Expression of the carbohydrate recognition domain of bovine conglutinin and demonstration of its binding to iC3b and yeast mannan.

Bovine conglutinin is a collagenous C-type lectin (collectin) that is found in bovine serum. A recombinant protein, composed of the neck-region and the carbohydrate binding domain of bovine conglutinin, has been overexpressed in E. coli. The recombinant protein has been successfully renatured and showed the same sugar binding specificity as the native protein and was able to bind to yeast mannan and complement-activated immune complexes. The binding was calcium-dependent and was inhibited by N-acetylglucosamine. The concentration of N-acetylglucosamine required for 50% inhibition of binding to mannan was 1.77 mM for recombinant conglutinin and 0.71 mM for native conglutinin, respectively. The recombinant conglutinin should be useful in the assay and purification of circulating immune complexes and for therapeutic purposes involving the removal of immune complexes from patient's plasma.