Complete and partial glycophospholipid anchors are found on a fusion protein consisting of luteinizing hormone beta subunit followed by a carboxyl-terminal domain of Thy-1.

The Thy-1 antigen is anchored to the cell surface by a carboxyl-terminal glycophospholipid moiety. To investigate the extent of anchor addition which occurs when such proteins cannot move efficiently to the cell surface, we have expressed a recombinant fusion protein composed of 107 amino-terminal amino acids of bovine luteinizing hormone beta subunit and 46 COOH-terminal amino acids of murine Thy-1 (Thy-1.2 allele). Although the limited amount of fusion protein transported to the cell surface is glycophospholipid-anchored, most of the protein accumulates in an intracellular, endoglycosidase H-sensitive form. The intracellular protein has an unusual structure that contains ethanolamine but does not bind detergent, suggesting either that anchor addition proceeds via a hydrophilic partial intermediate, or that anchor-degradative enzymes exist along the secretory path.