Involved in transpo across nucleus:

Large and elaborate nuclear pore complexes (NPCs) perforate the nuclear envelope in all eukaryotes. Each NPC is composed of a set of approximately 30 different proteins, or nucleoporins Proteins to be impoed (cargo molecules) to nucleus carry a nuclear localization signal (NLS) To initiate nuclear impo, most nuclear localization signals must be recognized by nuclear impo receptors called impoins Proteins similar to impoins, referred to as expoins, are involved in the expo of many macromolecules that carry nuclear expo signals The family of impoins and expoins are referred to as karyopherins Monomeric GTPase Ran is required for both nuclear impo and expo