Ethoxyformylation of bovine growth hormone

J.G. FUKUSHIMA; M.J. BISCOGLIO DE JIMÉNEZ BONINO; O. CASCONE; J.A. SANTOMÉ

INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH

Munskgaard

Año: 1983 vol. 21 p. 451 - 457

0367-8377

Reactivity of histidines in bovine growth hormone touwards ethoxyformic anhydride was investigated and localization in the molecule of two kinetically distinguishable classes was achieved, a slow class including only histidine residue l79 (k = 0.180/min) and a fast one composed of histidines 19 and 2l(k = 0.900/min). Total ethoxyformylation of bovine growth hormone brought about a complete loss of its capacity to compete with labelled hormone for rat liver binding sites, but modification of approximately half of the fast histidine group was enough to produce an important decrease in this capacity, circular dichroism studies indicated no significant changes in protein conformation with all three histidine residues modified. Practically full binding-capacity was restored when these residues were regeneraied by treatment with hydroxyiamine. These results suggest that one or both of the fast reacting histidine residues are involved in bovine growth hormone binding to its specific receptors.