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 (By similarity). 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 (By similarity).