Characterization of native 40S particles from krebs II mouse ascites tumor cells. I. Phosphorylation in vitro of non ribosomal proteins by a cAMP independent protein kinase

Protein kinases and their protein substrates in free messenger ribonucleoprotein particles and polysomes from mouse plasmacytoma cells

In free messenger ribonucleoprotein particles (mRNP) and polysomes from plasmacytoma cells, a phosphorylated protein/protein kinase system has been characterized by a combination of oligo(dT)-cellulose chromatography and CsCl isopycnic gradient centrifugation. The presence phosphorylated in vivo has been detected in both types of particles. Endogenous protein phosphorylation occurs in vitro by particle-associated cAMP-independent protein kinase(s) using [gamma-32P]ATP and [gamma-32P]GTP. These kinases are sensitive to hemin action. Analysis of mRNP proteins by gel electrophoresis and autoradiography showed strong analogies between the phosphorylation patterns obtained in vivo and in vitro, suggesting a substrate specificity for the associated enzymes. The phosphorylated proteins have been compared to initiation factors and ribosomal proteins. We have partially purified the cAMP-independent protein kinase activities responsible for the endogenous phosphorylation in free mRNP and polysomes; two activities were identified in free mRNP whereas three activities were found to be associated with polysomes.

Characterization of native 40 S particles from Krebs II mouse ascites tumor cells: resolution, nomenclature and molecular weights of the nonribosomal proteins

Native 40 S particles from Krebs II mouse ascites tumor cells were isolated on a large scale. A nonribosomal protein moiety of about 30 proteins could be removed from the ribosomal particles by treatment with 250 mM KCl. These proteins were analysed by two-dimensional polyacrylamide gel electrophoresis and turned out to be mostly acidic in nature. The molecular weights of about 17 proteins were determined by three-dimensional gel electrophoresis. Radioactively labelled nonribosomal protein spots were excised from two-dimensional gel electrophoresis. Radioactively labelled nonribosomal protein spots were excised from two-dimensional gels and transferred directly or after electrodialysis onto the third dimension gel. The proteins fell into a molecular weight range from about 20,000 to 300,000.

Phosphorylation in vivo of non-ribosomal proteins from native 40 S ribosomal particles of Krebs II mouse ascites-tumour cells

Four non-ribosomal proteins from native 40 S ribosomal subunits with mol.wts. of 110 000, 84 000, 68 000 and 26 000 were phosphorylated in vivo when ascites cells were incubated in the presence of [32P]Pi. The 110 000-, 84 000- and 26 000-dalton proteins are identical with phosphorylated products from native 40 S subunits after phosphorylation in vitro by a cyclic nucleotide-independent protein kinase. Phosphoserine was the major phosphorylated amino acid of the proteins phosphorylated in vivo and in vitro.