FIGURE 1.

Schematic representation of chimeric glycoprotein substrates. Plasmids encoding GLuc followed by the glycoprotein hormone α subunit (Alpha) or Trf were prepared by ribocloning (8). Locations of Asn glycosylation sites are indicated by the ▴. The location of the sequence PLRSKK that was mutated to PLESEE is indicated for the α subunit. The carboxyl-terminal 19 amino acids from CA6 (CA1–19) were added to the carboxyl terminus of α and the carboxyl terminus of Trf and are indicated by the filled oval. Sequences of CA1–19 and of peptides with partial sequences are shown. All chimeric glycoprotein substrates contained a Myc epitope and His₆ residues. The sequence of the synthetic peptide from the α subunit that contains the key residues required for recognition, α32–46, is also shown.