 There are many proteins that bind to microtubules, including the motor proteins kinesin and dynein, microtubule-severing proteins like katanin, and other proteins important for regulating microtubule dynamics.Recently an actin-like protein has been found in a gram-positive bacterium "Bacillus thuringiensis", which forms a microtubule-like structure called a nanotubule, involved in plasmid segregation.Other bacterial microtubules have a ring of five protofilaments.