This is a lectin that binds sialic acid. Binds 2 calcium ions per subunit. Homopentamer. Pentraxin (or pentaxin) have a discoid arrangement of 5 non-covalently bound subunits. A possible carbohydrate binding site is located between positions 14 and 20. A disulfide bond links Cys-38 to a Cys in the C-terminal half of the chain of 163 residues. Belongs to the pentraxin family.