ABSTRACT
This chapter describes that large-scale cell movements are driven by the cytoskeleton: a cohesive meshwork of protein filaments extending throughout the cytoplasm of plant and animal cells. The cytoskeleton is the primary determinant of cell shape and movement and to this end it operates according to its own functional 'logic' or set of rules. During the polymerization of cytoskeletal filaments, actin, tubulin, or intermediate filament protein molecules, freely soluble in the cytosol, interact with the ends of their cognate protein filaments at rates that are limited only by diffusion. A cytoskeleton is one of the features, like mitochondria or the nucleus, that distinguishes eucaryotic cells from procaryotic cells. A paradoxical consequence of such manipulations when applied to cytoskeletal proteins is that gene removal often has little effect. The chapter concludes that the machinery of cell movement is located principally outside the nucleus and major membrane-bound organelles; it is left behind after soluble components are extracted.
