A recombinant polypeptide, composed of the alpha-helical neck region and the carbohydrate recognition domain of conglutinin, self-associates to give a functionally intact homotrimer

Abstract

A recombinant polypeptide composed of the alpha-helical neck region and carbohydrate recognition domain (CRD) of bovine conglutinin was expressed in Escherichia coli. The recombinant protein formed inclusion bodies but could be solubilised using a denaturation-renaturation cycle based on urea and then purified by affinity chromatography on a TSK-N-acetylglucosamide column. The purified product behaved as a homotrimer in non-dissociating conditions, with three CRDs held together by the alpha-helical neck regions. The trimer, although lacking the N-terminal and collagen regions of the native conglutinin, showed the same binding carbohydrate specificities as the native molecule, for the complement fragment C3b and for lipopolysaccharides derived from Gram-negative bacteria.