Abstract
CRM1/Exportin1 mediates the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES) by forming a cooperative ternary complex with the NES-bearing substrate and the small GTPase Ran. We present a structural model of human CRM1 based on a combination of X-ray crystallography, homology modeling, and electron microscopy. The architecture of CRM1 resembles that of the import receptor transportin1, with 19 HEAT repeats and a large loop implicated in Ran binding. Residues critical for NES recognition are identified adjacent to the cysteine residue targeted by leptomycin B (LMB), a specific CRM1 inhibitor. We present evidence that a conformational change of the Ran binding loop accounts for the cooperativity of Ran- and substrate binding and for the selective enhancement of CRM1-mediated export by the cofactor RanBP3. Our findings indicate that a single architectural and mechanistic framework can explain the divergent effects of RanGTP on substrate binding by many import and export receptors.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.