42Sp48 in previtellogenic Xenopus oocytes is structurally homologous to EF-1 alpha and may be a stage-specific elongation factor

We have isolated the cDNA for 42Sp48 and EF-1 alpha from mixed stage oocytes and tailbud (stage 22) Xenopus laevis cDNA libraries by use of the cDNA for human elongation factor-1 alpha (EF-1 alpha) as probe. The nucleotide and deduced amino acid sequences of the entire coding region of 42Sp48 and EF-1 alpha cDNA were established. The proposed functional homology of the proteins is reflected in highly conserved amino acid sequences (91% identity), while the large number of silent mutations at the gene level may serve to prevent recombination at their loci. 42Sp48 is apparently encoded by two genes in Xenopus, while no sequences corresponding to 42Sp48 could be found in murine or human genomic DNA. 42Sp48 has been proposed to act as a stage-specific elongation factor in Xenopus. Comparison of the deduced amino acid sequences of 42Sp48 and EF-1 alpha with that of elongation factor Tu from E. coli, for which the three-dimensional structure including that of the GTP binding sites have been determined, supports this hypothesis.     

Elongation factor-1 alpha is a selective regulator of growth factor withdrawal and ER stress-induced apoptosis

To identify genes that contribute to apoptotic resistance, IL-3 dependent hematopoietic cells were transfected with a cDNA expression library and subjected to growth factor withdrawal. Transfected cells were enriched for survivors over two successive rounds of IL-3 withdrawal and reconstitution, resulting in the identification of a full-length elongation factor 1 alpha (EF-1alpha) cDNA. Ectopic EF-1alpha expression conferred protection from growth factor withdrawal and agents that induce endoplasmic reticulum stress, but not from nuclear damage or death receptor signaling. Overexpression of EF-1alpha did not lead to growth factor independent cell proliferation or global alterations in protein levels or rates of synthesis. These findings suggest that overexpression of EF-1alpha results in selective resistance to apoptosis induced by growth factor withdrawal and ER stress.     

Role of yeast elongation factor 3 in the elongation cycle

Investigation of the role of the polypeptide chain elongation factor 3 (EF-3) of yeast indicates that EF-3 participates in the elongation cycle by stimulating the function of EF-1 alpha in binding aminoacyl-tRNA (aa-tRNA) to the ribosome. In the yeast system, the binding of the ternary complex of EF-1 alpha.GTP.aa-tRNA to the ribosome is stoichiometric to the amount of EF-1 alpha. In the presence of EF-3, EF-1 alpha functions catalytically in the above mentioned reaction. The EF-3 effect is manifest in the presence of ATP, GTP, or ITP. A nonhydrolyzable analog of ATP does not replace ATP in this reaction, indicating a role of ATP hydrolysis in EF-3 function. The stimulatory effect of EF-3 is, in many respects, distinct from that of EF-1 beta. Factor 3 does not stimulate the formation of a binary complex between EF-1 alpha and GTP, nor does it stimulate the exchange of EF-1 alpha-bound GDP with free GTP. The formation of a ternary complex between EF-1 alpha.GTP.aa-tRNA is also not affected by EF-3. It appears that the only reaction of the elongation cycle that is stimulated by EF-3 is EF-1 alpha-dependent binding of aa-tRNA to the ribosome. Purified elongation factor 3, isolated from a temperature-sensitive mutant, failed to stimulate this reaction after exposure to a nonpermissive temperature. A heterologous combination of ribosomal subunits from yeast and wheat germ manifest the requirement for EF-3, dependent upon the source of the "40 S" ribosomal subunit. A combination of 40 S subunits from yeast and "60 S" from wheat germ showed the stimulatory effect of EF-3 in polyphenylalanine synthesis (Chakraburtty, K., and Kamath, A. (1988) Int. J. Biochem. 20, 581-590). However, we failed to demonstrate the effect of EF-3 in binding aa-tRNA to such a heterologous combination of the ribosomal subunits.     

Polypeptide chain elongation factor 1 alpha (EF-1 alpha) from yeast: nucleotide sequence of one of the two genes for EF-1 alpha from Saccharomyces cerevisiae.

Messenger RNA for yeast cytosolic polypeptide chain elongation factor 1 alpha (EF-1 alpha) was partially purified from Saccharomyces cerevisiae. Double-stranded complementary DNA (cDNA) was synthesized and cloned in Escherichia coli with pBR327 as a vector. Recombinant plasmid carrying yEF-1 alpha cDNA was identified by cross-hybridization with the E. coli tufB gene and the yeast mitochondrial EF-Tu gene (tufM) under non-stringent conditions. A yeast gene library was then screened with the EF-1 alpha cDNA and several clones containing the chromosomal gene for EF-1 alpha were isolated. Restriction analysis of DNA fragments of these clones as well as the Southern hybridization of yeast genomic DNA with labelled EF-1 alpha cDNA indicated that there are two EF-1 alpha genes in S. cerevisiae. The nucleotide sequence of one of the two EF-1 alpha genes (designated as EF1 alpha A) was established together with its 5'- and 3'-flanking sequences. The sequence contained 1374 nucleotides coding for a protein of 458 amino acids with a calculated mol. wt. of 50 300. The derived amino acid sequence showed homologies of 31% and 32% with yeast mitochondrial EF-Tu and E. coli EF-Tu, respectively.     

Structure and expression of elongation factor 1 alpha in tomato.

A full-length cDNA clone, LeEF-1, has been isolated from tomato for the alpha subunit of elongation factor 1 (EF-1 alpha), a polypeptide which plays a central role in protein synthesis. The 448 amino acid protein encoded by this cDNA appears highly homologous to other EF-1 alpha s having a high degree of similarity (75-78%) to EF1 alpha previously described from both lower eukaryotes and animals. Southern analysis indicated that EF-1 alpha belongs to a small multigene family of 4-8 members in tomato. The pattern of expression of EF-1 alpha mRNA in various tomato tissues was analyzed by Northern analysis, in vitro translation and in situ hybridization. EF-1 alpha mRNA is an abundant species and higher levels of mRNA were found in developing tissues such as young leaves and green fruit compared to the mRNA levels observed in older tissues. The increased levels of EF-1 alpha mRNA therefore appear to correlate with higher levels of protein synthesis in developing tissues.     

Cloning, nucleotide sequence, and expression of one of two genes coding for yeast elongation factor 1 alpha

One gene coding for yeast cytoplasmic elongation factor 1 alpha (EF-1 alpha) was isolated by colony hybridization using a cDNA probe prepared from purified EF-1 alpha mRNA. A recombinant plasmid, pLB1, with a 6-kilobase yeast DNA insert, was found by hybrid selection and translation experiments to carry the entire gene. The nucleotide sequence of the gene with its 5'- and 3'-flanking regions was determined. The 5' and 3' ends of EF-1 alpha mRNA were localized by the S1 nuclease mapping technique. The cloned gene, called TEF1, encodes a protein of 458 amino acids (Mr = 50,071) in a single, uninterrupted reading frame. The amino acid sequence shows a strong homology with several domains of Artemia salina EF-1 alpha cytoplasmic factor, as evidenced by diagonal dot matrix analysis. Protein sequence homology is comparatively much lower with the yeast mitochondrial elongation factor. S1 nuclease mapping of the mRNA, hybridization analysis of chromosomal DNA using intragenic or extragenic DNA probes, and gene disruption experiments demonstrated the existence of two genes coding for the cytoplasmic elongation factor EF-1 alpha/haploid genome. The presence of an intact chromosomal TEF1 gene is not essential for growth of haploid yeast cells.     

Retropseudogenes constitute the major part of the human elongation factor 1 alpha gene family.

The elongation factor 1 alpha (EF-1 alpha) is a protein which promotes the GTP-dependent binding of aminoacyl-tRNA to ribosomes in the protein synthesis process. A human gene coding for EF-1 alpha has previously been cloned and sequenced along with a pseudo-gene. Here, we have further analyzed the family of human EF-1 alpha genes. Using an EF-1 alpha cDNA as probe twelve genomic EF-1 alpha-like clones were isolated and analyzed. Four of these were sequenced and found to contain EF-1 alpha retropseudogenes. A Southern blot analysis indicated that the remaining eight clones also contained retropseudogenes. Genomic Southern blot analysis revealed at least twenty loci in the human genome with sequence homology to the EF-1 alpha cDNA. Besides the already described active gene only one potentially active locus was found. The others appeared to be retropseudogenes. EF-1 alpha retropseudogenes were also found to be abundant in the mammalian species mouse and pig, while the chicken contained only one presumably active EF-1 alpha gene.     

A bacterial clone carrying sequences coding for elongation factor EF-1 alpha from Artemia

A bacterial cDNA clone was identified carrying one third of the nucleotides coding for elongation factor EF-1 alpha from the brine shrimp Artemia. The sequence of codons corresponds with the known sequence of amino acids of EF-1 alpha in the region involved.     

The primary structure of the alpha subunit of human elongation factor 1. Structural aspects of guanine-nucleotide-binding sites

The primary structure of the alpha subunit of elongation factor 1 (EF-1 alpha) from human MOLT 4 cells was determined by cDNA sequencing. The data show that the conservation of the amino acid sequence is more than 80% when compared with yeast and Artemia EF-1 alpha. An inventory of amino acid sequences around the guanine-nucleotide-binding site in elongation factor Tu from Escherichia coli and homologous amino acid sequences in G proteins, initiation and elongation factors and proteins from the RAS family shows two regions containing conserved sequence elements. Region I has the sequence apolar-Xaa-Xaa-Xaa-Gly-Xaa-Xaa-Yaa-Xaa-Gly-LYs-Thr(Ser)- -Xaa-Xaa-Xaa-Xaa-X-apolar. Except for RAS proteins, Yaa is always an acidic amino acid residue. Region II is characterized by the invariant sequence apolar-apolar-Xaa-Xaa-Asn-Lys-Xaa-Asp. In order to facilitate sequence comparison we have used a graphic display, which is based on the hydrophilicity values of individual amino acids in a sequence.     

Molecular cloning,biochemical and structural analysis of elongation factor-1 alpha from Leishmania donovani: comparison with the mammalian homologue

The Src-homology 2 domain containing protein tyrosine phosphatase-1 (SHP-1) is involved in the pathogenesis of infection with Leishmania. Recently, we identified elongation factor-1 alpha (EF-1 alpha) from Leishmania donovani as a SHP-1 binding and activating protein [J. Biol. Chem. 277 (2002) 50190]. To characterize this apparent Leishmania virulence factor further, the cDNA encoding L. donovani EF-1 alpha was cloned and sequenced. Whereas nearly complete sequence conservation was observed amongst EF-1 alpha proteins from trypanosomatids, the deduced amino acid sequence of EF-1 alpha of L. donovani when compared to mammalian EF-1 alpha sequences showed a number of significant changes. Protein structure modeling-based upon the known crystal structure of EF-1 alpha for Saccharomyces cerevisiae-identified a hairpin loop present in mammalian EF-1 alpha and absent from the Leishmania protein which corresponded to a 12 amino acid deletion. Consistent with these structural differences, the sub-cellular distributions of L. donovani EF-1 alpha and host EF-1 alpha were strikingly different. Interestingly, infection of macrophages with L. donovani caused redistribution of host as well as pathogen EF-1 alpha. Since EF-1 alpha is essential for survival, the distinct biochemical and structural properties of Leishmania EF-1 alpha may provide a novel target for drug development.     

Purification and characterization of three elongation factors, EF-1 alpha, EF-1 beta gamma, and EF-2, from wheat germ

Three elongation factors, EF-1 alpha, EF-1 beta gamma and EF-2, have been isolated from wheat germ. EF-1 alpha and EF-2 are single polypeptides with molecular weights of approximately 52,000 and 102,000, respectively. The most highly purified preparations of EF-1 beta gamma contain four polypeptides with molecular weights of approximately 48,000, 46,000 and 36,000, 34,000. EF-1 alpha supports poly(U)-directed binding of Phe-tRNA to wheat germ ribosomes and catalyzes the hydrolysis of GTP in the presence of ribosomes, poly(U), and Phe-tRNA. EF-2 catalyzes the hydrolysis of GTP in the presence of ribosomes alone and is ADP-ribosylated by diphtheria toxin to the extent of 0.95 mol of ADP-ribose/mol of EF-2. EF-1 beta gamma decreases the amount of EF-1 alpha required for polyphenylalanine synthesis about 20-fold. EF-1 beta gamma enhances the ability to EF-1 alpha to support the binding of Phe-tRNA to the ribosomes and enhances the GTPase activity of EF-1 alpha. Wheat germ EF-1 alpha, EF-1 beta gamma, and EF-2 support polyphenylalanine synthesis on rabbit reticulocyte ribosomes as well as on yeast ribosomes.     

Kinetic studies on the role of elongation factors 1 beta and 1 gamma in protein synthesis

An equilibrium isotope exchange technique was used to measure in an Artemia system the catalytic influence of elongation factor (EF) 1 beta gamma on the dissociation of GDP from the complex of elongation factor 1 alpha.[3H] GDP in the presence of an excess of free GDP. The kinetic data demonstrate that, in analogy to procaryotes, dissociation of GDP occurs via the formation of a transient ternary complex of EF-1 alpha.GDP.EF-1 beta gamma. The rate constants for the dissociation of GDP from EF-1 alpha.GDP and from the ternary complex EF-1 alpha.GDP.EF-1 beta gamma were found to be 0.7 x 10(-3) and greater than or equal to 0.7 s-1, respectively. The equilibrium association constants of GDP to EF-1 alpha.EF-1 beta gamma and of EF-1 beta gamma to EF-1 alpha.GDP were found to be 2.3 x 10(5) and 4.2 x 10(5) M-1, respectively. Judged from the known elongation rate in vivo and kinetic constants of nucleotide exchange, it was estimated that the recycling of EF-1 alpha may be a rate-controlling step in eucaryotic translation. As a model for GTP exchange, the formation of the ternary EF-1 alpha.guanylyl (beta gamma-methylene)diphosphonate.EF-1 beta gamma complex was also studied. It was observed that both an increase of the level of aminoacyl-tRNA and of temperature favored the dissociation of this complex, thereby enabling EF-1 beta gamma to recycle as a catalyst. This behavior would explain the frequent occurrence of a heavy form of elongation factor 1 in extracts of the eucaryotic cell.     

The primary structure of elongation factor EF-1 alpha from the brine shrimp Artemia.

cDNA as well as amino acid sequencing has revealed the complete primary structure of elongation factor EF-1 alpha from the brine shrimp Artemia. A comparison with the published sequences of bacterial EF-Tu, mitochondrial EF-Tu and chloroplastic EF-Tu shows that distinct areas of these polypeptide chains are conserved in evolution. The evolutionary distance between prokaryotic and eukaryotic types of EF-Tu is larger than among bacterial and organellar EF- Tus . A number of regions present in both EF-Tu and EF-G from Escherichia coli are also found in EF-1 alpha from Artemia.     

Elongation factor 1 alpha from Saccharomyces cerevisiae. Rapid large-scale purification and molecular characterization

Cytoplasmic elongation factor 1 alpha (EF-1 alpha) was purified to homogeneity from the yeast Saccharomyces cerevisiae using a large-scale procedure. The three steps of purification used were batch adsorption on phosphocellulose, phosphocellulose chromatography and, as the last step, GDP-Sepharose or Biorex column chromatography. The protein is very basic (pI = 9.2) and has an apparent molecular mass of 49 kDa, as determined by polyacrylamide gel electrophoresis using denaturing conditions. It is one of the most abundant proteins in yeast (about 5% of total soluble protein), as shown by two-dimensional gel electrophoresis and by immunological titration. A strong immunological and structural homology was found between yeast EF-1 alpha and elongation factors from other sources. Common immunological features were found between yeast and wheat germ EF-1 alpha. Tryptic hydrolysis of yeast EF-1 alpha in the presence of 25% glycerol generated a large trypsin-resistant polypeptide (Mr = 43,000) which had the same NH2-terminal sequence as the proteolyzed product from rabbit reticulocyte, Artemia salina EF-1 alpha and Escherichia coli EF-Tu. Completed DNA sequence determination of one structural gene for yeast EF-1 alpha confirmed a remarkable conservation of several protein sequence domains in yeast and animal EF-1 alpha (Cottrelle, P., Thiele, D., Price, V., Memet, S., Micouin, J.Y., Marck, C., Buhler, J.M. Sentenac, A., and Fromageot, P. (1985) J. Biol. Chem. 260, 3090-3096).     

Moonlighting functions of polypeptide elongation factor 1: from actin bundling to zinc finger protein R1-associated nuclear localization

Eukaryotic polypeptide elongation factor EF-1 is not only a major translational factor, but also one of the most important multifunctional (moonlighting) proteins. EF-1 consists of four different subunits collectively termed EF-1alphabeta beta'gamma and EF-1alphabeta gammadelta in plants and animals, respectively. EF-1alpha x GTP catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome. EF-1beta beta'gamma (EF-1beta and EF-1beta'), catalyzes GDP/GTP exchange on EF-1alpha x GDP to regenerate EF-1alpha x GTP. EF-1gamma has recently been shown to have glutathione S-transferase activity. EF-2 catalyzes the translocation of peptidyl-tRNA from the A-site to the P-site on the ribosome. Recently, molecular mimicry among tRNA, elongation factors, releasing factor (RF), and ribosome recycling factor (RRF) has been demonstrated and greatly improved our understanding of the mechanism of translation. Moreover, eukaryotic elongation factors have been shown to be concerned or likely to be concerned in various important cellular processes or serious diseases, including translational control, signal transduction, cytoskeletal organization, apoptosis, adult atopic dermatitis, oncogenic transformation, nutrition, and nuclear processes such as RNA synthesis and mitosis. This article aims to overview the recent advances in protein biosynthesis, concentrating on the moonlighting functions of EF-1.     

Interaction of turnip yellow mosaic virus Val-RNA with eukaryotic elongation factor EF-1 [alpha]. Search for a function

The 3'-terminal tRNA-like structure in turnip yellow mosaic virus (TYMV) RNA can be adenylated by tRNA nucleotidyltransferase and subsequently aminoacylated by valyl-tRNA synthetase.Here we present evidence that TYMV Val-RNA can form a stable complex with eukaryotic wheat germ elongation factor EF-1alpha and GTP: the Val-RNA is protected by EF-1alpha.. GTP against digestion by RNase A. By affinity chromatography of TYMV Val-RNA fragments on immobilized EF-1alpha . GTP, it has been established that the valylated aminoacyl RNA domain, which in TYMV RNA is formed by the 3' half of the tRNA-like region, is sufficient for complex formation with EF-1alpha . GTP. The aminoacyl RNA domain is equivalent in tRNAs to the continuous helix formed by the acceptor stem and the T stem and loop. In line with these results, the aminoacyl RNA domain in TYMV Val-RNA complexed to EF-1 alpha . GTP is resistant to digestion by RNase A. It is also shown that the TYMV RNA replicase (RNA-dependent RNA polymerase) isolated from TYMV-infected Chinese cabbage leaves does not contain tRNA nucleotidyltransferase, valyl-tRNA synthetase or EF-1alpha. This suggests that interaction of TYMV RNA with EF-1alpha is not mandatory for replicase activity.