{PDOC50166}
{PS50166; IMPORTIN_B_NT}
{BEGIN}
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* Importin-beta N-terminal domain profile *
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Nucleocytoplasmic  transport  is mediated  by large  supramolecular structures
that span the nuclear envelope called nuclear pore complexes (NPC).

Classical  import  pathway  involves  proteins containing nuclear localization
signal  (NLS).  This transport signal is recognized in the cytosol by importin
alpha.  Binding of the resulting complex to the cytoplasmic fibrils of the NPC
is  mediated  by the cytosolic factor importin beta. From there the substrate-
alpha-beta  transport  complex  move  to  a  central NPC region, where it pass
through  a  gated channel [1,2]. This import as well as the export pathway are
dependent on the GTPase cycle of Ran protein, a Ras-related GTPase.

Importin beta  proteins  contain  a  conserved region in their N terminal part
that is important for the binding of the Ran protein [3].

The eukaryotic proteins that contain such a domain are listed below:

 - Importin-beta 1 to importin-beta 3 (also known as karyopherins beta).
 - Exportin, the receptor for the leucine-rich nuclear export signal (NES).
 - Importin-alpha  re-exporter.  Mediates  importin-alpha  reexport  from  the
   nucleus to  the  cytoplasm  after import substrates have been released into
   the nucleoplasm.
 - Vertebrate RanBP7 protein and yeast homologue nonsense-mediated  mRNA decay
   protein 5 (NMD5) of unknown function.
 - Mammalian RanBP16 protein. It may function as a nuclear transport receptor.

The profile we developed covers the whole conserved region.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: April 2002 / First entry.

[ 1] Mattaj I.W., Englmeier L.
     "Nucleocytoplasmic transport: the soluble phase."
     Annu. Rev. Biochem. 67:265-306(1998).
     PubMed=9759490; DOI=10.1146/annurev.biochem.67.1.265
[ 2] Melchior F., Gerace L.
     "Two-way trafficking with Ran."
     Trends Cell Biol. 8:175-179(1998).
     PubMed=9695834
[ 3] Vetter I.R., Arndt A., Kutay U., Gorlich D., Wittinghofer A.
     "Structural view of the Ran-Importin beta interaction at 2.3 A
     resolution."
     Cell 97:635-646(1999).
     PubMed=10367892

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