OLIGOSACCHARIDE CONFIGURATION OF FIBRINOGEN KAISERSLAUTERN - ELECTROSPRAY-IONIZATION ANALYSIS OF INTACT GAMMA-CHAINS

Electrospray ionisation mass spectrometry was used to probe the struct ure of the new N-linked oligosaccharide in fibrinogen Kaisers-lautern (gamma 380 Lys-->Asn). The mass increase of 2177 Da in the new gamma c hain indicated the attachment of a fully sialylated biantennary oligos accharide on the new Asn residue; the expected increase for this chang e being 2192 Da. Some 95% of the new oligosaccharide was in the disial ylated state while only 5% of the endogenous gamma chain carbohydrate was disialylated in the control. Mass measurements of intact Kaisersla utem gamma chains after neuraminidase treatment of the native fibrinog en confirmed a total of three residues of sialic acid in the dominant isoform. Incubation with endoglycosidase F showed that the new oligosa ccharide was more resistant to hydrolysis than the endogenous one. Rec ent X-ray analyses of covalently linked D domains show that position g amma 380 is distant from both the GPR binding pocket and the D-D inter face. It appears that the polymerisation defect of this fibrinogen res ults from electrostatic repulsion between condensing protofibrils and that this is induced by the two new residues of sialic acid that are p resent on the new gamma chain.