Figure 1.

Method for defining the biosynthetic intermediates of pro-αf. Our nomenclature for the pro-αf biosynthetic intermediates is shown to the right, and the method for defining the intermediates is to the left of the structures. Briefly, all forms are recognized by the primary antiserum. The α1,6-linkage-specific serum recognizes all Golgi mannosylated forms, whereas the α1,3-linkage-specific serum only recognizes the terminal α1,3-mannosylated form. EndoM-sensitive (sens.) pro-αf forms carry unbranched α1,6-mannan chains, whereas endoM-resistant (resist.) forms have been branched with α1,2-mannose. Each step is defined genetically by mutants lacking each mannose modification as indicated.