Epitope mapping of alpha-transforming growth factor: evidence of an immunodominant region

Antisera were produced in rabbits and sheep against both full-length synthetic rat alpha-transforming growth factor and Peptides corresponding to the carboxy-terminal 17 Amino acids. These antisera were used to develop a peptide based radioimmunoassay of alpha-TGF. All antisera reacted only with a restricted region of the alpha-TGF corresponding to the 8 residues (43-50) at the carboxy-terminus: (formula; see text) A series of synthetic Peptides representing deletions or substitutions of Amino acids in this carboxy-terminal region were tested for competition with 125I-alpha-TGF. All changes in the above peptide sequence resulted in a marked reduction in competition. All of the polyclonal antisera demonstrated similar specificity whether they were produced against the 50 amino acid, full-length alpha-TGF, against shorter 17 amino acid and 8 amino acid carboxy-terminal sequences.