SCG3, also known as secretogranin 3, is a member of the chromogranin/secretogranin family. Members of this family may serve as precursors for biologically active peptides. SCG3 is transported to secretory granules (SGs) in neuroendocrine cells. SCG3 binds strongly to chromogranin A (CgA) in an intragranular milieu and targets CgA to SGs in pituitary and pancreatic endocrine cells. With a sucrose density gradient of rat insulinoma-derived INS-1 cell homogenates, SgIII is localized to the SG fraction and is fractionated to the SG membrane (SGM) despite lacking the transmembrane region.