Plant basic 7 S globulin-like proteins have insulin and insulin-like growth factor binding activity

Basic 7 S globulin (Bg) is a cysteine-rich glycoprotein present in soybean seeds. Mature Bg is composed of high- and low-kDa subunits linked by disulfide bonding. A ligand blotting experiment using [125I]insulin and [125I]insulin-like growth factor-I and -II showed that Bg subunits are able to bind not only to insulin but to insulin-like growth factors-I and -II. Bg-like proteins from other legume species cross-reacted with anti-Bg antibody also bind to insulin and insulin-like growth factors. Bg-like protein in carrot cells was found to have insulin binding activity. Bg-like proteins may be involved in an insulin-like regulatory mechanism in many plant species.