CHARACTERIZATION OF A TRISULFIDE DERIVATIVE OF BIOSYNTHETIC HUMAN GROWTH-HORMONE PRODUCED IN ESCHERICHIA-COLI

A novel protein derivative has been found during process development o f biosynthetic human growth hormone; it has been characterised as huma n growth hormone with a Cys182-Cys189 trisulphide bridge. We have not been able to find a previous report in the literature about this kind of derivative. The characterisation was obtained partly on the full-le ngth derivative and partly on a tryptic fragment of the derivative. Th e full-length derivative was characterised by reduction with 1,4-dithi othreitol followed by electrospray mass spectrometry, treatment with c ysteine and measurement of hydrogen sulphide liberation upon cysteine treatment. The tryptic fragment from peptide mapping was characterised by amino acid analysis, amino acid sequencing and mass spectrometry. All data indicated an extra sulphur atom in the Cys182-Cys189 cystine bridge.