Covalent glycophospholipid binding to hemoglobin. A new post-translational modification occurring in erythrocytes exposed to insulin

Abstract

In this work a novel hitherto unrecognised hemoglobin (Hb) fraction, HbA1x, which we detected previously in hemolysates of erythrocytes exposed to high concentration of insulin under hypoglycemic conditions, both in vivo and in vitro, was analysed. Both β chains of Hb in HbA1x were found to be modified by covalent binding of a substance containing sugar, phosphate and fatty acid residues. HbA1x was therefore termed glycophospholipid (GPL) adduct (Hb-GPL). To our knowledge, this is the first demonstration of such modification of Hb, as well as the first demonstration of post-translational GPL binding to proteins in response to insulin binding to a cell. The mechanism proposed for Hb-GPL formation is briefly described.