TY - JOUR
T1 - [12-Homoarginine]glucagon
T2 - synthesis and observations on conformation, biological activity, and copper-mediated peptide cleavage
AU - Ross, J. B.Alexander
AU - Rousslang, Kenneth W.
AU - De Haën, Christoph
AU - Lavis, Victor R.
AU - Deranleau, David A.
N1 - Funding Information:
Kemp for typing the manuscript. This work was supported by National Science Foundation Grant GB 18016, and in part by National Institues of Health Grant AM 02456.
PY - 1979/2/26
Y1 - 1979/2/26
N2 - Specific modification of the single lysine residue (Lys-12) in glucagon with O-methylisourea has been effected by blocking the reactivity of the amino terminal histidine with copper, providing a method for obtaining [12-homoarginine]glucagon. It was found that as a side reaction, under the conditions of the modification reaction, Cu(II) catalyzed cleavage of the polypeptide chain between Asp-9 and Tyr-10, and between Lys-12 and Tyr-13. This observation may be of value for development of a sequence-specific peptide cleavage procedure. The dilute solution conformations of glucagon and [12-homoarginine]-glucagon were compared by circular dichroism, fluorescence, phosphorescence, energy transfer, and optical detection of magnetic resonance. The results indicate that conversion of Lys-12 to homoarginine does not alter the helix content, the side chain conformation in the vicinity of the tyrosine and tryptophan residues, or the relative distances and orientations between these residues. However, the modification reduces the hormone potency towards activation of lipolysis in isolated rat epididymal fat cells by a factor of seven. We attribute the loss of potency to an interference with a specific interaction between the lysine residue and the fat cell hormone receptor, and not to a change in the solution conformation of the hormone.
AB - Specific modification of the single lysine residue (Lys-12) in glucagon with O-methylisourea has been effected by blocking the reactivity of the amino terminal histidine with copper, providing a method for obtaining [12-homoarginine]glucagon. It was found that as a side reaction, under the conditions of the modification reaction, Cu(II) catalyzed cleavage of the polypeptide chain between Asp-9 and Tyr-10, and between Lys-12 and Tyr-13. This observation may be of value for development of a sequence-specific peptide cleavage procedure. The dilute solution conformations of glucagon and [12-homoarginine]-glucagon were compared by circular dichroism, fluorescence, phosphorescence, energy transfer, and optical detection of magnetic resonance. The results indicate that conversion of Lys-12 to homoarginine does not alter the helix content, the side chain conformation in the vicinity of the tyrosine and tryptophan residues, or the relative distances and orientations between these residues. However, the modification reduces the hormone potency towards activation of lipolysis in isolated rat epididymal fat cells by a factor of seven. We attribute the loss of potency to an interference with a specific interaction between the lysine residue and the fat cell hormone receptor, and not to a change in the solution conformation of the hormone.
KW - Conformation
KW - Copper-mediated
KW - Glucagon derivative
KW - Peptide cleavage
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U2 - 10.1016/0005-2795(79)90412-4
DO - 10.1016/0005-2795(79)90412-4
M3 - Article
C2 - 427194
AN - SCOPUS:0018801742
SN - 0005-2795
VL - 576
SP - 372
EP - 384
JO - BBA - Protein Structure
JF - BBA - Protein Structure
IS - 2
ER -