Bax, a member of the Bcl-2 protein family, plays a critical role in apoptosis. This study investigates the movement of Bax from the cytosol to mitochondria during apoptosis. Using green fluorescent protein (GFP) fusion constructs, researchers observed that Bax remains diffusely distributed in the cytosol in healthy cells, while Bcl-2 and Bcl-XL localize to mitochondria. Upon induction of apoptosis, Bax rapidly redistributes to a punctate pattern that partially colocalizes with mitochondria. This redistribution occurs within 30 minutes of apoptosis initiation, before significant cellular changes such as shrinkage or nuclear condensation. Removal of the COOH-terminal hydrophobic domain from Bax inhibits its redistribution and its ability to promote apoptosis. These findings suggest that the movement of Bax to mitochondria is essential for its pro-apoptotic function. The study also shows that Bax is a soluble protein in healthy cells, and its localization to mitochondria is regulated by the COOH-terminal hydrophobic domain. The results indicate that Bax redistribution during apoptosis is a key event in the process of programmed cell death.Bax, a member of the Bcl-2 protein family, plays a critical role in apoptosis. This study investigates the movement of Bax from the cytosol to mitochondria during apoptosis. Using green fluorescent protein (GFP) fusion constructs, researchers observed that Bax remains diffusely distributed in the cytosol in healthy cells, while Bcl-2 and Bcl-XL localize to mitochondria. Upon induction of apoptosis, Bax rapidly redistributes to a punctate pattern that partially colocalizes with mitochondria. This redistribution occurs within 30 minutes of apoptosis initiation, before significant cellular changes such as shrinkage or nuclear condensation. Removal of the COOH-terminal hydrophobic domain from Bax inhibits its redistribution and its ability to promote apoptosis. These findings suggest that the movement of Bax to mitochondria is essential for its pro-apoptotic function. The study also shows that Bax is a soluble protein in healthy cells, and its localization to mitochondria is regulated by the COOH-terminal hydrophobic domain. The results indicate that Bax redistribution during apoptosis is a key event in the process of programmed cell death.