Conserved sequences in the β subunit of archaeal and eukaryal translation initiation factor 2 (eIF2), absent from eIF5, mediate interaction with eIF2γ

Thompson, Glória M.; Pacheco, Eliza; Melo, E. O.; Castilho, Beatriz A.

doi:10.1042/bj3470703

Cited by 33 publications

(35 citation statements)

References 36 publications

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“…The central region, where nb101 and nb131 mutations are located, mediates interactions with eIF2g. The stringency of this interaction is important for the correct selection of the AUG start codon (Thompson et al 2000;Hashimoto et al 2002). This interaction is supported by a crystal structure of P. furiosus aIF2bg in which residues corresponding to the nb101 and nb131 mutations are found in an interface adjacent to the regions that are in close contact with the g-subunit (Sokabe et al 2006).…”

Section: Discussionmentioning

confidence: 55%

Mutations in Caenorhabditis elegans eIF2β Permit Translation Initiation From Non-AUG Start Codons

Zhang

Maduzia

2010

Genetics

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Recognition of the AUG start codon on mRNAs during translation initiation in eukaryotes occurs in a preinitiation complex that includes small ribosomal subunits and multiple translation initiation factors. The complexity of this process and the lack of appropriate tools have prevented its genetic study in multicellular organisms. Here we describe a genetic system in the nematode Caenorhabditis elegans to study how the AUG start codon is selected. We have generated a sensitive reporter assay that allows for the isolation of mutants with reduced fidelity to recognize the AUG start codon. Two mutants were identified to have dominant missense mutations in iftb-1, which encodes the b-subunit of eIF2 (eIF2b). Both mutations occur in a conserved region located outside of the C2-C2 zinc finger domain where yeast SUI3 mutations are localized in Saccharomyces cerevisiae eIF2b. C. elegans iftb-1, as well as mutant eIF2bs carrying the equivalent SUI3 mutations, are able to initiate translation at non-AUG codons that retain two potential base-pairing interactions with the anticodon of the initiator methionyl tRNA. These analyses further support the critical role of eIF2b in start codon selection, and two functional domains within eIF2b are likely involved, one defined by our C. elegans mutants and the other by the yeast SUI3 mutants.

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Section: Discussionmentioning

confidence: 55%

Mutations in Caenorhabditis elegans eIF2β Permit Translation Initiation From Non-AUG Start Codons

Zhang

Maduzia

2010

Genetics

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“…Because the active domain of eIF5 shows homology with the a͞eIF2␤ common region, it was proposed that eIF5 displaces the ␤-subunit during GTPase activation (20). Therefore, taken together with our hypothesis above, the conformational change of Sw1 by the ␤-subunit may lead to recruitment of the eIF5 arginine finger, the proposed catalytic residue of GAP activity, in the vicinity of the ␥-phosphate.…”

Section: Discussionmentioning

confidence: 93%

Structure of archaeal translational initiation factor 2 βγ–GDP reveals significant conformational change of the β-subunit and switch 1 region

Sokabe

Yao

Sakai

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Archaeal͞eukaryotic initiation factor 2 (a͞eIF2) consists of ␣-, ␤-, and ␥-subunits and delivers initiator methionine tRNA (Met-tRNAi) to a small ribosomal subunit in a GTP-dependent manner. The structures of the aIF2␤␥ (archaeal initiation factor 2 ␤␥) heterodimeric complex in the apo and GDP forms were analyzed at 2.8-and 3.4-Å resolution, respectively. The results showed that the N-terminal helix and the central helix-turn-helix domain of the ␤-subunit bind to the G domain of the ␥-subunit but are distant from domains 2 and 3, to which the ␣-subunit and Met-tRNAi bind. This result is consistent with most of the previous analyses of eukaryotic factors, and thus indicates that the binding mode is essentially conserved among a͞eIF2. Comparison with the uncomplexed structure showed significant differences between the two forms of the ␤-subunit, particularly the C-terminal zinc-binding domain, which does not interact with the ␥-subunit and was suggested previously to be involved in GTP hydrolysis. Furthermore, the switch 1 region in the ␥-subunit, which is shown to be responsible for Met-tRNA i binding by mutational analysis, is moved away from the nucleotide through the interaction with highly conserved R87 in the ␤-subunit. These results implicate that conformational change of the ␤-subunit facilitates GTP hydrolysis by inducing the conformational change of the switch 1 region toward the off state.initiator methionine tRNA ͉ ribosome

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“…The loop connecting ␤3 and ␤4 is longer by 17 residues, and it was not completely modeled due to a lack of interpretable electron density. The visible part, residues 48 -50, begins with a turn of 3 10 helix that is stabilized through a hydrogen bond between the carbonyl group of Leu-46 and nitrogen of Glu-49. Serine 51 2 Found on the Web at www.solve.lanl.gov.…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure of the N-terminal Segment of Human Eukaryotic Translation Initiation Factor 2α

Nonato¹,

Widom

Clardy

2002

Journal of Biological Chemistry

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Eukaryotic translation initiation factor 2␣ (eIF2␣) is a member of the eIF2 heterotrimeric complex that binds and delivers Met-tRNA iMet to the 40 S ribosomal subunit in a GTP-dependent manner. Phosphorylation/dephosphorylation of eIF2␣ at Ser-51 is the major regulator of protein synthesis in eukaryotic cells. Here, we report the first structural analysis on eIF2, the three-dimensional structure of a 22-kDa N-terminal portion of human eIF2␣ by x-ray diffraction at 1.9 Å resolution. This structure contains two major domains. The N terminus is a ␤-barrel with five antiparallel ␤-strands in an oligonucleotide binding domain (OB domain) fold. The phosphorylation site (Ser-51) is on the loop connecting ␤3 and ␤4 in the OB domain. A helical domain follows the OB domain, and the first helix has extensive interactions, including a disulfide bridge, to fix its orientation with respect to the OB domain. The two domains meet along a negatively charged groove with highly conserved residues, indicating a likely site for protein-protein interaction. Eukaryotic translation initiation factor 2 (eIF2)1 is a GTPbinding protein that plays a central role in initiating translation. It binds charged initiator tRNA (Met-tRNA i Met ) in a GTPdependent manner to form the ternary complex, eIF2⅐GTP⅐Met-tRNA iMet . This ternary complex binds to the 40 S ribosomal subunit, and additional initiation factors (including eIF3 and eIF1A) join to form the 43 S preinitiation complex and assist in recognizing the start codon (reviewed in Refs. 1-5).Recognition of the translational site is accompanied by eIF5-mediated hydrolysis of eIF2-bound GTP, which releases an eIF2⅐GDP binary complex along with several other initiation factors. For another round of initiation, the GDP in the eIF2 binary complex must be exchanged for GTP in a reaction catalyzed by the multimeric protein factor eIF2B (previously called guanine nucleotide exchange factor) (6). The 40 S⅐mRNA⅐Met-tRNA i Met complex joins the 60 S ribosomal subunit to form an 80 S initiation complex that can enter the elongation phase of protein synthesis.In eukaryotes, eIF2 is a heterotrimer composed of ␣ (36 kDa)-, ␤ (38 kDa)-, and ␥ (52 kDa)-subunits, which appear to remain associated throughout the initiation cycle. Cross-linking and genetic studies have suggested that both ␤-and ␥-subunits are implicated in guanine nucleotide and Met-tRNA i Met binding (7-9). In addition, the ␤-subunit was shown to interact specifically with eIF5 during GTP hydrolysis and also to bind mRNA (10 -12). The ␥-subunit participates in the recognition of the start site for protein synthesis (13).The phosphorylation/dephosphorylation of a conserved serine (Ser-51) in the ␣-subunit is the major regulator of protein synthesis in eukaryotes (reviewed in Ref.2). Phosphorylation of Ser-51 shuts off protein synthesis (14). Three protein kinases, HRI (heme-regulated inhibitor), PKR (RNA-dependent protein kinase), and GCN2, have been identified that specifically phosphorylate Ser-51 in response to a variety of cellular stresses...

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Conserved sequences in the β subunit of archaeal and eukaryal translation initiation factor 2 (eIF2), absent from eIF5, mediate interaction with eIF2γ

Cited by 33 publications

References 36 publications

Mutations in Caenorhabditis elegans eIF2β Permit Translation Initiation From Non-AUG Start Codons

Mutations in Caenorhabditis elegans eIF2β Permit Translation Initiation From Non-AUG Start Codons

Structure of archaeal translational initiation factor 2 βγ–GDP reveals significant conformational change of the β-subunit and switch 1 region

Crystal Structure of the N-terminal Segment of Human Eukaryotic Translation Initiation Factor 2α

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