[Isolation and general characteristics of lectin from the ascidian Didemnum ternatum]

DTL was isolated from the Didemnum ternatum colonial ascidian and purified by affinity chromatography on cross-linked ovalbumin followed by gel-filtration on Sephadex G-100. SDS-PAGE of the preparation showed a major intense band with a relative mol. wt. of ca. 27 kDa. In the presence of 2-mercaptoethanol, DTL gave rise to a single band of 10 kDa. The lectin isolated was found to agglutinate Ehrlich's carcinoma cells and trypsinized human A, B, O erythrocytes, the hemagglutination being inhibited by GlcNAc, chitobiose, desialylated glycoproteins. Comparison of the sugar moieties of the glycoproteins used as inhibitors led to suggestion that the specific sugar binding site contains, as a dominant sugar, a "bisecting" glucosamine attached through a beta-1,4-linkage to the beta-linked mannose residue of N-glycosidic chains of a complex or hybrid type. An absence of sialic acid residues linked with galactose residues appeared to be necessary for binding DTL with the complex-type sugar chains. DTL inhibits proliferation and reduces DNA biosynthesis ([3H]thymidine incorporation) in tumour cells (HeLa). Principal morphological differences were detected to occur between intact and DTL-treated HeLa cells.