The leucine-zipper in elongation factor EF-1 delta, a guanine-nucleotide exchange protein, is conserved in Artemia and Xenopus

EEF1D facilitates milk lipid synthesis by regulation of PI3K-Akt signaling in mammals

Mammal's milk is an abundantly foremost source of proteins, lipids, and micronutrients for human nutrition and health. Understanding the molecular mechanisms underlying synthesis of milk components provides practical benefits to improve the milk quality via systematic breeding program in mammals. Through RNAi with EEF1D in primary bovine mammary epithelial cells, we phenotypically observed aberrant formation of cytoplasmic lipid droplets and significantly decreased milk triglyceride level by 37.7%, and exploited the mechanisms by which EEF1D regulated milk lipid synthesis via insulin (PI3K-Akt), AMPK, and PPAR pathways. In the EEF1D CRISPR/Cas9 knockout mice, incompletely developed mammary glands at 9th day postpartum with small or unformed lumens, and significantly decreased triglyceride concentration in milk by 23.4% were observed, as well as the same gene expression alterations in the three pathways. For dairy cattle, we identified a critical regulatory mutation modifying EEF1D transcription activity, which interpreted 7% of the genetic variances of milk lipid yield and percentage. Our findings highlight the significance of EEF1D in mammary gland development and milk lipid synthesis in mammals.

The protein-binding N-terminal domain of human translation elongation factor 1Bβ possesses a dynamic α-helical structural organization

Translation elongation factor 1Bβ (eEF1Bβ) is a metazoan-specific protein involved into the macromolecular eEF1B complex, containing also eEF1Bα and eEF1Bγ subunits. Both eEF1Bα and eEF1Bβ ensure the guanine nucleotide exchange on eEF1A while eEF1Bγ is thought to have a structural role. The structures of the eEF1Bβ catalytic C-terminal domain and neighboring central acidic region are known while the structure of the protein-binding N-terminal domain remains unidentified which prevents clear understanding of architecture of the eEF1B complex. Here we show that the N-terminal domain comprising initial 77 amino acids of eEF1Bβ, eEF1Bβ(1-77), is a monomer in solution with increased hydrodynamic volume. This domain binds eEF1Bγ in equimolar ratio. The CD spectra reveal that the secondary structure of eEF1Bβ(1-77) consists predominantly of α-helices and a portion of disordered region. Very rapid hydrogen/deuterium exchange for all eEF1Bβ(1-77) peptides favors a flexible tertiary organization of eEF1Bβ(1-77). Computational modeling of eEF1Bβ(1-77) suggests several conformation states each composed of three α-helices connected by flexible linkers. Altogether, the data imply that the protein-binding domain of eEF1Bβ shows flexible spatial organization which may be needed for interaction with eEF1Bγ or other protein partners.

Identification of novel isoforms of dairy goat EEF1D and their mRNA expression characterization

Eukaryotic translation elongation factor 1 delta (EEF1D) gene encodes guanine nucleotide exchange protein eEF1Bδ, which participates in the eukaryotic protein synthesis, and plays important roles in regulating cell cycling and milk production. This study firstly focused on detecting the isoforms of dairy goat EEF1D gene and their mRNA expression characterization. Herein, two novel isoforms, EEF1Da and EEF1Dc, were identified in dairy goat. The entire coding sequences of EEF1Da and EEF1Dc isoforms were 843bp and 267bp in length, respectively. Goat EEF1Da had complete conserved domains of elongation factor 1 (EF1) family, and the evolution of goat EEF1Da isoform was agreed with the evolution of species. Expression pattern analysis of different isoforms revealed relatively ubiquitous expression of EEF1D and EEF1Da. While EEF1Dc only expressed in heart, lung, kidney, adipose and muscle. Combining with the analysis results of cloning, qRT-PCR and bioinformatics, EEF1Da is the major alternative splicing form of EEF1D gene. Interestingly, qRT-PCR result showed that the highest expression of EEF1D was in adipose, which is the major component of mammary. This result was consistent with the early research that EEF1D expressed highly in the mammary, which indicated that EEF1D played a potential key role in regulating adipose development and milk production. All these findings would provide a foundation for the further research of EEF1D gene and development of dairy goat industry.

eEF1B: At the dawn of the 21st century

Translational regulation of gene expression in eukaryotes can rapidly and accurately control cell activity in response to stimuli or when rapidly dividing. There is increasing evidence for a key role of the elongation step in this process. Elongation factor-1 (eEF1), which is responsible for aminoacyl-tRNA transfer on the ribosome, is comprised of two entities: a G-protein named eEF1A and a nucleotide exchange factor, eEF1B. The multifunctional nature of eEF1A, as well as its oncogenic potential, is currently the subject of a number of studies. Until recently, less work has been done on eEF1B. This review describes the macromolecular complexity of eEF1B, its multiple phosphorylation sites and numerous cellular partners, which lead us to suggest an essential role for the factor in the control of gene expression, particularly during the cell cycle.

Identification of differentially expressed genes in Con A-activated carp (Cyprinus carpio L.) leucocytes

A cDNA library was constructed from the message RNA (mRNA) obtained from Con A-induced head kidney (HK) leucocytes of carp (Cyprinus carpio L.). Differential screening of the cDNA was carried out by hybridization against the total cDNA probes from normal, Con A-uninduced HK leucocytes or Con A-induced HK leucocytes of carp. The differential expression patterns of certain cDNA clones were confirmed by Southern-blot and Northern-blot analysis. Single-pass of the sequencing analysis and homology search in Genbank (EMBL) revealed those differentially expressed cDNA clones encode for cytochrome c oxidase sub-unit II and III (COII and COIII), elongation factor-1 beta (EF-1 beta), bleomycin hydrolase (BH), heat shock cognate protein 70 (HSC70) and 16S ribosomal RNA (16S rRNA).

Expression of elongation factor 1 beta' in Escherichia coli and its interaction with elongation factor 1 alpha from silk gland

Silk gland elongation factor 1 (EF-1) consists of four subunits: alpha, beta, beta', and gamma. EF-1 beta beta' gamma catalyzes the exchange of GDP for GTP on EF-1 alpha and stimulates the binding of EF-1 alpha-dependent aminoacyl-tRNA to ribosomes. The carboxy-terminal regions of the EF-1 beta subunits from various species are highly conserved. We examined the region of EF-1 beta' that binds to EF-1 alpha by in vitro binding assays, and examined the GDP/GTP exchange activity using deletion mutants of a GST-EF1 beta' fusion protein. We thereby suggested a pivotal amino acid region, residues 189-222, of EF-1 beta' for binding to EF-1 alpha.

A novel variant of translation elongation factor-1beta: isolation and characterization of the rice gene encoding EF-1beta2

A rice gene encoding a novel isoform of translation elongation factor-1beta subunit (termed EF-1beta2) was isolated and characterized. The gene comprises of eight exons, and encodes a 226-amino-acid protein. Expression of EF-1beta2 mRNA is abundant in seeds and cultured cells, but is considerably low in the tissues of the rice seedling. Antiserum raised against an EF-1beta2 synthetic peptide detected a protein with a relative molecular mass of about 32 kDa, indicating the EF-1beta2 gene is actually expressed in rice tissues. EF-1beta2 showed a close similarity to the cognate subunits from plant (beta and beta').

Developmental regulation of elongation factor-1 delta in sea urchin suggests appearance of a mechanism for alternative poly(A) site selection in gastrulae

Elongation factor-1 delta gene expression was analyzed during sea urchin development. EF-1 delta mRNA is present as a single 2.7-kb transcript in unfertilized eggs and in rapidly dividing cleavage stage embryos. It decreases rapidly 6 h after fertilization and then reappears at the gastrula stage as two transcripts of 2.7 and 2.0 kb. cDNA clones encoding the 2.7- and 2.0-kb transcripts were isolated from a sea urchin embryos library. The two cDNAs originate from alternative poly(A) site selection from a unique precursor. Both cDNAs are terminated by a poly(A) tail and were shown to encode for the same protein identified as EF-1 delta. Thus, EF-1 delta gene expression undergoes developmental regulation in early embryos leading to the presence of two poly(A) forms of the transcript. Since the 2.0-kb polyadenylated form of the EF-1 delta transcript appears at gastrula stage, our results suggest that a mechanism for alternative poly(A) site selection of the EF-1 delta transcript appears during embryonic development.

Eukaryotic translation elongation factor 1 alpha: structure, expression, functions, and possible role in aminoacyl-tRNA channeling

This review offers a comprehensive analysis of eukaryotic translation elongation factor 1 (eEF-1 alpha) in comparison with its bacterial counterpart EF-Tu. Altogether, the data presented indicate some variances in the elongation process in prokaryotes and eukaryotes. The differences may be attributed to translational channeling and compartmentalization of protein synthesis in higher eukaryotic cells. The functional importance of the EF-1 multisubunit complex and expression of its subunits under miscellaneous cellular conditions are reviewed. A number of novel functions of EF-1 alpha, which may contribute to the coordinate regulation of multiple cellular processes including growth, division, and transformation, are characterized.

Phosphorylation of elongation factor-1 (EF-1) by cdc2 kinase

Elongation factor-1 (EF-1) is a major substrate for cdc2 kinase in Xenopus oocytes. The guanine-nucleotide exchange factor EF-1 beta gamma delta, appears to have a highly complex macromolecular structure containing several GTP/GDP exchange proteins, valyl-tRNA synthetase, and a putative anchoring protein EF-1 gamma. During meiotic cell division, the factor becomes phosphorylated by cdc2 kinase, not only on EF-1 gamma, but also on two different phospho-acceptors on EF-1 delta. Phosphorylation is concomitant with changes in protein synthesis in vivo. Xenopus oocytes, and potentially all cells, contain a multitude of heteromeric forms of the complex which postulates that EF-1 beta gamma delta is not a "house keeping" factor but a sophisticated regulatory element.

The plant translational apparatus

Protein synthesis in both eukaryotic and prokaryotic cells is a complex process requiring a large number of macromolecules: initiation factors, elongation factors, termination factors, ribosomes, mRNA, amino-acylsynthetases and tRNAs. This review focuses on our current knowledge of protein synthesis in higher plants.

The guanine-nucleotide-exchange complex (EF-1 beta gamma delta) of elongation factor-1 contains two similar leucine-zipper proteins EF-1 delta, p34 encoded by EF-1 delta 1 and p36 encoded by EF-1 delta 2

We have cloned and sequenced a Xenopus cDNA referred to as EF-1 delta 2. The cDNA is homologous to EF-1 delta 1 encoding for EF-1 delta a protein of the guanine-nucleotide exchange complex of elongation factor-1 (EF-1). The protein sequence deduced from the cDNA, contains the two characteristic features of EF-1 delta protein, the leucine-zipper domain and the guanine-nucleotide exchange domain. In vitro and in vivo translation leads to the production of a 36-kDa protein from EF-1 delta and a 34-kDa protein from EF-1 delta 1. The clone EF-1 delta 2 therefore encodes for authentic p36 protein of EF-1 beta gamma delta complex, while EF-1 delta 1 encodes for a newly characterised p34 protein of the leucine zipper family. Both EF-1 delta proteins are simultaneously present in oocytes extracts, at a molecular ratio around 1:10 for p34 versus p36 proteins. Both are associated in a macromolecular structure that is greater than 750 kDa upon gel filtration. The two proteins are targets for Cdc2 kinase in meiotic maturation.

Expression of recombinant elongation factor 1 beta from rabbit in Escherichia coli. Phosphorylation by casein kinase II

The beta subunit of eukaryotic elongation factor 1 (EF-1) catalyzes the GDP/GTP exchange activity on EF-1 alpha. In these studies, two cDNAs for the beta subunit of EF-1 from rabbit are cloned and sequenced. The cDNAs consist of 808 and 798 bp and are identical except for the 5' leader sequences of 67 and 57 bp. Both cDNAs code for a protein of 225 amino acids. Using the pT7-7 expression vector, EF-1 beta was expressed in Escherichia coli and purified to apparent homogeneity by chromatography on DEAE-cellulose and FPLC on Superose 12 and Mono Q. EF-1 beta was highly phosphorylated by casein kinase II, with up to 1.3 mol of phosphate incorporated per mol protein. From microsequence analysis and manual Edman degradation, the majority of the phosphate was shown to be present in serine 106 in the peptide DLFGS106DDEEES112EEA. Serine 112 was also phosphorylated by casein kinase II, but to a lesser extent. Previously, little phosphorylation of the beta subunit by casein kinase II was observed in native EF-1 unless GDP was bound to the alpha subunit (Palen, E., Venema, R.C., Chang, Y-W.E. and Traugh, J.A. (1994) Biochemistry, 8515-8520). In contrast, purified recombinant EF-1 beta was highly and specifically phosphorylated by casein kinase II; GDP and polylysine had little effect on the rate of phosphorylation of the purified subunit.

Characterisation of protein structure/function relationship by sequence analysis without previous alignment: distinction between sub-groups of protein kinases

Using an approach for protein comparison by computer analysis based on signal treatment methods without previous alignment of the sequence, we have analysed the structure/function relationship of related proteins. The aim was to demonstrate that from a few members of related proteins, specific parameters can be obtained and used for the characterisation of newly sequenced proteins obtained by molecular biology techniques. The analysis was performed on protein kinases, which comprise the largest known family of proteins, and therefore allows valid estimations to be made. We show that using only a dozen defined proteins, the specific parameters extracted from their sequences classified the protein kinase family into two sub-groups: the protein serine/threonine kinases (PSKs) and the protein tyrosine kinases (PTKs). The analysis, largely involving computation, appears applicable to large scale data-bank analysis and prediction of protein functions.