Epidermal Growth Factor - EGF-family

EGF-family

EGF is the founding member of the EGF-family of proteins. Members of this protein family have highly similar structural and functional characteristics. Besides EGF itself other family members include:

• Heparin-binding EGF-like growth factor (HB-EGF)
• transforming growth factor-α (TGF-α)
• Amphiregulin (AR)
• Epiregulin (EPR)
• Epigen
• Betacellulin (BTC)
• neuregulin-1 (NRG1)
• neuregulin-2 (NRG2)
• neuregulin-3 (NRG3)
• neuregulin-4 (NRG4).

All family members contain one or more repeats of the conserved amino acid sequence:

CX₇CX_4-5CX_10-13CXCX₈GXRC

Where X represents any amino acid.

This sequence contains 6 cysteine residues that form three intramolecular disulfide bonds. Disulfide bond formation generates three structural loops that are essential for high-affinity binding between members of the EGF-family and their cell-surface receptors.