RGD Reference Report - Subunit assembly and guanine nucleotide exchange activity of eukaryotic initiation factor-2B expressed in Sf9 cells. - Rat Genome Database

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Subunit assembly and guanine nucleotide exchange activity of eukaryotic initiation factor-2B expressed in Sf9 cells.

Authors: Fabian, JR  Kimball, SR  Heinzinger, NK  Jefferson, LS 
Citation: Fabian JR, etal., J Biol Chem. 1997 May 9;272(19):12359-65.
RGD ID: 1581073
Pubmed: (View Article at PubMed) PMID:9139680

Eukaryotic initiation factor-2B (eIF-2B) is a guanine nucleotide exchange factor (GEF) that plays a key role in the regulation of protein synthesis. In this study, we have used the baculovirus-infected Sf9 insect cell system to express and characterize the five dissimilar subunits of rat eIF-2B. GEF activity was detected in extracts of Sf9 cells expressing the epsilon-subunit alone and was greatly increased when all five subunits were coexpressed. In addition, high GEF activity was observed in extracts containing a four-subunit complex lacking the alpha-subunit. Assembly of an eIF-2B holoprotein was confirmed by coimmunoprecipitation of all five subunits. Gel filtration chromatography revealed that recombinant eIF-2B had the same molecular mass as eIF-2B purified from rat liver and that it did indeed possess GEF activity. Phosphorylation of the substrate eIF-2 inhibited the GEF activity of the five-subunit eIF-2B; this inhibition required the eIF-2B alpha-subunit. The results demonstrate that eIF-2Balpha functions as a regulatory subunit that is not required for GEF activity, but instead mediates the regulation of eIF-2B by substrate phosphorylation. Furthermore, eIF-2Bepsilon is necessary and is perhaps sufficient for GEF activity in vitro.



Gene Ontology Annotations    

Cellular Component

Molecular Function

Objects Annotated

Genes (Rattus norvegicus)
Eif2b1  (eukaryotic translation initiation factor 2B subunit alpha)
Eif2b2  (eukaryotic translation initiation factor 2B subunit beta)
Eif2b3  (eukaryotic translation initiation factor 2B subunit gamma)
Eif2b4  (eukaryotic translation initiation factor 2B subunit delta)
Eif2b5  (eukaryotic translation initiation factor 2B subunit epsilon)


Additional Information