We investigated the role of RanBP3, a nuclear member of the Ran‐binding protein 1 family, in CRM1‐mediated protein export in higher eukaryotes. RanBP3 interacts directly with CRM1 and also forms a trimeric complex with CRM1 and RanGTP. However, RanBP3 does not bind to CRM1 like an export substrate. Instead, it can stabilize CRM1–export substrate interaction. Nuclear RanBP3 stimulates CRM1‐dependent protein export in permeabilized cells. These data indicate that RanBP3 functions by a novel mechanism as a cofactor in recognition and export of certain CRM1 substrates. In vitro, RanBP3 binding to CRM1 affects the relative affinity of CRM1 for different substrates.
- Received June 19, 2001.
- Revision received August 21, 2001.
- Accepted August 22, 2001.
- Copyright © 2001 European Molecular Biology Organization