Required for protein transport between the Golgi and the endoplasmic reticulum. May tether coatomer-coated retrograde transport vesicles to the ER membrane through interaction with coatomer as well as the SNARE complex. May contribute to the 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. Binds the coatomer complex through direct interaction with RET2/COPD and RET1/COPA. Binds TIP20 and SEC39/DSL3. Present with 8970 molecules/cell in log phase SD medium.