Required for protein transport between the Golgi and the endoplasmic reticulum. May contribute to tethering of coatomer-coated retrograde transport vesicles to the ER membrane through interaction with and stabilization of the SNARE complex. Component of a peripheral membrane protein complex consisting of DSL1, SEC39/DSL3 and TIP20. Bound to a SNARE complex consisting of UFE1, USE1, SEC20 and SEC22 or YKT6 through direct interaction of TIP20 with SEC20. Interacts with DSL1, SEC39/DSL3 and the cytoplasmic domain of SEC20. Present with 6020 molecules/cell in log phase SD medium.