Purification and partial characterization of a rainbow trout egg lectin

A lectin that agglutinates rabbit red blood cells (RBCs) and human type B RBCs was isolated from ova of rainbow trout Oncorhynchus mykiss . Partial purification of this hemagglutinating material was achieved by affinity chromatography of an H sub(2)O-dialyzed yolk homogenate on rhamnose-linked Sepharose. Polyacrylamide gel electrophoresis (SDS-PAGE) revealed two polypeptides with approximate molecular masses of 19 kilodaltons (kDa) and 30 kDa. Proteins with a molecular mass of less than 20 kDa were separated from other elements of the affinity-purified hemagglutinating material. These proteins were found to lack hemagglutinating activity. When a western blot with rabbit antilectin antiserum was performed against yolk extract, rainbow trout serum, or yolk from larvae, a 30-kDa polypeptide was detected within all three samples. If these lectins are the same molecule, the biological function of the rainbow trout egg lectin may include host defense or perhaps a basic, homeostatic mechanism such as glycoprotein transport.