Purification of a phosphoprotein from chromatin of rat liver

Abstract

A simple and effective method to purify a phosphoprotein (B2) (MW 68,000, pI[isoelectric point] 6.2-8) from phenol-soluble non-histone chromatin proteins of rat liver is described. The purification involved only 2 steps, CM-cellulose chromatography and preparative SDS[sodium dodecyl sulfate]/polyacrylamide (10%)-gel electrophoresis. The purified phosphoprotein B2 was shown to be homogeneous by SDS/polyacrylamide-gel electrophoresis. The yield was 2% of total non-histone chromatin proteins. The acidic to basic amino acid ratio of phosphoprotein B2 was less than 1, with high contents of glutamic acid, aspartic acid, arginine, lysine, glycine and alanine. The phosphate content of this protein is 0.3%.