Oxidation of methionine residues in equine growth hormone by Chloramine-T

V. MIHAJLOVICH; O. CASCONE; M.J. BISCOGLIO DE JIMÉNEZ BONINO

INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND CELLULAR BIOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1993 vol. 25 p. 1189 - 1197

1357-2725

Reactivity of methionine residues towards Chloramine-T was studied in the equine growth hormone. With a 20.0 fold molar excess of reactive over methionine, full oxidation of the four residues of the protein is achieved. Methionine 4 is the most reactive group, followed by methionines 72 and 178 - methionine 123 being the less reactive residue. As judged by circular dichroism spectra and binding assays, protein conformation and binding capacity to specific receptors remains unchanged even after full oxidation of all four methionine residues. Results agree with data previously obtained with bovine growth hormone.