Determination of the disulfide bond pairings in bovine transforming growth factor-alpha.

A rapid method for determining the three disulfide bond pairings in bovine transforming growth factor-alpha (bTGF-alpha) was developed by digesting bTGF-alpha with thermolysin followed by separation of the generated peptides by reversed-phase HPLC. The disulfide-bonded peptides were identified by amino acid sequencing and fast atom bombardment mass spectrometry. The disulfide bond pairings in bTGF-alpha were determined to be homologous to those in the human and mouse TGF-alpha molecules. A species of low bioactivity isolated from the folding/oxidation mixture of chemically synthesized bTGF-alpha was demonstrated to contain two incorrect disulfide bonds. These results indicate that mispairing of disulfide bonds in bTGF-alpha significantly reduces the activity of this molecule.