[Cell Function Research of β-Trefoil Lectins from Mytilidae]

Two novel β-trefoil lectins, MytiLec-1 and SeviL were found from mussels in the coast of Yokohama and Nagasaki. MytiLec-1 was purified from gill and mantle of Mytilus galloprovincialis. It was consisted of 149 amino acid residues and there was no similarity with any other proteins when it was discovered. We advocate for this "Mytilectin" as a new protein family because of their novelty of its primary structure and homologues were also found in other mussels. Glycan array analysis revealed that MytiLec-1 specifically bound to the Gb3 and Gb4 glycan which contained the α-galactoside. MytiLec-1 caused the apoptosis against the Burkitt's lymphoma cells through the interaction of Gb3 express in their cell surface. On the other hand, SeviL obtained from gill and mantle of Mytilisepta virgata showed the specific binding against GM1b, asialo GM1 and SSEA-4 which are known as glycosphingolipid glycan including the β-galactoside. In addition, SeviL was identified as R type lectin by confirmation of QXW motif within its primary structure. Messenger RNA of SeviL like R type lectins was also found among the musssels including Mytilus galloprovincialis. SeviL also showed the apoptosis against asialo GM1 expressing cells. To apply the anticancer lectin as a novel molecular target drug, primary structure of MytiLec-1 was analyzed to enhance the stabilization of confirmation by computational design technique. It was succeeded to produce a monomeric artificial β-trefoil lectin, Mitsuba-1 without losing the Gb3 binding ability. Comparison of biological function between Mitsuba-1 and MytiLec-1 is also described in this study.