2c1t
From Proteopedia
STRUCTURE OF THE KAP60P:NUP2 COMPLEX
Structural highlights
Function[IMA1_YEAST] Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Promotes docking of import substrates to the nuclear envelope. Seems to act as a cytosolic receptor for both simple and bipartite NLS motifs (By similarity).[1] [2] [3] [NUP2_YEAST] Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope (GSP1 and GSP2 GTPases associated predominantly with GTP in the nucleus, with GDP in the cytoplasm). As one of the FG repeat nucleoporins NUP2 is involved in interactions with and guidance of nuclear transport receptors such as SRP1-KAP95 (importin alpha and beta) through the NPC. Like the closely related NUP1 it also plays an important role in disassembling and recycling SRP1-KAP95 to the cytoplasm after nuclear import. Upon entry of the heterotrimeric SRP1-KAP95-cargo complex in the nucleus, NUP2 binds through its N-terminus to the SRP1 nuclear localization signal (NLS) binding site, thus accelerating the release of the NLS-cargo. SRP1 in turn is released from NUP2 by binding of the GSP1-GTP associated export factor CSE1. NUP2 may also have a chromatin boundary/insulator activity through indirect interaction with genomic DNA via CSE1 and blocking of heterochromatin spreading.[4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] 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 PubMedNuclear import of proteins containing classical nuclear localization signals (NLS) is mediated by the importin-alpha:beta complex that binds cargo in the cytoplasm and facilitates its passage through nuclear pores, after which nuclear RanGTP dissociates the import complex and the importins are recycled. In vertebrates, import is stimulated by nucleoporin Nup50, which has been proposed to accompany the import complex through nuclear pores. However, we show here that the Nup50 N-terminal domain actively displaces NLSs from importin-alpha, which would be more consistent with Nup50 functioning to coordinate import complex disassembly and importin recycling. The crystal structure of the importin-alpha:Nup50 complex shows that Nup50 binds at two sites on importin-alpha. One site overlaps the secondary NLS-binding site, whereas the second extends along the importin-alpha C-terminus. Mutagenesis indicates that interaction at both sites is required for Nup50 to displace NLSs. The Cse1p:Kap60p:RanGTP complex structure suggests how Nup50 is then displaced on formation of the importin-alpha export complex. These results provide a rationale for understanding the series of interactions that orchestrate the terminal steps of nuclear protein import. Nup50/Npap60 function in nuclear protein import complex disassembly and importin recycling.,Matsuura Y, Stewart M EMBO J. 2005 Nov 2;24(21):3681-9. Epub 2005 Oct 13. PMID:16222336[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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Categories: Saccharomyces cerevisiae | Matsuura, Y | Stewart, M | Armadillo repeat | Karyopherin recycling | Nls release | Nucear import | Nuclear pore complex | Nuclear protein | Nuclear transport-complex | Nucleoporin | Phosphorylation | Protein transport | Protein transport-membrane protein complex | Protein transport/membrane protein | Translocation
