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CRYSTAL STRUCTURE OF YEAST KARYOPHERIN (IMPORTIN) ALPHA IN COMPLEX WITH A NUP2P N-TERMINAL FRAGMENT
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 PubMedThe yeast nucleoporin Nup2p is associated primarily with the nuclear basket of nuclear pore complexes and is required for efficient importin-alpha:beta-mediated nuclear protein import as well as efficient nuclear export of Kap60p/importin-alpha. Residues 1-51 of Nup2p bind tightly to Kap60p and are required for Nup2p function in vivo. We have determined the 2.6 A resolution crystal structure of a complex between this region of Nup2p and the armadillo repeat domain of Kap60p. Nup2p binds along the inner concave groove of Kap60p, but its interaction interface is different from that employed for nuclear localization signal (NLS) recognition although there is some overlap between them. Nup2p binds Kap60p more strongly than NLSs and accelerates release of NLSs from Kap60p. Nup2p itself is released from Kap60p by Cse1p:RanGTP only in the presence of the importin-beta binding (IBB) domain of Kap60p. These data indicate that Nup2p increases the overall rate of nuclear trafficking by coordinating nuclear import termination and importin recycling as a concerted process. Structural basis for Nup2p function in cargo release and karyopherin recycling in nuclear import.,Matsuura Y, Lange A, Harreman MT, Corbett AH, Stewart M EMBO J. 2003 Oct 15;22(20):5358-69. PMID:14532109[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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