Dsl1 is a peripheral membrane protein required for transport between the Golgi and the endoplasmic reticulum. It is localized to the ER membrane, and in vitro it specifically binds to coatomer, the major component of the protein coat of COPI vesicles. Binding sites for coatomer are found on a disorganized region between the C and N termini of Dsl1. The C terminal domain is involved in binding to the Sec39 subunit of the Dsl1p complex. The N terminal complexes with another subunit of the Dsl1p complex called Tip20 which forms heterodimers by pairing the N termini of each protein.