title: Co-activation of RanGTPase and inhibition of GTP dissociation by Ran-GTP binding protein RanBP1.
abstract: RCC1 (the regulator of chromosome condensation) stimulates guanine nucleotide dissociation on the Ras-related nuclear protein Ran. Both polypeptides are components of a regulatory pathway that has been implicated in regulating DNA replication, onset of and exit from mitosis, mRNA processing and transport, and import of proteins into the nucleus. In a search for further members of the RCC1-Ran signal pathway, we have identified proteins of 23, 45 and 300 kDa which tightly bind to Ran-GTP but not Ran-GDP. The purified soluble 23 kDa Ran binding protein RanBP1 does not activate RanGTPase, but increases GTP hydrolysis induced by the RanGTPase-activating protein RanGAP1 by an order of magnitude. In the absence of RanGAP, it strongly inhibits RCC1-induced exchange of Ran-bound GTP. In addition, it forms a stable complex with nucleotide-free RCC1-Ran. With these properties, it differs markedly from guanine diphosphate dissociation inhibitors which preferentially prevent the exchange of protein-bound GDP and in some cases were shown to inhibit GAP-induced GTP hydrolysis. RanBP1 is the first member of a new class of proteins regulating the binding and hydrolysis of GTP by Ras-related proteins.
authors.affiliation: Division for Molecular Biology of Mitosis, German Cancer Research Center, Heidelberg.
authors.forename: F R
authors.initials: FR
authors.lastname: Bischoff
authors.forename: H
authors.initials: H
authors.lastname: Krebber
authors.forename: E
authors.initials: E
authors.lastname: Smirnova
authors.forename: W
authors.initials: W
authors.lastname: Dong
authors.forename: H
authors.initials: H
authors.lastname: Ponstingl
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020931:ran GTP-Binding Protein
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C062521:RCC1 protein, human; D016601:RNA-Binding Proteins; C091775:ran-binding protein 1; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D004492:Edetic Acid; D020558:GTP Phosphohydrolases; D020931:ran GTP-Binding Protein