Crystal structure of eIF2B and insights into eIF2–eIF2B interactions

Abstract

Eukaryotic translation initiation factor 2B (eIF2B), a heterodecameric complex of two sets of the a, b, c, d, and e subunits, is the guanine nucleotide exchange factor (GEF) specific for eIF2, a heterotrimeric G protein consisting of the a, b, and c subunits. The eIF2 protein binds GTP on the c subunits and delivers an initiator methionyl-tRNA (Met-tRNA i Met ) to the ribosome. The GEF activity of eIF2B is inhibited by stress-induced phosphorylation of Ser51 in the a subunit of eIF2, which leads to lower amounts of active eIF2 and a limited quantity of Met-tRNA i Met for the ribosome, resulting in global repression of translation. However, the structural mechanism of the GEF activity inhibition remained enigmatic, and therefore the three-dimensional structure of the entire eIF2B molecule had been awaited. Recently, we determined the crystal structure of Schizosaccharomyces pombe eIF2B. In this Structural Snapshot, we present the structural features of eIF2B and the mechanism underlying the GEF activity inhibition by the phosphorylation of eIF2a, elucidated from structurebased in vitro analyses.

Fail-safe control of translation initiation by dissociation of eIF2α phosphorylated ternary complexes

“…K d s showed minimal variations according to nucleotide status 26.6 nM (+GDP) to 32.2 nM (apo-eIF2) (Figure 1C–E). eIF2B has recently been shown to be a dimer (Gordiyenko et al, 2014; Kashiwagi et al, 2016a) and so capable of binding two eIF2 molecules per dimer. Our analyses provided no evidence for co-operative binding and the data fit well to a model where a 5-subunit eIF2B monomer binds one eIF2 heterotrimer (see Materials and methods).…”

Evolutionary engineering improves tolerance for medium-chain alcohols in Saccharomyces cerevisiae

“…Nevertheless, the observation that a mutation in eIF2α, in addition to those in eIF2B, can rescue alcohol-dependent translational inhibition, suggests that alcohols may perturb eIF2/eIF2B activity by binding at the interface of the proteins, and in so doing, alter their interaction. Recently, the crystal structure of the Schizosaccharomyces pombe eIF2B was determined [ 40 ], and studies aimed at experimentally mapping the interaction surfaces between eIF2 and eIF2B were performed [ 40 , 41 ]. The locations of the homologous residues in the S. pombe eIF2Bγ (E81, P156, and C411) corresponding to those found to modulate alcohol sensitivity in the S. cerevisiae eIF2Bγ (D85, P180, C483, respectively) are shown in the S. pombe eIF2B structure in Additional file 1 : Figure S5.…”

“…The locations of the homologous residues in the S. pombe eIF2Bγ (E81, P156, and C411) corresponding to those found to modulate alcohol sensitivity in the S. cerevisiae eIF2Bγ (D85, P180, C483, respectively) are shown in the S. pombe eIF2B structure in Additional file 1 : Figure S5. Also shown in the red hatched box are the location of surfaces of eIF2Bγ and eIF2Bε found to make contacts with eIF2γ, the eIF2 subunit to which GTP is bound [ 40 , 41 ]. E81 and P156 are located in the vicinity of this interaction surface, whereas C411 is further away.…”

The Prodigal Compound: Return of Ribosyl 1,5-Bisphosphate as an Important Player in Metabolism

“…The structure and function of translation initiation factors have been thoroughly reviewed, with descriptions of the functions of the six motifs (98,99).…”