SPECIFIC TRITIUM LABELING OF GAMMA-CARBOXYGLUTAMIC ACID IN PROTEINS

A specific method has been devised for the incorporation of tritium (T) into 7-carboxyglutamic acid (Gla) residues in proteins. This is achieved by equilibration of the protein with tritiated 0.05 M deuterium chloride (DC1) in D2G. After removal of the equilibration solvent, the dry protein is heated at 110 °C in vacuo for 3-6 h. The resulting thermal decarboxylation of Gla residues promotes tritium incorporation at the 7 carbon of newly formed glutamic acid residues. More than 99% of the incorporated tritium is in glutamic acid residues after acid hydrolysis. The efficiency of this exchange decarboxylation reaction is 0.95 ±0.14 mol of T incorporated per mol of Gla decarboxylated, compared to the predicted. © 1979, American Chemical Society. All rights reserved.