Coprecipitation of ETs with Dsg1. (a) Immunoprecipitation followed by immunoblotting. Incubation of ETB (marked with a FLAG epitope tag) and ETD with Dsg1 showed coprecipitation at 1 minute that was markedly diminished at 60 minutes, after increased cleavage of Dsg1. Similar results were found for ETA (data not shown). (b) Binding of Dsg1 with ETA Cmu and ETA Amu. ETA Cmu, which slowly cleaves Dsg1, showed decreased binding with time. (c) ETA and ETB (marked with His epitope tags) bind to Dsg1 but not Dsg3. These ETs did not cleave or bind to Dsg3, which is highly homologous in amino acid sequence to Dsg1. Similar results were found with ETD (data not shown). IP, immunoprecipitation; IB, immunoblot.