IDENTIFICATION OF ARGININE RESIDUES IN THE SUGAR BINDING SITE OF BRYOHEALIN A LECTIN, FROM THE MARINE GREEN ALGA BRYOPSIS PLUMOSA

Abstract

Bryohealin is lectin isolated from the marine green alga Bryopsis plumosa. It was reported to be involved in the wound-healing process of B. plumosa. The lectin molecule is composed of two identical subunits of 27 kDa each, cross-linked by disulfide bond and showed binding specificity to N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. We demonstrated characterization of a carbohydrate binding site of Bryohealin by chromatography and chemical modification methods. Bryohealin had identical two or more binding sites and shared same binding site for two different carbohydrates (GalNAc and GlcNAc). During chemical modification studies, hemagglutinating activities of Bryohealin were not affected by modification of histidine, tryptophan, aspartic acid, and glutamic acid. When 50% of arginine residues were modified with 1, 2-cyclohexanedione, activity of Bryohealin rapidly decreased. Protection was observed when the arginine modification was performed in the presence of inhibitory sugar (0.15 M GalNAc). The results suggest that the modified arginine is included in the carbohydrate binding site of Bryohealin. Tryptic digested peptides containing modified arginine residues were separated by HPLC. We will indentify which arginine residues are involved in the sugar binding site using mass spectrometry.