mM Actin has MW 42KD with x 375 amino acid residues encoded by a large, highly conserved gene family. Some single-celled enkaryotes, e.g. yeasts and amebas have only a single actin gene, whereas many eukaryotes contain multple actin genes10.2 Structure and composition of microfilament They are solid, thinner filament structures (6-8 nm, in diameter) composed of a double-helical polymer of the protein actin. And microfilaments play a key role of in virtually all types of contractility and location of cells as well as motility within cells. 1. Actin The most abundant protein in many eukaryocytic cells, of constituting 5 % or more of the total cell proteins (20% of their mass is actin in muscle cell). A typical cytosolic concentration of actin in nonmuscle cells is 0.5mM. Actin has MW 42KD with ~ 375 amino acid residues, encoded by a large, highly conserved gene family. Some single-celled enkaryotes, e.g. yeasts and amebas have only a single actin gene, whereas many eukaryotes contain multple actin genes