RECONSTITUTION IN-VITRO OF THE MOTILE APPARATUS FROM THE AMEBOID SPERM OF ASCARIS SHOWS THAT FILAMENT ASSEMBLY AND BUNDLING MOVE MEMBRANES

We have developed an in vitro motility system from Ascaris sperm, uniq ue amoeboid cells that use filament arrays composed of major sperm pro tein (MSP) instead of an actin-based apparatus for locomotion. Additio n of ATP to sperm extracts induces formation of fibers similar to 2 mu m in diameter. These fibers display the key features of the MSP cytos keleton in vivo. Each fiber consists of a meshwork of MSP filaments an d has at one end a vesicle derived from the plasma membrane at the lea ding edge of the cell. Fiber growth is due to filament assembly at the vesicle; thus, fiber elongation results in vesicle translocation, Thi s in vitro system demonstrates directly that localized polymerization and bundling of filaments can move membranes acid provides a powerful assay for evaluating the molecular mechanism of amoeboid cell motility .