INHIBITION OF EGF RECEPTOR KINASE-ACTIVIT Y BY HYDROPHOBIC PEPTIDE SECRETED BY A431 1522 CELLS/

A new low molecular weight peptide was found in the conditioned media of A431/1522 cells, which produce recombinant TGF-alpha. This 3 kD pep tide was shown to be highly hydrophobic and capable of permeabilising plasma membranes of A431 cells. As it follows from the data of I-125 E GF-radioreceptor analysis and P-32-autophosphorylation assay the pepti de doss fist serve as a ligand of the EGF receptor but strongly inhibi ts the EGF receptor kinase activity at the micromolar range.