A Specific Colorimetric Staining Method for γ-Carboxyglutamic Acid-Containing Proteins in Polyacrylamide Gels

In this paper we describe a specific staining method for γ-carboxyglutamic acid (Gla)-containing proteins in polyacrylamide gels. The procedure is based on the colorimetric detection of Gla using 4-diazobenzenesulfonic acid and has the advantage of being simple and fast (1 h). The detection limit is 9.4 pmol for prothrombin and 150 pmol for osteocalcin. It is demonstrated that Gla-proteins can be visualized independent of the presence of an excess of contaminating non-Gla-proteins. The technique may be used for screening of large number of fractions during the purification of Gla-proteins from complex protein mixtures.