α Endosulfine Is a Novel Molecule, Structually Related to a Family of Phosphoproteins☆

Abstract We have observed that α endosulfine, the 13KDa form of the endogenous ligand for sulfonylurea receptor recently isolated from porcine brain, displays strong similarities with a phosphoprotein of similar size previously isolated from bovine brain and called ARPP-19. To determine whether the two proteins are different entities, we developed an RT-PCR strategy for analyzing the main portion of bovine α endosulfine. We show that α endosulfine and ARPP-19 are different entities from the same family of proteins, coded by distinct genes.