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

In addition to the VSV G protein, the ml sequence was also able to retain another plasma membrane protein called am. The am protein consists ofthe alpha subunit of human chorionic gonadotropin fused to the membrane-spanning domain and cytoplasmic tail ofVSV G (16) , and appears to be transported to the cell surface as a monomer (17) . In this case, we were able to replace the single membrane-spanning domain of am with either ml or the third membrane-spanning domain (m3) from the El protein using restriction sites in the coding sequence. These chimeric proteins are termed am1G and am3G, respectively. Whereas am3G was transported to the plasma membrane like the parent molecule, am1G was retained in the Golgi region of transfected COS cells (Fig. 4) . The two N-linked oligosaccharides on am1G remained endo H sensitive, whereas those on am and am3G were processed to an endo H-resistant form (data not shown) .