Sphingolipid Engineering Using Marine Resources

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We report here the purification, characterization, and cDNA cloning of a novel N- acetylgalactosamine-specific lectin from starfish, Asterina pectinifera. The purified lectin showed 19-kDa, 41-kDa and 60-kDa protein bands on SDS-PAGE, possibly corresponding to a monomer, homodimer and homotrimer. The hemagglutination activity of the lectin was specifically inhibited by N-acetylgalactosamine, Tn antigen and blood group A trisaccharide, but not by N-acetylglucosamine, galactose, galactosamine or blood group B trisaccharide. cDNA cloning of the lectin showed that the protein is composed of 168 amino acids including a signal sequence of 18 residues, and possesses the typical C-type lectin motif. These findings indicate that the protein is a C-type lectin.We report here the purification, characterization, molecular cloning, and expression of the gene encoding the enzyme from marine bacterium, Sewanella alga G8. The enzyme was purified by 1,600fold with an overall yield of 24% from a culture supernatant of strain G8. After being stained with a silver staining solution, molecular mass of the purified enzyme was estimated to be 75 kDa on SDS-polyacrylamide gel electrophoresis. The open reading frame of 2,976 nucleotides encoded a polypeptide of 992 amino acids including a signal sequence of 35 residues, 59 residues of which matched the amino acid sequence determined for the purified enzyme. The molecular weight of the mature enzyme was estimated to be 105,994 from the deduced amino acid sequence.