N-linked oligosaccharides of cobra venom factor contain novel alpha(1-3)galactosylated Le(x) structures

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 oligosacch arides with terminal alpha1-3-linked galactosyl residues, which are antigen ic 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 o ligosaccharides were determined by lectin affinity chromatography, antibody affinity blotting, compositional and methylation analyses, and high-resolu tion H-1-NMR spectroscopy. Approximately 80% of the oligosaccharides are di antennary complex-type, similar to 12% are tri- and tetra-antennary complex -type, and similar to8% are oligomannose type structures. The majority of t he complex-type oligosaccharides terminate in Gal alpha1-3Gal beta1-4(Fuc a lpha1-3)GlcNAc beta1, a unique carbohydrate structural feature abundantly p resent in the glycoproteins of cobra venom.