EGF DOMAIN SWAP CONVERTS A DROSOPHILA EGF RECEPTOR ACTIVATOR INTO AN INHIBITOR

In Drosophila the function of the epidermal growth factor (EGF) recept or is modulated zygotically by three EGF-like proteins: Spitz (Spi), w hich is a potent activator; Vein (Vn), which is a moderate activator; and Argos (Aos), which is an inhibitor. Chimeric molecules were constr ucted in which the EGE domain of Vn was swapped with the EGF domain fr om each factor. The modified Vn proteins behaved both in vitro and in vivo with properties characteristic of the factor from which the EGF d omain was derived. These results demonstrate that the EGF domain is th e key determinant that gives DER inhibitors and activators their disti nct properties.