Expression and characterization of a carbohydrate-binding fragment of rat aggrecan.

The COOH-terminal portion of cartilage proteoglycan core protein, aggrecan, expressed by in vitro translation, binds carbohydrate-containing affinity columns. The in vitro expression approach has been used to define the sugar-binding portion of the core protein. The active fragment, which corresponds closely to the carbohydrate-recognition domains in the family of Ca(2+)-dependent (C-type) animal lectins, has been expressed in bacteria and characterized. The CD spectrum of the domain is very similar to the spectrum of the binding domain of serum mannose-binding protein, suggesting that its overall structure probably resembles the known three-dimensional structure of the mannose-binding domain. The binding specificity of the core protein fragment has been characterized using a solid-phase assay. The results suggest that the monosaccharide-binding site is also similar to that in other C-type carbohydrate-recognition domains.