FIG. 6.

Proposed structure and processing of WT and ConA 1-1 OSLs. After formation of WT OSL (containing Man₉GlcNAc₂) (A) and ConA 1-1 OSL (containing Man₇GlcNAc₂) (B), glycans are transferred to EP-procyclins. Whereas the WT glycan is efficiently transferred to procyclins, those from mutants are only partially transferred, forming underglycosylated proteins. Subsequently, all the α1-2Man residues are removed from glycans by specific mannosidases, forming procyclins bearing Man₅GlcNAc₂ (WT) or Man₄GlcNAc₂ (ConA 1-1). Whereas WT glycans are not further processed, most glycans in ConA 1-1 EP-procyclins are modified to hybrid types by the addition of an N-acetyllactosamine group to the terminal α1-3Man residue. *, Man residue in WT whose transfer is defective in ConA 1-1. “(+/−)” indicates that some procyclin glycosylation sites are unmodified in ConA 1-1 cells.