Open AccessProtein Kinases and Their Protein Substrates in Free Messenger Ribonucleoprotein Particles and Polysomes from Mouse Plasmacytoma Cells
Author(s) -
EGLY JeanMarc,
SCHMITT Michèle,
ELKAIM René,
KEMPF Jules
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06413.x
Subject(s) - polysome , messenger rnp , protein kinase a , biochemistry , ribonucleoprotein , biology , kinase , phosphorylation , small nuclear ribonucleoprotein , protein phosphorylation , microbiology and biotechnology , ribosome , rna , gene
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 of proteins 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 [γ‐ 32 P]ATP and [γ‐ 32 P]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.