Source:http://linkedlifedata.com/resource/umls/id/C1333412
NCI: Many Epidermal Growth Factor Superfamily Proteins are extracellular signaling molecules (ligands) involved in control of target cell proliferation, cell survival, and cell differentiation. The EGF superfamily is characterized by having at least 6 cysteines residues that form disulphide bonds stacked in a ladder-like arrangement, in the order 1-3, 2-4, 5-6, and which are essential for the stability of the EGF fold. Often arranged as tandem repeats in extracellular proteins, the function of the domains remains unclear, but are thought to perform a structural role.