Bad, a heterodimeric partner for Bcl-XL and Bcl-2, displaces Bax and promotes cell death.
To extend the mammalian cell death pathway, we screened for further Bcl-2 interacting proteins. Both yeast two-hybrid screening and lambda expression cloning identified a novel interacting protein, Bad, whose homology to Bcl-2 is limited to the BH1 and BH2 domains. Bad selectively dimerized with Bcl-xL as well as Bcl-2, but not with Bax, Bcl-xs, Mcl-1, A1, or itself. Bad binds more strongly to Bcl-xL than Bcl-2 in mammalian cells, and it reversed the death repressor activity of Bcl-xL, but not that of Bcl-2. When Bad dimerized with Bcl-xL, Bax was displaced and apoptosis was restored. When approximately half of Bax was heterodimerized, death was inhibited. The susceptibility of a cell to a death signal is determined by these competing dimerizations in which levels of Bad influence the effectiveness of Bcl-2 versus Bcl-xL in repressing death.
Pubmed ID: 7834748 RIS Download
Amino Acid Sequence | Animals | Antibodies | Apoptosis | Carrier Proteins | Cloning, Molecular | Humans | Macromolecular Substances | Mammals | Mice | Molecular Sequence Data | Proto-Oncogene Proteins | Proto-Oncogene Proteins c-bcl-2 | Recombinant Proteins | Saccharomyces cerevisiae | Sequence Homology, Amino Acid | Transfection | bcl-Associated Death Protein | bcl-X Protein