The cytoskeleton is a dynamic network of interlinking protein filaments found in the cytoplasm of all cells. The primary function of the cytoskeleton is to give the cell shape and it also plays a role in cell protection, cell motility, cytokinesis, intracellular transport, cell division and organization of the organelles within the cell. In eukaryotes, is composed of three main components, actin filaments (microfilaments), intermediate filaments and microtubules. Each is formed by the polymerization of protein subunits and all are capable of rapid growth or disassembly depending on organism and cell type.
Motor proteins are the force behind muscle contraction and also the active transport of many proteins and vesicles in the cytoplasm. They are a class of molecular motors that are able to move along the surface of a suitable substrate, powered by the hydrolysis of ATP. There are three superfamilies of cytoskeletal motor proteins – myosin motors, which act upon actin filaments to generate cell surface contractions, as well as vesicle motility, cytoplasmic streaming and muscle cell contraction, and kinesin and dynein microtubule based motor superfamilies which move vesicles and organelles within cells, cause the beating of flagella and cilia, and act within the mitotic and meiotic spindles to segregate replicated chromosomes.