A. Top-left panel, structure of the BH3-in-groove dimer (PDB entry 4BDU) with the predicted MOM-engaging residues presented in stick form. Bottom-left panel, structure of the BH3-in-groove dimer with the predicted protein-buried residues presented in stick form. Top-right panel, structure of the BH3-in-groove dimer without helix α5 (modified from PDB entry 4BDU), and bottom-right panel, structure of α5 (extracted from the NMR structure of Bax monomer, PDB entry 1F16). In both structures in the right panels, the residues that are buried in the MOM or exposed to the aqueous milieu as the IASD labeling data in (B-D) confirmed are presented in yellow or cyan stick form, respectively. In all panels, the color codes for the two monomers are the same as that in Figure 1A, and indicated. 