The BH-3 domain of Bim is required for its association with both Bcl-2 and Bax. Western blot analysis was performed with anti-Bcl-2 antibody (upper panels) or anti-Bax antibody (lower panels). Lanes 1 and 5, control from BimAD-TAPtag and BimS-TAPtag, respectively, after TAP tag purification; lanes 2 and 6, G156E mutants are impaired in their binding to both Bcl-2 and Bax; lanes 3 and 7, G156A mutants retain binding to Bcl-2 but not to Bax; lanes 4 and 8, N160A mutants retain binding to Bax but not to Bcl-2.