Characteristics of the Eukaryotic Initiation Factor 2 Associated 67-kDa Polypeptide

Manas K. Ray, Arup Chakraborty, Bansidhar Datta, Ansuman Chattopadhyay, Debabrata Saha, Avirup Bose, Terry G. Kinzy, Shiyong Wu, Ronald E. Hileman, William C. Merrick, Naba K. Gupta

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

A eukaryotic initiation factor 2 (eIF-2) associated 67-kDa polypeptide (p67) protects the eIF-2 α-subunit from eIF-2 kinase(s) catalyzed phosphorylation, and this promotes protein synthesis in the presence of active eIF-2 kinase(s), [Datta, B., et al. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3324–3328]. This report presents the results of studies related to characteristics of p67 action and the mechanism of p67:eIF-2 interaction: (1) p67 antibodies inhibited protein synthesis in hemin-supplemented rabbit reticulocyte lysates, and such inhibition was reversed by preincubation of the antibodies, specifically with p67. (2) p67 inhibited HRI- and dsI-catalyzed phosphorylations of the eIF-2 α-subunit and histones, but it did not inhibit casein kinase catalyzed phosphorylation of the eIF-2 β-subunit. (3) p67 bound specifically to the eIF-2 γ-subunit. p67 co-immunoprecipitated with the eIF-2 subunits when a p67/eIF-2 mixture was treated with p67 or eIF-2 subunit antibodies and protein A agarose. However, when eIF-2 was preincubated specifically with the eIF-2 γ-subunit antibodies, subsequent co-immunoprecipitation of p67 with the eIF-2 subunits was completely inhibited. Similarly, preincubation of p67 and p67 antibodies prevented subsequent p67 binding to eIF-2. Preincubation of eIF-2, with either eIF-2 α- or β-subunit antibodies, had no effect on p67 co-immunoprecipitation with the eIF-2 subunits. (4) p67:eIF-2 interaction is necessary for p67 activity to protect the eIF-2 α-subunit from eIF-2 kinase(s) catalyzed phosphorylation, p67 bound to eIF-2 only at low Mg2+ concentrations (0.5–2 mM) and protected the eIF-2 α-subunit at these Mg2+ concentrations. High Mg2+ (3–5 mM) completely inhibited p67 binding to eIF-2 and also inhibited p67 activity to protect the eIF-2 α-subunit. These results suggest that p67 binding to eIF-2 is necessary for p67 activity to protect the eIF-2 α-subunit from inhibitory phosphorylation. Several factors, such as the p67 level in the cell, may affect the equilibrium between p67-bound eIF-2 and free eIF-2 and thus regulate protein synthesis.

Original languageEnglish (US)
Pages (from-to)5151-5159
Number of pages9
JournalBiochemistry
Volume32
Issue number19
DOIs
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry

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