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

Several possibilities could explain our inability to release Swift and Machamer Golgi Retention Signal retention of the full-length El protein with the mutations we introduced . First, certain mutations in ml might affect assembly of the protein in the membrane because of the proximity of the m2 and m3 domains (we are unable to predict these interactions) . Second, there could be a sequence in addition to ml that is involved in retention of full-length El (perhaps in m2) . Third, retention of El could occur via a different mechanism than retention of Om2,3 and Gml . Replacing the polar residues in ml with a hydrophobic residue containing a smaller side chain than isoleucine might be less disruptive to folding and assembly of El, and allow us to assess the contribution of ml to retention of El . We have recently replaced Gln37 in the full-length El protein with alanine, and this replacement appears to release retention and allow transport to the plasma membrane (unpublished results) . We therefore favor the interpretation that ml is involved in retention of full-length El as well as Am2,3 and Gml. However, more mutations need to be analyzed before concluding that the ml sequence in the full-length El protein is fully responsible for retention .