Rational Design of Regulators of Programmed Cell Death in Human Breast Cancer
Final rept. 1 Jul 1999-30 Jun 2003
ROCKEFELLER UNIV NEW YORK
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The BH3 motif of the pro-survival family of proteins, BCL, is also present in pro-apoptotic proteins like BID and BAX. Homo and hetero-oligomerization interactions of the BH3 motif are generally recognized as the critical component of their apoptotic activities. In full length BID, the putative hydrophobic binding surface of its BH3 motif is substantially occluded by intramolecular contacts, many of which are removed on BIDs transformation to tBID by cleavage with caspase 8, required for tBID s proapoptotic action on mitochondria, thereby releasing cytochrome c. As a step to more complete characterization of the hetero-oligomeric complexes of BID and BCL family molecules, we report here the formation of a tight complex of the BH3 motif sequence of BID with BCL-XL. In contrast to the previously reported of BAK BH3 motif with BCL-XL,the BID BH3 peptide PDSESQEEIMHNIARKLAQIGDDI forms an -helix significantly extended to the N-terminus, as monitored by 15N 1H nOe determination, and by 13C chemical shifts. Modeling the BID BH3 motif BCL-XL on the basis of the previous structure shows the extended helix well fitted to an extended cavity in BCL-XL. Mutagenesis of the peptide and of BCL-XL on the basis of this model identified the key residues in the BH3 motif, but suggests that some conformational flexibility is likely in the BCL surface.
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