A ToxR-based dominant-negative system to investigate heterotypic transmembrane domain interactions

The ToxR transcription activator system is a genetic tool widely used to examine ltomotypic interactions of α-helical transmembrane domains that drive or support oligomerization of integral membrane proteins. Here, we present a variant of this system that was developed to investigate heterotypic interactions. In this system, a hontotypically interacting transmembrane domain within the ToxR protein is coespressed with a potential competitor that is embedded within an inactivated ToxR mutant. Successful heterotypic interaction competes with homotypic interaction in a dominant-negative fashion as revealed by reduced reporter gene transcription. We expect that this system will be useful for the characterization of transmembrane domains whose homotypic and heterotypic interactions compete with each other.