Isolation of vitellin from mature eggs of the palo verde beetle, Derobracus geminatus, was achieved by a combination of gel permeation and anion-exchange chromatography. It is a phosphoglycolipoprotein (Mr ˜250,000) that contains 8% lipids, 4% carbohydrates and 0.2% protein-bound phosphorus. The vitellin is composed of three apoproteins designated I (Mr ˜160,000), II (Mr ˜140,000) and III (Mr ˜50,000). The carbohydrate moiety is composed exclusively of mannose and N-acetylglucosamine. All three apoproteins are glycosylated as shown by flourescein isothiocyanate-conjugated concanavalin A and periodate-Schiff (PAS) staining suggesting the presence of a high mannose structure. Further evidence for the high mannose structure was obtained by the ability of endo-β-N-acetylglucosaminidase H treatment to remove the carbohydrate moieties on the apoproteins.
