EGF was originally discovered in crude preparations of nerve growth
factor prepared from mouse submaxillary glands as an activity that
induced early eyelid opening, incisor eruption, hair growth inhibition,
and stunting of growth when injected into newborn mice. EGF is
prototypic of a family of growth factors that are derived from
membrane-anchored precursors. All members of this family are
characterized by the presence of at least one EGF structural unit
(defined by the presence of a conserved 6 cysteine motif that forms
three disulfide bonds) in their extracellular domain. EGF is initially
synthesized as a 130 kDa precursor transmembrane protein containing 9
EGF units. The mature soluble EGF sequence corresponds to the EGF unit
located proximal to the transmembrane domain. The membrane EGF precursor
is capable of binding to the EGF receptor and was reported to be
biologically active.
