Heterogeneous nature of human complement factor B: an electrophoretic approach for the analysis of its oligosaccharide chain structure and its physiological breakdown products

Improvement of BF typing and of BF F subtyping after neuraminidase treatment in the unconverted and converted factor B

When neuraminidase-treated sera are analyzed by agarose gel isoelectric focusing, the factor B (BF) banding pattern is reduced to predominantly one major band without cathodically positioned bands. This not only makes unequivocal typing of BF allotypes possible but also the reliable distinction of all BF F subtype phenotypes with delimitation of "BF F subtype variants". With this new method, serum aging affects the BF determination to a lesser extent than when applying methods that separate native sera. We show that sialylation is not responsible for the BF F subtype polymorphism. All of the investigated BF allotype bands, including those characteristic of the subtypes, show functional hemolytic activity. The banding pattern after removal of neuraminic acid residues ranges from pH 6.8 to 7.3 for factor B, from pH 5.3 to 5.9 for the Ba fragment, and from pH 8.2 to 8.7 for the Bb fragment. The protein structure of factor B is also discussed. Eliminating the superimposition of bands in different BF allotypes, as demonstrated by these methods, proved to be necessary for the detection of hypomorphic BF gene products (BF QL), which are expressed by assumed BF*Q0 alleles in heterozygous genotypes. This allows investigation of BF*Q0 alleles on a protein level, which complements molecular genetic approaches.

Crossed affino-immunoelectrophoresis or affino-blotting with lectins: advantages and limitations for glycoprotein studies

In contrast to the conventional combination of physical, chemical and enzymatic methods used for a structural analysis of glycans in glycoproteins, alternative methods involve affinity electrophoresis as a tool for the detection, characterization, and quantitation of glycoproteins and their carbohydrate moiety, owing to interactions with lectins. Two major approaches involve (i) crossed affino-immunoelectrophoresis and variations thereof, whereby lectin/glycoprotein interactions occur during the electrophoretic runs, or (ii) affino-blotting, where the glycoproteins are electrophoretically separated and then immobilized onto a solid support prior to their interaction with lectins. A critical comparison of these two series of techniques is the scope of the present paper. These techniques are of high interest by virtue of their ability at differentiating a classical glycan structure from unusual oligosaccharide side chains. The former structures will usually be qualitatively and quantitatively described with the easy and fast procedures as well as the simple equipment required for crossed affino-immunoelectrophoresis or affino-blotting, whereas the latter will be good candidates for further structural analyses.