The Amino Acid Substitutions Found in the Genetic Variants of α1-Acid Glycoprotein

• Published in: The Journal of biological chemistry 1971-09, Vol.246 (18), p.5817
• Main Authors: R. Nimberg, T. Motoyama, K. Schmid
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X

α 1 -Acid glycoprotein (orosomucoid), a human plasma globulin, is known to possess two major genetically transmitted variants. In this investigation the specific genetically determined amino acid substitution responsible for the occurrence of these proteins was localized to two heptapeptides by the peptide mapping technique. The variant peptides were subsequently isolated and purified from a peptic digest of the pooled desialyzed glycoprotein by column chromatography, and their sequences were established. It was found that 1 glutamine residue replaces 1 arginine residue, which is consistent with the difference in electrostatic net charge noted between the two aforementioned proteins and represents a single point mutation. The methods of investigation developed in this study will facilitate the identification of the specific amino acid substitutions responsible for the occurrence of the genetic variants of other highly conjugated glycoproteins.