Domains of Crm1 involved in the formation of the Crm1, RanGTP, and leucine-rich nuclear export sequences trimeric complex

Nuclear export of proteins containing a leucine-rich nuclear export sequenc e (NES) is mediated by a specific NES receptor known as Crm1. This protein, which is related to the karyopherin beta family, interacts directly with N ES in a RanGTP-dependent manner. To characterize the domains of Crm1 involv ed in formation of the trimeric Crm1-NES-RanGTP complex, Nand C-terminal de letion mutants of Crm1 were generated and their ability to bind NES and Ran GTP in vitro was analyzed. Our results indicate that two regions of Crm1 ar e required for the formation of the trimeric Crm1-NES-RanGTP complex, the N -terminal domain of Crm1 and the central domain of the receptor, starting a fter residue 160 with an essential region between 566 and 720, The N-termin al domain is homologous to the RanGTP-binding domain of karyopherin beta an d therefore is Likely involved in the interaction with RanGTP. Consequently , the central domain likely corresponds to the NES-binding site of Crm1. (C ) 1999 Academic Press.