Simultaneous in vitro molecular screening of protein-peptide interactions by flow cytometry, using six Bcl-2 family proteins as examples.

The B-cell lymphoma-2 (Bcl-2) family contains six antiapoptotic members, each with a hydrophobic pocket in which Bcl-2 homology region 3 (BH3) helices bind. This binding quenches apoptotic signals from activated BH3 family members. Many tumor cells either have increased expression of one of these six proteins or become overexpressed under treatment. Six fusion proteins made up of glutathione-S-transferase and each of the Bcl-2 members are bound individually to six glutathione bead sets, each set being easily distinguished by its different intensity of red fluorescence. The coated bead sets are washed, combined and incubated with green fluorescent Bim-BH3 peptide and a small molecule in 10-μl wells for 1 h. The green fluorescence signal for each bead set is resolved, and selective inhibitors are expected to reduce the signal for individual bead sets. Each 384-well plate is analyzed in 12 min, measuring 200 of 2,000 beads (∼10%) of each type per well.