Partial purification and characterization of a 60000-dalton phosphoprotein from pig heart tissue

Publisher Website
Google Scholar
Abstract
A 60,000-dalton phosphoprotein (pp60) was purified up to 104-fold by a combination of low-ionic strength extraction, ammonium sulfate fractionation, on-exchange and affinity chromatography, all in detergent-free buffer. Fractionation on .omega.-aminohexylagarose column shows that pp60 actually consists of 2 different polypeptides of similar molecular mass (pp60.omega.1 and pp60.omega.2). Partial hydrolysis with proteases of the proteins 32P-labeled in vitro indicates that pp60.omega.1 and pp60.omega.2 are similar but not identical. Individual phosphoamino acid analysis reveals that pp60.omega.1 is phosphorylated primarily at serine residues while pp60.omega.1 is phosphorylated almost equally at serine and threonine residues. Partial hydrolysis with proteases was also used to explore a possible relationship between the pp60''s and the transforming protein of Rous sarcoma virus (pp60v-src). Apparently, pp60v-src also consists of 2 different polypeptides chemically homologous to the presently purified pp60''s.