We consider a motor that is a Brownian particle which is permeable to molecules of the surrounding thermal bath. The molecules can flow in and out the particle. (Examples of permeable Brownian particles are micro-gels and lipid vesicles like liposomes.) When a molecule is inside the Brownian particle, it experiences a potential similar to that in transition-state theory, i.e., it is characterized by two stationary states with a finite energy difference (potential drop) separated by a potential barrier. The internal potential drop maintains the diode-like asymmetry of molecular fluxes through the particle, which results in the particle's stationary drift.