Protein-bound phosphorylserine in different tissues and organisms

Abstract

The amount of protein-bound phosphorylserine in different calf tissues, in human and turkey erythrocytes, as well as in several microorganisms, was estimated after acid hydrolysis of the isolated protein fraction. The phosphorylserine was isolated by chromatography on Dowex 50 and Dowex 1, using a small amount of highly 32P-labelled phosphorylserine as a marker. 0.12–0.25 μmole of phosphorylserine (uncorrected for an approximate loss of 75% during acid hydrolysis) per g of wet material was isolated from five different calf tissues and baker's yeast. The corresponding amount from six bacterial strains, as well as human erythrocytes, was less than 0.02 μmole, while 0.09 μmole was obtained from turkey erythrocytes. The results support the view of Langan 7 that phosphoproteins with serine-bound phosphate occur preferentially in eucaryotic cells.