Endoplasmic reticulum exit sites (ERESs) are ER subdomains where coat protein complex II carriers are assembled for ER-to-Golgi protein transport. In plants, ERES cycles Golgi-associated and Golgi-free states. A plant-specific ER transmembrane protein, MAIGO3, stabilizes Golgi-associated ERESs in Arabidopsis. To identify proteins that interact with MAIGO3, we conducted coimmunoprecipitation coupled to mass spectrometry analysis of GFP-MAIGO3.