Effect of amidination of lysyl residues on the oxygen affinity of human hemoglobin. Specificity of methyl acetimidate for lysine C5(40)alpha.
Treatment of human oxyhemoglobin with methylacetimidate results in selective amidination of the epfilon-amino group of lysin C5(40)alpha. The modified hemoglobin exhibits increased oxygen affinity, high cooperatively, and normal Bohr effect. Hybrid molecules containing amidinated beta chains and normal alpha chains have normal ligand-binding properties, whereas hybrid molecules containing amidinated alpha chains have ligand-binding properties identical with fully amidinated hemoglobin. Amidination of deoxyhemoglobin produces only minimal changes in ligand-binding properties. We propose that amidination of lysine C5(40)alpha prevents its participation in the salt bond with histidine HC3(146)beta in deoxyhemoglobin, thus shifting the allosteric equilibrium in favor of the high affinity oxy conformation.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D002918:Chymotrypsin; D003488:Cyanogen Bromide; D006454:Hemoglobins; D006801:Humans; D007094:Imides; D007700:Kinetics; D008239:Lysine; D008297:Male; D010100:Oxygen / Q000097:blood*; D010446:Peptide Fragments / Q000032:analysis; D011485:Protein Binding; D014633:Valine
D000596:Amino Acids; D006454:Hemoglobins; D007094:Imides; D010446:Peptide Fragments; D002918:Chymotrypsin; D014633:Valine; D008239:Lysine; D003488:Cyanogen Bromide; D010100:Oxygen