Calcium binding activity of marine invertebrate lectins and its role in biomineralization

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1. An enzyme-linked immunosorbent assay for the multiple lectins (BRA-2,BRA-3) of the acorn barnacle Megabalanus rosa was developed. The assay was used to study the multiple lectin levels in the coelomic fluid and various tissue homogenates of M. rosa. The concentrations of the multiple lectins ranged from 0.13 to 2.2mg/ml for BRA-2 and from 0.07 to 0.16 mg/ml for BRA-3, respectively. The protein concentration of the coelomic fluid ranged from 1.4 to 4.8mg/ml. The multiple lectins in the coelomic fluid were also identified as the major proteins by two-dimensional gel electrophoresis.2. The interaction between the multiple lectins and calcium ion was studied by ultraviolet difference spectroscopy. The association constants for BRA-2 and BRA-3 were 1.4X10^4 M^<-1> and 2.2X10^4 M^<-1> at pH8.0, respectively. The multiple lectins inhibited the crystal growth of supersaturated calcium carbonate solution at lectin concentration of 0.1mg/ml. Destruction of the carbohydrate-recognition domains of the lectins decreased the inhibitory activities on the crystal growth. Incorporation of BRAs into the crystal was demonstrated using FITC labeled lectins.