LOCUST VITELLOGENIN RECEPTOR - AN ACIDIC GLYCOPROTEIN WITH N-LINKED AND O-LINKED OLIGOSACCHARIDES

1. The locust vitellogenin (VTG) receptor which is embedded in oocyte plasma membranes is a glycoprotein. 2. With various lectins oligosaccharide units have been identified, among them neuraminic acid linked to Gal or GalNAc, mannose chains, Gal linked to GalNAc or GlcNAc and fucose linked to GlcNAc. 3. With specific enzymes it could be shown that mannose and most other oligosaccharides are O-linked while others like fucose are N-linked. 4. Enzymatic removal of all O-linked carbohydrates resulted in a drop of the molecular mass of the receptor protein from 200,000 to 110,000. 5. A total of N- and O-linked oligosaccharides of 54% was calculated. 6. The isoelectric point of the receptor was found to be at pH 3.4 increasing slightly after removal of neuraminic acid. 7. Removal of neuraminic acids destroyed the binding ability for VTG.