 The entry and exit of large molecules from the nucleus is tightly controlled by the nuclear pore complexes . Although small molecules can enter the nucleus without regulation , macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit . " Cargo " proteins that must be translocated from the cytoplasm to the nucleus contain short amino acid sequences known as nuclear localization signals , which are bound by importins , while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins . The ability of importins and exportins to transport their cargo is regulated by GTPases , enzymes that hydrolyze the molecule guanosine triphosphate to release energy . The key GTPase in nuclear transport is Ran , which can bind either GTP or GDP ( guanosine diphosphate ) , depending on whether it is located in the nucleus or the cytoplasm . Whereas importins depend on RanGTP to dissociate from their cargo , exportins require RanGTP in order to bind to their cargo . 
 The entry and exit of large molecules from the nucleus is tightly controlled by the nuclear pore complexes . Although small molecules can enter the nucleus without regulation , macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit . " Cargo " proteins <a href='null_relcl' title='1'><mark>that</mark></a>must be translocated from the cytoplasm to the nucleus contain short amino acid <a href='uninflect' title='2'><mark>sequences</mark></a> known as nuclear localization signals , which are bound by importins , while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins . The ability of importins and exportins to transport their cargo is regulated by GTPases , enzymes <a href='null_relcl' title='3'><mark>that</mark></a><a href='uninflect' title='4'><mark>hydrolyze</mark></a> the molecule guanosine triphosphate to release energy . The key GTPase in nuclear transport <a href='drop_aux' title='5'><mark>is</mark></a>Ran , which can bind either GTP or GDP ( guanosine diphosphate ) , depending on whether it is located in the nucleus or the cytoplasm . Whereas importins depend on RanGTP to dissociate from their cargo , exportins require RanGTP in order to bind to their cargo . 
Da entry and exit of bigass molecules from tdanucleus is tightly controlled by the nuclear pore complexes . Although small molecules can enter the nucleus without regulation , macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit . " Cargo " proteins must be translocated from the cytoplasm to thdaucleus contain short amino acid sequence known as nuclear localization signals , which r bound by importins , while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins . Thedaility of importins and exportins to transport their cargo is regulated by GTPases , enzymes hydrolyzed the molecule guanosine triphosphate to release energy . The da GTPase in nuclear transport Ran , which can bind either GTP or GDP ( guanosine diphosphate ) , depending on whether it is located in the ndaeus or the cydalasm . Whereas importins depend on RanGTP to dissociate from their cargo , exportins require RanGTP in order to bind to their cargo .