An optimized high-yield protocol for expression and purification of monomeric full-length BAX protein

Diverse developmental signals and pro-death stresses converge on regulation of the mitochondrial pathway of apoptosis. BAX, a pro-apoptotic BCL-2 effector, directly forms proteolipid pores in the outer mitochondrial member to activate the mitochondrial pathway of apoptosis. BAX is a viable pharmacological target for various human diseases, and increasing efforts have been made to study the molecular regulation of BAX and identify small molecules selectively targeting BAX. However, generating large quantities of monomeric and functionally-competent BAX has been challenging due to its aggregation-prone nature. Additionally, there is a lack of detailed and instructional protocols available for investigators who are not already familiar with recombinant BAX production. Here, we present a comprehensive high-yield protocol for expressing, purifying, and storing functional recombinant BAX protein. We utilize an intein-tagged BAX construct and employ a two-step chromatography strategy to capture and purify BAX, and provide example standard assays to observe BAX activation. We also highlight best practices for handling and storing BAX to effectively preserve its quality, shelf-life, and function.