A GENETIC SYSTEM BASED ON SPLIT-UBIQUITIN FOR THE ANALYSIS OF INTERACTIONS BETWEEN MEMBRANE-PROTEINS IN-VIVO

A detection system for interactions between membrane proteins in vivo is described, The system is based on split-ubiquitin [Johnsson, N, & V arshavsky, A. (1994) Proc. Natl, Acad, Sci, USA 91, 10340-10344]. Inte raction between two membrane proteins is detected by proteolytic cleav age of a protein fusion, The cleavage releases a transcription factor, which activates reporter genes in the nucleus. As a result, interacti on between membrane proteins can be analyzed by the means of a colorim etric assay, We use membrane proteins of the endoplasmic reticulum as a model system, Wbp1p and Ost1p are both subunits of the oligosacchary l transferase membrane protein complex. The Alg5 protein also localize s to the membrane of the endoplasmic reticulum, but does lot interact with the oligosaccharyltransferase. Specific interactions are detected between Wbp1p and Ost1p, but not between Wbp1p and Alg5p, The new sys tem might be useful as a genetic and biochemical tool for the analysis of interactions between membrane proteins in vivo.