A Golgi retention signal in a membrane-spanning domain of coronavirus E1 protein

How might a sequence buried in the lipid bilayer function in retention? The Lys Asp-Glu-Leu (KDEL) sequence found at the carboxy-terminus of a group of soluble resident ER proteins (HDEL in S. cerevisiae) has been shown to be necessary for their retention in the ER (30, 34) . Recently, putative receptors which recognize these sequences have been identified (24, 42, 48) . It has been suggested that these receptors retrieve escaped ER residents from a pre-Golgi compartment termed the salvage compartment (19, 34) . Ifthe ml sequence is recognized by a receptor, it would have to be a transmembrane receptor whose own membrane-spanning domain recognized ml . As predicted from the structure of the photosynthetic reaction center of Rsp. viridis (5) , polar residues in membrane-spanning domains might be expected to interact with other polar amino acids, and hydrophobic residues with membrane lipids . Although the oligomeric structure of Gml suggests that it could be associated with one or more different proteins, to date we have been unable to detect other proteins by co-immunoprecipitation or cross-linking .