Cofactors Concanavalin

To immobilize a protein the biologic activity of which depends on a cofactor, this cofactor has to be present in sufficient concentration during the immobilization step. Thus, for example, the lectin Concanavalin A is immobilized in the presence of a buffer containing 0.1 M glucose or a-methylmannoside, 1 mM calcium chloride and 1 mM manganese chloride. 

Several new compounds have been reported that affect the formation of a fibrin clot. Aromatic diamidines, such as, 21, were reported to inhibit several proteolytic enzymes including thrombin.74 Concanavalin A (a globulin protein from the jack bean) inhibits fibrin formation by inhibiting the lipoprotein cofactor in the production of thrombin and thus decreasing the rate of thrombin production.75 Several antibiotics (penicillins and cephalosporins) have been reported to affect fibrin clot formation as well as platelet function. Cephalothin (22) has been shown to delay fibrin polymerization and thus prolong the activated partial thromboplastin time (APTT) and thrombin time tests.78... 

Purified and reduced human Factor VIII exhibits an eight band sub-unit structure (mol. wt. 3.0 X 10 —2.3 x 10 ) as shown by polyacrylamide gel electrophoresis. Rabbit antibody to Factor VIII reacts with all of the sub-units whereas haemophilic antibody reacts with low-molecular-weight sub-units only. Sub-units derived from the largest Factor VIII multimers have a higher binding affinity for D-galactose-specific lectins than have those obtained after reduction of smaller oligomers. Ristocetin cofactor activity of purified Factor VIII is competitively inhibited by two Ricinus communis lectins and by concanavalin A. 

The variety of ligands for AFC includes proteins, cofactors, and any other molecules for which a solute has special affinity. Some common ligands are protein A, antibodies, and concanavalin A. Elution is attained by either a change in pH or ionic strength conditions or the addition of a competitor for the binding. Conditions are as varied as the number of ligands. 

Sinniger, V Tapon-Bretaudie re, J Millieu, C Muller, D Jozefonvicz, J Fischer, A M. Affinity chromatography of sulphated polysaccharides separately fractionated on antithrombin III and heparin cofactor II immobilized on concanavalin A-sepharose. Journal of Chromatography, 1992, 615, 215-223. 

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