Expression and purification of full-length human Bax alpha

Bax is a proapoptotic ion channel forming protein of the Bcl-2 family. In c ells the protein is found in the cytosol and in the mitochondria membrane w here it presumably is involved during apoptosis in disruption of the mitoch ondrial membrane potential and release of cytochrome c. The protein has a h ydrophobic domain at the C-terminus, which renders it a limited solubility. Thus, all studies on recombinant Bax has so far been performed on C-termin al truncated protein. We have expressed and purified the full-length human Bax alpha. The protein was expressed with a His tag at the N-terminus and p urified by affinity chromatography on Ni-NTA-agarose followed by ion-exchan ge chromatography on Q-Sepharose, The protein was more than 98% pure on SDS -PAGE and in the presence of 1% (w/v) octyl glucoside it could be concentra ted up to 0.5 mg/ml. Full-length Bax was 25-fold more efficient, compared t o C-terminal truncated Bax, in forming ion channels and trigger carboxyfluo rescein release from liposomes. (C) 1999 Academic Press.