Ran-binding protein 5 (RanBP5) is related to the nuclear transport factor importin-beta but interacts differently with RanBP1.
We report the identification and characterization of a novel 124-kDa Ran binding protein, RanBP5. This protein is related to importin-beta, the key mediator of nuclear localization signal (NLS)-dependent nuclear transport. RanBP5 was identified by two independent methods: it was isolated from HeLa cells by using its interaction with RanGTP in an overlay assay to monitor enrichment, and it was also found by the yeast two-hybrid selection method with RanBP1 as bait. RanBP5 binds to RanBP1 as part of a trimeric RanBP1-Ran-RanBP5 complex. Like importin-beta, RanBP5 strongly binds the GTP-bound form of Ran, stabilizing it against both intrinsic and RanGAP1-induced GTP hydrolysis and also against nucleotide exchange. The GAP resistance of the RanBP5-RanGTP complex can be relieved by RanBP1, which might reflect an in vivo role for RanBP1. RanBP5 is a predominantly cytoplasmic protein that can bind to nuclear pore complexes. We propose that RanBP5 is a mediator of a nucleocytoplasmic transport pathway that is distinct from the importin-alpha-dependent import of proteins with a classical NLS.
Deane
R
R
Abteilung Molekulare Biologie der Mitose, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Schäfer
W
W
Zimmermann
H P
HP
Mueller
L
L
Görlich
D
D
Prehn
S
S
Ponstingl
H
H
Bischoff
F R
FR
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000737:chemistry; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D016415:Sequence Alignment; D028901:alpha Karyopherins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein
D005656:Fungal Proteins; C107940:IPO5 protein, human; D009687:Nuclear Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins; C568791:importin alpha4, mouse; C091775:ran-binding protein 1; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020931:ran GTP-Binding Protein