Elongation Factor Tu Protein Research Articles

Elongation factor Tu: a molecular switch in protein biosynthesis.

Elongation factor Tu (EF-Tu), the most abundant protein in Escherichia coli, is a guanine nucleotide-binding protein that in the 'on' state acts as a carrier of amino acyl-tRNA to the ribosome. Our knowledge of this essential component of translation has brought substantial progress in the past decade thanks to the co-ordinated application of biochemical, physico-chemical and genetic methods. Crystallographic analysis at 2.6 A resolution and site-directed mutagenesis have revealed structural and functional similarities between the guanine nucleotide-binding domains of EF-Tu and human H-ras p21 protein. The regulation of the expression of the two EF-Tu-encoding genes in E. coli, particularly that of tufB, has been shown to involve diverse mechanisms. Several aspects of the functions of EF-Tu in the elongation cycle have been reinvestigated, leading to new insights. These studies have emphasized the manifold aspects of the mechanisms regulating the activity of EF-Tu in the bacterial cell.

Immunochemical Cross-Reactivities of Protein Synthesis Elongation Factors (EF-Tu and EF-1α Proteins) Support the Phylogenetic Coherence of Archaebacteria

Summary Elongation factor Tu (EF-Tu) proteins have been purified by affinity chromatography on GDP-Sepharose columns, from the eubacterium Thermotoga maritima and from archaebacteria (Sulfolobus solfataricus, Thermoproteus tenax, Thermococcus celer, Pyrococcus wosei, Archaeoglobus fulgidus, Methanococcus thermolitotrophicus, Thermoplasma acidophilum) representative of all known divisions in the arachaebacterial tree except halophiles. Polyclonal antibodies raised against the purified Tu proteins were challenged with homologous and heterologous factors including eukaryotic EF-1α and cross-reactivities were quantified using 125 I labelled Protein A as the reporter molecule. The immunochemical relationships among factors both within and across kingdom boundaries demonstrated that (i) every archaebacterial EF-Tu is closer (immunochemically) to every other archaebacterial EF-Tu than to the analogous proteins of eubacteria and eukaryotes, (ii) within the archaebacteria the immunochemical cross-reactivities grossly correlate with the phylogenetic relatedness of the organisms inferred from similarities in rRNA sequences. The data support the notion that archaebacteria form a phylogenetically coherent taxon.

A mutant of Escherichia coli with an altered elongation factor Tu.

A previously isolated mutant of E. coli K12 HAK 88 [Kuwano, M., Endo, h & yamamoto, M. (1972) J. Bacteriol, 112, 1150-1156], contains a new protein that in two-dimensional gel electropherorgrams has the same molecular weight as normal elongation factor Tu, but whose isoelectric point is altered approximately 0.1 pH unit in the acidic direction. Peptide mapping, purification properties and the ratio of leucyl plus isoleucyl to methionyl plus cysteinyl residues of the normal elongation factor Tu protein and the new protein show a close similarity between the two. The mutation causing the altered electrophoretic mobility is located between argH and rif (79 min on the E. coli genetic map). These biochemical and genetic data indicate that strain HAK 88 has a mutationally altered tufB gene.