The association of Yrb1p and Yrb2p with
Xpo1p/Gsp1p-GTP is sensitive to Rna1p but resistant to excess amounts
of NES peptides. (A) GST-Gsp1p-GTP (4 μg per reaction) was
immobilized on glutathione Sepharose and incubated for 30 min at 4°C
with 5 μg of Yrb1p, 5 μg of Yrb2p, and/or 12 μg of Xpo1p, as
indicated. Bound material was washed three times and either eluted with
SDS sample buffer (lanes 1, 2, 5, 6, 8, and 9) or incubated further for
15 min at 4°C with 1 μg of Rna1p (lanes 3, 4, and 7), 10 μg of
Yrb2p (lane 10), or 10 μg of Yrb1p (lane 11), and then washed again
three times. All samples were analyzed by SDS PAGE and Coomassie blue
staining. (B) GST fusions (6 μg per reaction) to PKI-NES-2GFP
(GST-NESp)(lanes 1–6), Yrb1p (lanes 7 and 8), or Yrb2p (lanes 9 and
10) were immobilized on glutathione Sepharose and incubated for 30 min
at 4°C with 10 μg of Gsp1p-GTP and 12 μg of Xpo1p. After three
washes, the reactions were further incubated for 15 min at 4°C with
buffer alone (lanes 1, 7, and 9), with 6 μg of Yrb1p (lane 2), with 6
μg of Yrb2p (lane 3), or with the indicated amounts of peptides
corresponding to the PKI-NES (lanes 4–6, 8, and 10). After three
washes, bound material was analyzed by SDS PAGE and Coomassie blue
staining.