Mutation to Bax beyond the BH3 domain disrupts interactions with pro-survival proteins and promotes apoptosis.

Pro-survival members of the Bcl-2 family of proteins restrain the pro-apoptotic activity of Bax, either directly through interactions with Bax or indirectly by sequestration of activator BH3-only proteins, or both. Mutations in Bax that promote apoptosis can provide insight into how Bax is regulated. Here, we describe crystal structures of ...
the pro-survival proteins Mcl-1 and Bcl-x(L) in complex with a 34-mer peptide from Bax that encompasses its BH3 domain. These structures reveal canonical interactions between four signature hydrophobic amino acids from the BaxBH3 domain and the BH3-binding groove of the pro-survival proteins. In both structures, Met-74 from the Bax peptide engages with the BH3-binding groove in a fifth hydrophobic interaction. Various Bax Met-74 mutants disrupt interactions between Bax and all pro-survival proteins, but these Bax mutants retain pro-apoptotic activity. Bax/Bak-deficient mouse embryonic fibroblast cells reconstituted with several Bax Met-74 mutants are more sensitive to the BH3 mimetic compound ABT-737 as compared with cells expressing wild-type Bax. Furthermore, the cells expressing Bax Met-74 mutants are less viable in colony assays even in the absence of an external apoptotic stimulus. These results support a model in which direct restraint of Bax by pro-survival Bcl-2 proteins is a barrier to apoptosis.
Mesh Terms:
Animals, Apoptosis, Biphenyl Compounds, Cell Survival, Cells, Cultured, Crystallography, Fibroblasts, Humans, Mice, Mitochondria, Mutagenesis, Myeloid Cell Leukemia Sequence 1 Protein, Nitrophenols, Piperazines, Protein Structure, Secondary, Protein Structure, Tertiary, Proto-Oncogene Proteins c-bcl-2, Saccharomyces cerevisiae, Sulfonamides, bcl-2-Associated X Protein
J. Biol. Chem.
Date: Mar. 04, 2011
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