The EGF family of receptors belongs to the tyrosine kinase receptor (TKR) family 
and plays an important role during embryonic and postnatal development and also 
in the progression of tumors. Her-2/neu/c-erbB-2, a member of the epidermal 
growth factor receptor family, can be cleaved into a soluble extra cellular 
domain (ECD) and a membrane-bound stub fragment. Her-2 ECD from a breast cancer 
cell line SKBR3 was immunopurified and analyzed with matrix-assisted laser 
desorption ionization (MALDI) and carboxyl terminal amino acid sequencing. A 
sequence within the juxtamembrane region (only 11 amino acid residues) PAEQR ASP 
was identified most likely as a primary site of cleavage, PA EQRASP as a minor 
site, that generate the ECD. The sites of cleavage are within the signature 
motif P/GX(5-7)P/G highly conserved in the EGF receptor family.