Figure 4 - full size

Figure 4. Figure 4. A mechanistic explanation for developmental GOF mutations in the BIR1 domain. (a) The GOF mutations retain DrICE inhibition and can no longer be regulated by the Hid peptide. Wild-type BIR1 inhibited DrICE (lane 4), and this inhibition was removed by the presence of the Hid peptide (lane 5). In contrast, the mutant proteins G88S and G88D inhibited DrICE (lanes 6 and 8), but this inhibition was not removed by Hid (lanes 7 and 9). (b) Interaction between DrICE and the mutant BIR1 proteins can no longer be weakened or disrupted by the Hid peptide. The developmental GOF mutations in the BIR1 domain (G88S and G88D) retained a stable interaction with DrICE as shown by gel filtration. The presence of Hid peptide did not affect this interaction.