Identification of intersubunit domain interactions within eukaryotic initiation factor (eIF) 2B, the nucleotide exchange factor for translation initiation.

ABSTRACT: In eukaryotic translation initiation, eIF2B is the guanine nucleotide exchange factor (GEF) required for reactivation of the G protein eIF2 between rounds of protein synthesis initiation. eIF2B is unusually complex with five subunits (?-?) necessary for GEF activity and its control by phosphorylation of eIF2?. In addition, inherited mutations in eIF2B cause a fatal leukoencephalopathy. Here we describe experiments examining domains of eIF2B? and ? that both share sequence and predicted tertiary structure similarity with a family of phospho-hexose sugar nucleotide pyrophosphorylases. Firstly, using a genetic approach, we find no evidence to support a significant role for a potential nucleotide-binding region within the pyrophosphorylase-like domain (PLD) of eIF2B? for nucleotide exchange. These findings are at odds with one mechanism for nucleotide exchange proposed previously. By using a series of constructs and a co-expression and precipitation strategy, we find that the eIF2B? and -? PLDs and a shared second domain predicted to form a left-handed ? helix are all critical for interprotein interactions between eIF2B subunits necessary for eIF2B complex formation. We have identified extensive interactions between the PLDs and left-handed ? helix domains that form the eIF2B?? subcomplex and propose a model for domain interactions between eIF2B subunits.

SUBMITTER: Reid PJ 

PROVIDER: S-EPMC3318697 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature