Structural highlights
Function
[IMA2_MOUSE] Functions in nuclear protein import as an adapter protein for nuclear receptor KPNB1. Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta and the three components separate and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Importin-alpha is the nuclear import receptor that recognizes cargo proteins carrying conventional basic monopartite and bipartite nuclear localization sequences (NLSs) and facilitates their transport into the nucleus. Bipartite NLSs contain two clusters of basic residues, connected by linkers of variable lengths. To determine the structural basis of the recognition of diverse bipartite NLSs by mammalian importin-alpha, we co-crystallized a non-autoinhibited mouse receptor protein with peptides corresponding to the NLSs from human retinoblastoma protein and Xenopus laevis phosphoprotein N1N2, containing diverse sequences and lengths of the linker. We show that the basic clusters interact analogously in both NLSs, but the linker sequences adopt different conformations, whereas both make specific contacts with the receptor. The available data allow us to draw general conclusions about the specificity of NLS binding by importin-alpha and facilitate an improved definition of the consensus sequence of a conventional basic/bipartite NLS (KRX10-12KRRK) that can be used to identify novel nuclear proteins.
Structural basis for the specificity of bipartite nuclear localization sequence binding by importin-alpha.,Fontes MR, Teh T, Jans D, Brinkworth RI, Kobe B J Biol Chem. 2003 Jul 25;278(30):27981-7. Epub 2003 Apr 14. PMID:12695505[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Fontes MR, Teh T, Jans D, Brinkworth RI, Kobe B. Structural basis for the specificity of bipartite nuclear localization sequence binding by importin-alpha. J Biol Chem. 2003 Jul 25;278(30):27981-7. Epub 2003 Apr 14. PMID:12695505 doi:10.1074/jbc.M303275200
