Nuclear localization signal binding protein from Arabidopsis mediates nuclear import of Agrobacterium VirD2 protein.
T-DNA nuclear import is a central event in genetic transformation of plant cells by Agrobacterium. Presumably, the T-DNA transport intermediate is a single-stranded DNA molecule associated with two bacterial proteins, VirD2 and VirE2, which most likely mediate the transport process. While VirE2 cooperatively coats the transported single-stranded DNA, VirD2 is covalently attached to its 5' end. To better understand the mechanism of VirD2 action, a cellular receptor for VirD2 was identified and its encoding gene cloned from Arabidopsis. The identified protein, designated AtKAPalpha, specifically bound VirD2 in vivo and in vitro. VirD2-AtKAPalpha interaction was absolutely dependent on the carboxyl-terminal bipartite nuclear localization signal sequence of VirD2. The deduced amino acid sequence of AtKAPalpha was homologous to yeast and animal nuclear localization signal-binding proteins belonging to the karyopherin alpha family. Indeed, AtKAPalpha efficiently rescued a yeast mutant defective for nuclear import. Furthermore, AtKAPalpha specifically mediated transport of VirD2 into the nuclei of permeabilized yeast cells.
Ballas
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Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, NY 11794-5215, USA.
Citovsky
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D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D012231:Rhizobium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D037521:Virulence Factors
D001426:Bacterial Proteins; D018076:DNA, Complementary; C075564:NOLC1 protein, human; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010750:Phosphoproteins; D037521:Virulence Factors