importin 9 (Ran-binding protein 9, RanBP9, HSPC273, IPO9, IMP9, KIAA1192)
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Function
- nuclear protein import as nuclear transport receptor
- receptor for nuclear localization signals (NLS) in cargo substrates
- thought to mediate docking of importin/substrate complex to the nuclear pore complex through binding to nucleoporin
- the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism
- at the nucleoplasmic side of the nuclear pore complex, Ran binds to the importin, the importin/substrate complex dissociates & importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran
- directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- & GDP-bound forms of Ran between the cytoplasm & nucleus
- mediates nuclear import of H2B histone (putative), RPS7 & RPL18A
- prevents cytoplasmic aggregation of RPS7 & RPL18A by shielding exposed basic domains
- may also import H2A, H3, H4 histones (putative), RPL4 & RPL6
- binds with high affinity to RPS7 & RPL18A
- binding is coupled to RanGTP cycles
- may bind H2A, H3, H4 histones, RPL4 & RPL6 with low affinity
- interacts with PPP2R1A & PPP2R1B
Structure
- belongs to the importin beta family
- contains 1 importin N-terminal domain
Compartment
Notes
- one of two Ran-binding protein 9
- Ran-binding protein M is the other
More general terms
Additional terms
- importin complex (NLS-binding protein)
- Ran-binding protein M; Ran-binding protein 9; RanBP9; BPM-L; BPM90; RanBPM; RanBP7 (RANBP9, RANBPM)