Besides the motor proteins above, there are many more types of proteins capable of generating forces and torque in the cell. Many of these molecular motors are ubiquitous in both prokaryotic and eukaryotic cells, although some, such as those involved with cytoskeletal elements or chromatin, are unique to eukaryotes.  The motor protein prestin, expressed in mammalian cochlear outer hair cells, produces mechanical amplification in the cochlea.  It is a direct voltage-to-force converter, which operates at the microsecond rate and possesses piezoelectric properties.