Bak

Bak (BCL-2 homologous antagonist/killer) is a pro-apoptotic Bcl-2 family effector that executes intrinsic apoptosis by permeabilizing the mitochondrial outer membrane together with Bax^[1]. Mechanistically, Bak activation enables mitochondrial outer membrane permeabilization, cytochrome c release, caspase activation, and apoptotic cell death^[2]. In cancer-related models, dysregulated Bcl-2 family signaling supports apoptosis evasion, while Bak/Bax-dependent mitochondrial permeabilization remains a central checkpoint for therapeutic apoptosis induction^[3]. Compared with Bax, Bak shows distinct regulatory behavior inside living cells, because Bcl-2 family interactome analysis indicates differences in Bax and Bak activation by anti-apoptotic and BH3-only proteins^[4]. Bak also differs from Bax in mitochondrial targeting biology, since VDAC2 brings both effectors to mitochondria and forms a defined VDAC2-Bak complex that can modulate Bak apoptotic activity^[5]. For experimental applications, large unilamellar vesicles provide a tractable biochemical model to test Bcl-2 family protein combinations and real-time membrane permeabilization by Bak/Bax-centered mechanisms^[6]. Pharmacologically, interfaces regulating Bak activity may be targeted to inhibit excessive Bak-mediated apoptosis or promote Bak-mediated apoptosis for cancer therapy^[5]. Small-molecule or peptide strategies that modulate Bcl-2 family interactions therefore remain practical tools for studying Bak-dependent mitochondrial apoptosis^[3][6].