Comparison of the amino acid sequences of acorn barnacle lectins showing different inhibitory activities toward the crystal growth of calcium carbonate

The amino acid sequence of a D-galactose-binding lectin isolated from the h emolymph of the acorn barnacle Balanus rostratus was determined. The lectin (BRL) (M-r 120K) is a multimeric protein whose subunit consists of 182 ami no acids. The amino acid sequence was compared with those of multiple lecti ns (BRA-2, BRA-3) from Megabalanus rosa to explore the relationship between the structures and the inhibitory activity toward the crystal growth of ca lcium carbonate. Although BRL was 46% identical to BRA-2 and 15% identical to BRA-3, the lectin had no inhibitory activity, unlike BRA-2 and BRA-3. Bo th the number and the localization of acidic amino acid residues and their amide forms were different among them. Observations by scanning electron mi croscopy revealed modifications in the size and morphology of the calcium c arbonate crystals grown in the presence of the lectins.