Fig. 1.

Protein N-glycosylation pathways in insect and mammalian cells. Monosaccharides are indicated by their standard symbolic representations, as defined in the key. The insect and mammalian N-glycan processing pathways share a common intermediate, as shown. The major products derived from this intermediate are paucimannose and complex N-glycans in insect and mammalian cells, respectively. It is generally recognized that insect cells have only a limited capacity, at best, to produce complex N-glycans. However, this model accommodates the possibility that some insect cells can produce complex N-glycans under certain circumstances. Complex N-glycans are extremely diverse and only representative examples are shown in the figure. The structures of the N-glycans produced by transgenic lepidopteran insect cell lines, modified baculovirus expression vectors (BEVS), and BEVS-transgenic insect cell combinations are shown as well.