Further characterization of eukaryotic initiation factor 5 from rabbit reticulocytes. Immunochemical characterization and phosphorylation by casein kinase II

S. Ghosh, J. Chevesich, U. Maitra

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Abstract

Eukaryotic initiation factor (eIF)-5, isolated from rabbit reticulocyte lysates, is a monomeric protein of M(r) = 58,000-62,000. Immunochemical methods were employed to identify eIF-5 in crude cell lysates. Antisera against purified denatured eIF-5 were prepared in rabbits and characterized by immunoblotting and immunoprecipitation techniques using native and denatured eIF-5 as antigens. Monospecific antibodies to denatured eIF-5 were affinity-purified using eIF-5 blotted onto aminophenylthioether paper. Rabbit reticulocytes, HeLa cells and mouse L cells were lysed directly into a denaturing buffer containing 3% sodium dodecyl sulfate. The denatured proteins were analyzed by polyacrylamide gel electrophoresis followed by immunoblotting with anti-eIF-5 antibodies. With each lysate, one major immunoreactive polypeptide was observed whose molecular weight corresponded to that of purified eIF-5 (M(r) = 58,000-62,000). No degradation products or precursor forms of molecular weight higher than 62,000 were detected in any lysate. These results indicate that isolated eIF-5 is the same size as that found in crude lysates. Additional characterization of eIF-5 indicates that purified eIF-5 can be phosphorylated at serine residues in vitro by casein kinase II. Furthermore, in vitro phosphorylated eIF-5 retains full biological activity in catalyzing the joining of 60 S ribosomal subunits to a preformed 40 S ribosomal initiation complex to form an 80 S initiation complex. Based on its specific activity, we demonstrate that 1 pmol of rabbit reticulocyte eIF-5 mediates the formation of approximately 180 pmol of 80 S initiation complex under the conditions of in vitro initiation reactions.

Original languageEnglish (US)
Pages (from-to)5134-5140
Number of pages7
JournalJournal of Biological Chemistry
Volume264
Issue number9
StatePublished - 1989

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Eukaryotic Initiation Factor-5
Casein Kinase II
Phosphorylation
Reticulocytes
Rabbits
Immunoblotting
Molecular Weight
Molecular weight
Ribosome Subunits

ASJC Scopus subject areas

  • Biochemistry

Cite this

Further characterization of eukaryotic initiation factor 5 from rabbit reticulocytes. Immunochemical characterization and phosphorylation by casein kinase II. / Ghosh, S.; Chevesich, J.; Maitra, U.

In: Journal of Biological Chemistry, Vol. 264, No. 9, 1989, p. 5134-5140.

Research output: Contribution to journalArticle

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