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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Molecular properties of the polypeptide chain elongation factors from Thermus thermophilus HB8 have been investigated and compared with those from Escherichia coli. 1. As expected, the factors purified from T. thermophilus were exceedingly heat-stable. Even free EF-Tu not complexed with GDP was stable after heating for 5 min at 60 degrees C. 2. GDP binding activity of T. thermophilus EF-Tu was also stable in various protein denaturants, such as 5.5 M urea, 1.5 M guanidine-HCl, and 4 M LiCl. 3. Amino acid compositions of EF-Tu and EF-G from T. thermophilus were similar to those from E. coli. On the other hand, amino acid composition of T. thermophilus EF-Ts was considerably different from that of E. coli EF-Ts. 4. In contrast to E. coli EF-Tu, T. thermophilus EF-Tu contained no free sulfhydryl group, but one disulfide bond. The disulfide bond was cleaved by sodium borohydride or sodium sulfite under native conditions. The heat stability of the reduced EF-Tu . GDP, as measured by GDP binding activity, did not differ from that of the untreated EF-Tu . GDP. 5. T. thermophilus EF-Ts contained, in addition to one disulfide bond, a sulfhydryl group which could be titrated only after complete denaturation of the protein. 6. Under native conditions one sulfhydryl group of T. thermophilus EF-G was titrated with p-chloromercuribenzoate, while the rate of reaction was very sluggish. The sulfhydryl group appears to be essential for interaction with ribosomes, whereas the ability to form a binary GDP . EF-G complex was not affected by its modification. The protein contained also one disulfide bond. 7. Circular dichroic spectra of EF-Tu from T. thermophilus and E. coli were very similar. Binding of GDP or GTP caused a similar spectral change in both. T. thermophilus and E. coli EF-Tu. On the other hand, the spectra of T. thermophilus EF-G and E. coli EF-G were significantly different, the content of ordered structure being higher in the former as compared to the latter.
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PMID:Studies on polypeptide-chain-elongation factors from an extreme thermophile, Thermus thermophilus HB8. 3. Molecular properties. 3 49

The kinetics of hydrogen-deuterium exhcange in the polypeptide chain elongation factor Tu (EF Tu) from Escherichia coli and that from Thermus thermophilus HB8 has been examined in aqueous solutions at various pH and temperatures by means of infrared absorption measurements. The free EF-Tu from E. Coli has a greater reaction rate at all pH values and at every temperature than that of the GTP-bound or GDP-bound EF-Tu. The free EF-Tu from T. thermophilus, on the other hand, has an alomst equal reaction rate to that of EF-Tu-GDP in the temperature range 38-55 degrees C. For the peptide NH groups belonging to a medium-labile kinetic class, a small but definite difference in the rate of exchange reaction was observed between EF-Tu-GDP and EF-Tu-GTP for both E. coli and T. thermophilus. For less labile peptide NH groups, on the other hand, the rate of the exchange reaction with EF-Tu-GDP from T. thermophilus is only slightly affected by the pH of the solution at 38 degrees C and 45 degrees C, while the rate constant(k) with E. coli EF-Tu-GDP is pH-dependent (log k oc pH). For T. thermophilus EF-Tu, heat stability measurements, kinetics of the rates of GDP and GTP dissociation, and circular dichroic measurements have also been made. The molecular basis for the thermostability of T. thermophilus EF-Tu is discussed.
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PMID:Structural fluctuation of the polypeptide-chain elongation factor Tu. A comparison of factors from Escherichia coli and Thermus thermophilus HB8. 33 41

The amounts of the polypeptide chain elongation factors Tu, Ts, and G, and ribosomal protein SI were assessed under various growth conditions using three independent procedures: (a) Immunoprecipitation and gel electrophoresis, (b) radioimmune assay, and (c) activity measurements. It was demonstrated that, during balanced growth of E. coli, the intracellular levels of these proteins increased in proportion to the growth rate, and the ratio of EF-Tu:EF-Ts:EF-G:protein SI was 4-5:1:1:1, at all growth rates. The effects of isoleucine starvation on the rates of synthesis of these proteins were examined using a pair of isogenic stringent and relaxed strains. The syntheses of all these proteins were found to be under the influence of stringent control. These results indicate that in E. coli the syntheses of the above four proteins are regulated in a coordinated manner and are subject to stringent control.
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PMID:Coordination of levels of elongation factors Tu, Ts, and G, and ribosomal protein SI in Escherichia coli. 34 9

Phage SP RNA-dependent RNA polymerase (SP replicase) was purified from Escherichia coli infected with RNA phage SP. The enzyme was found to be composed of four non-identical polypeptides, i.e. subunits I, II, III, and IV and molecular weights of 74,000, 69,000, 47,000, and 36,000 daltons, respectively. As in the case of phage Qbeta replicase, the largest polypeptide is identical with the ribosomal protein S1, and subunits III and IV with polypeptide chain elongation factors EF-Tu and EF-ts, respectively.. This is based on the behaviour of the subunits on SDS-polyacrylamide gel electrophoresis, isoelectric focusing and immunological cross-reaction. Subunits I, III, and IV of SP replicase are derived from the host cell, while subunit II is coded by phage RNA genome. The striking coincidence of the composition and entity of the structural components of SP replicase with those of Qbeta replicase may indicate the structural and functional requirements of host-derived polypeptides in RNA replicase. The binding activity of S1 (in 70S ribosome comples) to poly (U) is retained in SP replicase complex. In contrast, the GDP binding activity of EF-Tu is masked in SP replicase. It is concluded that S1 is required functionally whereas EF-Tu.EF-Ts are required structurally in RNA replicase.
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PMID:Identification of host-derived subunits of phage SP RNA-dependent RNA polymerase (SP replicase). 36 4

Elongation factor EF-P is a soluble protein that stimulates peptide bond synthesis catalyzed by the 50-S ribosomal subunit. This factor was previously identified and characterized based on its ability to promote the synthesis of formylmethionine-puromycin. In the present work, we tested the ability of EF-P to promote peptide bond synthesis between ribosome-bound fMet-tRNA and several analogues of the 3' terminus of aminoacyl-tRNA, i.e. the cytidylyl(3'-5')-[2'(3')-O-L-aminoacyladenosines]. EF-P promoted synthesis to the greatest extent with certain acceptors which were otherwise inefficient in the peptidyl transferase reaction. This activity of EF-P could not be replaced by the other soluble proteins known to be involved in polypeptide synthesis, such as EF-Tu, EF-Ts and EF-G. One role of EF-P in protein synthesis may be to allow peptide bond synthesis to occur more efficiently with some aminoacyl-tRNAs that are poor acceptors for the ribosomal peptidyl transferase.
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PMID:Peptide bond formation stimulated by protein synthesis factor EF-P depends on the aminoacyl moiety of the acceptor. 38 83

In the preceding papers, we showed that one of the two complementar factors of polypeptide chain elongation factor 1 (EF-1) from pig liver, EF-1alpha, functionally corresponds to bacterial EF-Tu (Nagata, S., Iwasaki, K., and Kaziro, Y. (1976) Arch. Biochem. Biophys. 172, 168), while the other, EF-1betagamma, as well as one of its subunits, EF-1beta, corresponds to bacterial EF-Ts (Motoyoshi, K. and Iwasaki, K. (1977) J. Biochem. 82, 703). Therefore, the interaction between EF-1alpha and EF-1 betagamma or EF-1beta was was examined and the following results were obtained. i) EF-1betagamma catalytically promoted the exchange of [14C]GDP bound to EF-1alpha with exogenous [3H]GDP. ii). In the absence of the exogenous guanine nucleotide, EF-1betagamma as well as EF-1beta could displace GDP bound to EF-1alpha to form an EF-1alpha.EF-1betagamma as well as an EF-1alpha.EF-1beta complex. iii) The occurrence of EF-1alpha.EF-1betagamma and EF-1alpha.EF-1beta complexes was demonstrated by gel filtration on Sephadex G-150. These results strongly indicate that the mechanism of the action of EF-1betagamma or EF-1beta in converting EF-1alpha.GDP into EF-1alpha.GTP is analogous to bacterial EF-Ts, and the reaction is accomplished by the following reactions; EF-1alpha.GDP + EF-1betagamma (or EF-1beta) in equilibrium EF-1alpha.EF-1betagamma (or EF-1beta) + GDP; EF-1alpha.EF-1beta (or EF-1beta) + GTP IN EQUILIBRIUM EF-1alpha.GTP + EF-1betagamma (or EF-1beta).
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PMID:Interaction of subunits of polypeptide chain elongation factor I from pig liver. Formation of EF-1alpha.EF-1betagamma and EF-1beta complexes. 63 30

Polypeptide chain elongation factors have been purified from an extreme thermophile, Thermus thermophilus HB8. By chromatography on a DEAE-Sephadex column, the factors were separated into two peaks; peak I contained a complex of EF-Tu and EF-Ts, while peak II was composed of EF-Tu.gdp and EF-G. These factors were subsequently purified to homogeneous states and crystallized. The EF-Tu . EF-Ts complex could be resolved into EF-Tu and EF-Ts by chromatography on a Sephadex G-200 column in the presence of 8 M guanidine-HCl. The complex could be reconstituted from EF-Tu and the renatured EF-Ts. No immunological cross-reaction was detected between EF-Tu, EF-Ts, and EF-G from T. thermophilus and the antibodies to their corresponding Escherichia coli factors. The molecular weight of EF-Tu . GDP determined by sedimentation equilibrium and sodium dodecylsulfate/polyacrylamide gel electrophoresis was 49000 and 51000 respectively. On the other hand, the molecular weight of EF-Ts was estimated as 27000 and 64000, respectively, by sodium dodecylsulfate/polyacrylamide gel electrophoresis and Sephadex gel filtration, suggesting that the protein existed probably as a dimer. The molecular weight of the EF-Tu . EF-Ts complex determined by sedimentation equilibrium and by gel filtration, was 142000 and 220000, respectively. Since the molar ratio of EF-Tu to EF-Ts in the EF-Tu . EF-Ts complex was one to one, it was suggested that the complex was composed of 2 mol each of EF-Tu and EF-Ts. The molecular weight of EF-G was estimated as 85000, 80000 and 78000 by equilibrium centrifugation, gel filtration, and sodium dodecylsulfate/polyacrylamide gel electrophoresis respectively.
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PMID:Studies on polypeptide-chain-elongation factors from an extreme thermophile, Thermus thermophilus HB8. 1. Purification and some properties of the purified factors. 73 77

Phage Qbeta RNA replicase consists of four nonidentical subunits three of which are required for poly(C)-directed synthesis of poly(G): a phage-coded polypeptide and the two host-supplied protein biosynthesis elongation factors EF-Tu and EF-Ts. After denaturation of the enzyme in 8 M urea, poly(G) polymerase activity can be renaturated by dilution of the denatured subunits into a high ionic strength buffer with glycerol. The renaturation reaction has a broad temperature optimum between 11 and 21 degrees. The extent of renaturation is dependent on enzyme concentration: at low enzyme concentrations and 21 degrees renaturation proceeds for more than 3 h with greater than 40% recovery of activity, whereas at high enzyme concentrations the reaction is complete by 1 h with less than 10% of the poly(G) polymerase activity regained. Activities catalyzed by the elongation factors can be measured while they are part of the replicase complex. Study of rates of renaturation of EF-Tu and EF-Ts dependent activities alone and in the replicase complex revealed that virtually 100% of the EF-Ts activity was recovered more rapidly than could be assayed at temperatures as low as 2 degrees, while the rate of recovery of EF-Tu activity was comparable to that of the poly(G) polymerase activity and was independent of either EF-Tu concentration or the presence of other enzyme subunits. The rate of recovery of the poly(G) polymerase activity was found to be limited by the renaturation of EF-Tu, since the rate was dramatically increased by the addition of undenatured EF-Tu.
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PMID:Renaturation of a multisubunit multiactivity enzyme complex: recovery of phage Qbeta RNA replicase, EF-Tu, and EF-Ts activities after denaturation in urea. 76 66

Bottromycin A2 inhibited MS2 phage RNA-dependent protein synthesis as well as polyuridylic acid-(poly(U))- or polyadenylic acid (poly(A))-dependent polypeptide synthesis. When the ribosomal complex with N-acetyl-[14C]phenylalanyl-tRNA (N-acetyl-[14C]Phe-tRNA) at the A site was subjected to bottromycin A2, the release of N-acetyl-[14C]Phe-tRNA was observed while no release of N-acetyl-[14C]Phe-tRNA from the donor site was observed, indicating that the action of bottromycin A2 is specific to the A site of ribosomes. Due to bottromycin's capacity to release [14C]Phe-tRNA or N-acetyl-[14C]Phe-tRNA from the ribosomal acceptor site (A site), bottromycin A2 inhibited the nonenzymatic binding of N-acetyl-[14C]Phe-tRNA and elongation factor T (EF-T)-dependent binding if the concentration of EF-Tu-GTP-[14C]Phe-tRNA ternary complex was low. Our data are consistent with the possibility that the inhibition of overall polypeptide synthesis by bottromycin A2 is at least partly due to bottromycin A2's activity to release aminoacyl- or oligopeptidyl-tRNA from ribosomes. Among 10 antibiotics tested, bottromycin A2 and lincomycin released aminoacyl-tRNA from ribosomes.
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PMID:Mode of action of bottromycin A2. Release of aminoacyl- or peptidyl-tRNA from ribosomes. 77 Apr 64

Qbeta replicase is a complex of four nonidentical subunits readily dissociable into two subcomplexes: 30 S ribosomal protein S1 and the phage-coded polypeptide (Subunits I + II) and protein synthesis elongation factors EF-Tu and EF-Ts (Subunits III + IV). The affinity of the two subcomplexes for one another increases with increasing ionic strength. The enzyme is capable of initiation of RNA synthesis with synthetic templates only when in the low ionic strength conformation. Elongation of initiated polynucleotide chains is not affectedby ionic strength. Addition of Qbeta RNA to the enzyme also alters its quaternary structure: the EF-Tu-Ts cannot be covalently attached to the other enzyme subunits with bifunctional cross-linking reagents in the presence of RNA. This conformational change is not influenced by ionic strength. The addition of Qbeta RNA to the enzyme, does not result in the release of EF-Tu-Ts from the other enzyme subunits: whereas free EF-Tu-Ts binds GDP independently of salt concentration, this binding by Qbeta replicase is sensitive to high ionic strength and remains so in the presence of Qbeta RNA. Furthermore, RNA does not allow the release of EF-Ts from EF-Tu by GTP as measured by sensitivity of EF-Ts activity to N-ethylmaleimide.
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PMID:Function and structure in phage Qbeta RNA replicase. Association of EF-Tu-Ts with the other enzyme subunits. 77 Apr 71


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