Regulates COPI-mediated retrograde protein traffic at the interface between the Golgi apparatus and the endoplasmic reticulum. Involved in the maintenance of the Golgi apparatus morphology. Has no detectable kinase activity in vitro. Homooligomer. Interacts with GORAB. Interacts with COPA, COPB1 and COPB2. Interacts with AP2B1 (By similarity). Localized to the Endoplasmic reticulum-Golgi intermediate and cis-Golgi in an ARF1- independent manner. The protein kinase domain is predicted to be catalytically inactive. Belongs to the protein kinase superfamily.