Influence of cargo size on Ran and energy requirements for nuclear protein import.
Previous work has shown that the transport of some small protein cargoes through the nuclear pore complex (NPC) can occur in vitro in the absence of nucleoside triphosphate hydrolysis. We now demonstrate that in the importin alpha/beta and transportin import pathways, efficient in vitro transport of large proteins, in contrast to smaller proteins, requires hydrolyzable GTP and the small GTPase Ran. Morphological and biochemical analysis indicates that the presence of Ran and GTP allows large cargo to efficiently cross central regions of the NPC. We further demonstrate that this function of RanGTP at least partly involves its direct binding to importin beta and transportin. We suggest that RanGTP functions in these pathways to promote the transport of large cargo by enhancing the ability of import complexes to traverse diffusionally restricted areas of the NPC.
Lyman
Susan K
SK
Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Guan
Tinglu
T
Bednenko
Janna
J
Wodrich
Harald
H
Gerace
Larry
L
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008970:Molecular Weight; D022022:Nuclear Pore / Q000378:metabolism* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D028901:alpha Karyopherins / Q000235:genetics / Q000378:metabolism; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins; D006160:Guanosine Triphosphate; D020931:ran GTP-Binding Protein