Photocrosslinking Approach to Investigate Protein Interactions in the BCL-2 Family.

The Bcl-2 family of proteins regulates mitochondrial outer membrane permeability thereby making life or death decisions for cells. Most of Bcl-2 proteins contain hydrophobic regions that are embedded in intracellular membranes such as mitochondria. These membrane proteins are difficult to express and purify thereby preluding biochemical and biophysical characterizations. Here, we describe a photocrosslinking approach based on in vitro synthesis of Bcl-2 proteins with photoreactive amino acid analogs incorporated at specific locations. These photoreactive proteins are reconstituted into liposomal membranes with defined phospholipids or mitochondrial membranes isolated from animals, and their interactions with other Bcl-2 proteins are detected by photocrosslinking.