Role of the histidine residues in the binding mechanism of the growth hormone family

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

COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART B, BIOCHEMISTRY & MOLECULAR BIOLOGY.

ELSEVIER SCIENCE INC

Año: 1990 vol. 95 p. 797 - 802

0305-0491

Reactivity of the hGH histidine residues were studied by reaction with ethoxyformic anhydride. Localization in the molecule of three kinetically distinguishable classes, each including only one residue, was achieved. The first was composed of residue 151, with an apparent velocity constant k = 0.735/min. (similar to that of histidines 19 and 2l in bGH and eGH). The second histidine, 18, with a velocity constant of k = 0.135/min, (similar to that of histidine 169 in the above hormones), and a third, histidine 21, which does not react at all. Neither histidine l5l nor 18 seem to be involved, at least not directly, in bGH binding to specific rat liver sites, since the decrease in this capacity was only 47%, after modification of the former by 77 and 65% after total modification of the latter. These results, and those previously obtained with bGH and eGH, suggest that either histidine 21 is the only indispensable histidine for the binding of growth hormones to specific rat liver sites. or that histidine 21 and/or 18 (19 in bGH and eGH, are located within the growth hormone binding site interaction area.