STRUCTURE & FUNCTION OF SNAKE VENOM GLYCOPROTEINS

点击翻译按钮获取中文摘要

RVV-X (93 kDa) and RVV-V (31 kDa), the coagulation factor X and V activating glycoproteins of Russell's Viper venom, are synthesized by the same venom gland and are capable of activating blood coagulation factors X and V, respectively. They both contain N-linked oligosaccharides but are differentially glycosylated. Cobra venom mucin is a high molecular weight, heavily glycosylated protein that is secreted abundantly by the cobra venom gland. It contains largely 0-linked oligosaccharides with terminal cc-galactosylated Le' and Le' antigenic determinants. Recent studies suggest that this mucin activates human complement in an cc-galactoside residue-dependent manner The carbohydrates released from RVV-X., RVV-V and cobra mucin were analyzed by a combination of electrospray mass spectrometry, collision-induced decomposition (CID), and for cobra mucin, specific enzymatic hydrolysis. The objective was to provide broad mass profiles and general structural features for the N-linked glycans while more specific structural details for the cobra mucin oligomers were sought, related to the presence of theantigenic (x-galactose residues. Base-released oligosaccharide alditols from cobra mucins were partitioned on Bio-Gel P 30 columns and then digested with coffee bean (x-galactosidase. By comparing the mass profiles for the smaller oligomers before and after enzyme treatment, combined with CID structural analysis, it was shown that (x-galactosidase sensitivity required the presence of a terminal hexose-hexose pair. The combination of endo-o-galactosidase and CID wasused to probe for internal structural features such as branching and tandem hexose repeats. Molecular weight distributions of the intact species of the very large oligomers are being determined by M[ALDI-TOF MS.