(D) GST-fusion constructs of the Xenopus Nup50 minimal NPC binding fragment (aa 144-189) comprising no or single point mutations were incubated with Xenopus egg extracts. Starting material as well as bound proteins were analyzed by Western blotting with indicated antibodies. The quantitation shows the average MEL28/ELYS and Nup153 bead bound signal from three independent experiments, normalized to the signal of their respective wild-type GST fusion Data points from individual experiments are indicated. 