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MOUSE IMPORTIN ALPHA-NUCLEOPLASMIN NLS PEPTIDE COMPLEXMOUSE IMPORTIN ALPHA-NUCLEOPLASMIN NLS PEPTIDE COMPLEX
Structural highlights
Function[NUPL_XENLA] Core histones chaperone involved in chromatin reprogramming, specially during fertilization and early embryonic development. Nucleoplasmin is an acidic protein which is able to assemble nucleosomes by binding histones and transferring them to DNA. [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 PubMedImportin-alpha is the nuclear import receptor that recognizes cargo proteins which contain classical monopartite and bipartite nuclear localization sequences (NLSs), and facilitates their transport into the nucleus. To determine the structural basis of the recognition of the two classes of NLSs by mammalian importin-alpha, we co-crystallized an N-terminally truncated mouse receptor protein with peptides corresponding to the monopartite NLS from the simian virus 40 (SV40) large T-antigen, and the bipartite NLS from nucleoplasmin. We show that the monopartite SV40 large T-antigen NLS binds to two binding sites on the receptor, similar to what was observed in yeast importin-alpha. The nucleoplasmin NLS-importin-alpha complex shows, for the first time, the mode of binding of bipartite NLSs to the receptor. The two basic clusters in the NLS occupy the two binding sites used by the monopartite NLS, while the sequence linking the two basic clusters is poorly ordered, consistent with its tolerance to mutations. The structures explain the structural basis for binding of diverse NLSs to the sole receptor protein. Structural basis of recognition of monopartite and bipartite nuclear localization sequences by mammalian importin-alpha.,Fontes MR, Teh T, Kobe B J Mol Biol. 2000 Apr 14;297(5):1183-94. PMID:10764582[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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