(E) 2 µM recombinant Ran, loaded with MANT-GDP was incubated with 2 mM GppNHp in buffer control, supplemented with 2 nM recombinant RCC1, 20 nM recombinant Xenopus Nup50 proteins, or RCC1 and Nup50 together. GDP to GppNHp exchanged was monitored by the decrease in MANT fluorescence of the liberated GDP-MANT. The lower panel shows the rate constant of each experimental condition with n=4 independent experiment per condition, bars represent the mean, individual data points are indicated. 