Ran alters nuclear pore complex conformation

Transport across the nuclear membranes occurs through the nuclear pore comp lex (NPC), and is mediated by soluble transport factors including Ran, a sm all GTPase that is generally GDP-bound during import and GTP-bound for expo rt. The dynamic nature of the NPC structure suggests a possible active role for it in driving translocation. Here we show that RanGTP but not RanGDP c auses alterations of NPC structure when injected into the cytoplasm of Xeno pus oocytes, including compaction of the NPC and extension of the cytoplasm ic filaments. RanGTP caused accumulation of nucleoplasmin-gold along the le ngth of extended cytoplasmic filaments, whereas RanGDP caused accumulation around the cytoplasmic rim of the NPC. This suggests a possible role for Ra n in altering the conformation of the cytoplasmic filaments during transpor t. (C) 2000 Academic Press.