Isolation and partial characterization of a L-rhamnose-binding lectin from the globiferous pedicellariae of the toxopneustid sea urchin, Toxopneustes pileolus

A novel lectin from the large globiferous pedicellariae of the toxopneustid sea urchin, Toxopneustes pileolus, was isolated by a combination of gel permeation chromatography and affinity chromatography techniques. On an SDS-PAGE gel, single bands were detected with relative molecular weights of 28 and 170 kDa in the presence and absence of 2-mercaptoethanol, respectively, suggesting that this lectin is present as a homohexamer. The 170-kDa lectin was named sea urchin lectin-III (SUL-III). The N-terminal partial amino acid sequence of the intact 28-kDa subunit of SUL-III was determined as follows: RCPQPAALPYRIAQIGNRFL. Agglutination of rabbit erythrocytes by SUL-III was most effectively inhibited by L-rhamnose. SUL-III induced mitogenic stimulation on murine splenocytes. These results suggest that SUL-III may be a novel L-rhamnose-binding lectin with potent bioactivity.