Find the word definition

Wiktionary
motor protein

n. (context protein English) Any of a class of proteins that are able to move on a suitable substrate, being powered by the hydrolysis of ATP, and are involved in the conversion of chemical energy into mechanical work.

Wikipedia
Motor protein

Motor proteins are a class of molecular motors that are able to move along the surface of a suitable substrate. They convert chemical energy into mechanical work by the hydrolysis of ATP. Flagellar rotation, however, is powered by a proton pump.