Trinitrophenylation of equine growth hormone

O. CASCONE; M.J. BISCOGLIO DE JIMÉNEZ BONINO; J.A. SANTOMÉ; A.C. PALADINI

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS

ELSEVIER SCIENCE INC

Año: 1977 vol. 180 p. 303 - 309

0003-9861

The reactivity of the amino groups in equine growth hormone towards trinitrophenylation with picryl sulfonic acid was investigated, and the localization in the molecule of the various kinetically distinguishable amino groups was achieved. The N-terminal residue provides the most reactive amino group followed by the ϵ-amino groups of lysines 179 and 156 and lysines 63, 143, and 165 in decreasing order. Total trinitrophenylation of equine growth hormone brings about a complete loss of the growth-promoting capacity of the protein, but half-maximal potency is still present when there is more than 80% substitution in lysine 179, about 50% in lysine 156, and approximately 20% in each of lysines 63, 143, and 165 besides 100% reaction of the N-terminal group. On the other hand, the immunological properties, as measured in this work, are practically unmodified, even in completely trinitrophenylated equine growth hormone.