N-linked oligosaccharides of cobra venom factor contain novel alpha(1-3)galactosylated Le(x) structures
D C Gowda1, J Glushka, Halbeek Hv
1Department of Biochemistry and Molecular Biology, and Vincent T. Lombardi Cancer Center, Georgetown University Medical Center, 3900 Reservoir Road, NW, Washington, DC 20007, USA.
Abstract:
Cobra venom factor (CVF), a nontoxic, complement-activating glycoprotein in cobra venom, is a functional analog of mammalian complement component C3b. The carbohydrate moiety of CVF consists exclusively of N-linked oligosaccharides with terminal alpha1-3-linked galactosyl residues, which are antigenic in human. CVF has potential for several medical applications, including targeted cell killing and complement depletion. Here, we report a detailed structural analysis of the oligosaccharides of CVF. The structures of the oligosaccharides were determined by lectin affinity chromatography, antibody affinity blotting, compositional and methylation analyses, and high-resolution (1)H-NMR spectroscopy. Approximately 80% of the oligosaccharides are diantennary complex-type, approximately 12% are tri- and tetra-antennary complex-type, and approximately 8% are oligomannose type structures. The majority of the complex-type oligosaccharides terminate in Galalpha1-3Galbeta1-4(Fucalpha1-3)GlcNAcbeta1, a unique carbohydrate structural feature abundantly present in the glycoproteins of cobra venom.
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