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Legate KR, Andrews DW. The beta-subunit of the signal recognition particle receptor is a novel GTP-binding protein without intrinsic GTPase activity. J Biol Chem 2003; 278:27712-20. [PMID: 12759365 DOI: 10.1074/jbc.m302158200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The beta-subunit of the signal recognition particle receptor (SRbeta), a member of the Ras family of small molecular weight GTPases, is involved in the targeting of nascent polypeptide chains to the protein translocation machinery in the endoplasmic reticulum membrane. We purified SRbeta from an expressing strain of Escherichia coli and investigated the properties of the isolated GTPase. We find that, unlike other Ras family GTPases, most SRbeta purifies bound to GTP, and SRbeta-bound GTP is not easily exchanged with solution GTP. SRbeta possesses no detectable GTPase activity. Although a stable interaction between SRbeta and ribosomes is observed, SRbeta is not stimulated to hydrolyze GTP when incubated with ribosomes or ribosome-nascent chains. A GTPase mutant harboring a mutation in a region predicted to be functionally important, based on observations made in related GTPases, binds GTP with faster kinetics and appears to be a less stable protein but otherwise displays similar properties to the wild-type SRbeta GTPase. Our results demonstrate that as an isolated GTPase, SRbeta functions differently from the Arf- and Ras-type GTPases that it is most closely related to by sequence.
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MESH Headings
- Animals
- Chromatography, High Pressure Liquid
- Cross-Linking Reagents/pharmacology
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Endoplasmic Reticulum/metabolism
- Escherichia coli/metabolism
- GTP Phosphohydrolases/metabolism
- GTP-Binding Proteins/metabolism
- Guanosine Triphosphate/metabolism
- Humans
- Hydrolysis
- Intracellular Membranes/metabolism
- Kinetics
- Mutagenesis, Site-Directed
- Mutation
- Plasmids/metabolism
- Precipitin Tests
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/physiology
- Receptors, Peptide/chemistry
- Receptors, Peptide/physiology
- Ribosomes/metabolism
- Saccharomyces cerevisiae/metabolism
- Spectrometry, Fluorescence
- Time Factors
- Ultraviolet Rays
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Affiliation(s)
- Kyle R Legate
- Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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2
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Nozal MJ, Bernal JL, Toribio L, Marinero P, Moral O, Manzanas L, Rodriguez E. Determination of glutathione, cysteine and N-acetylcysteine in rabbit eye tissues using high-performance liquid chromatography and post-column derivatization with 5,5'-dithiobis(2-nitrobenzoic acid). J Chromatogr A 1997; 778:347-53. [PMID: 9299745 DOI: 10.1016/s0021-9673(97)00473-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A high-performance liquid chromatographic method to determine glutathione, cysteine and N-acetylcysteine in rabbit retina, vitreous and lens has been developed. The thiols are separated using a 25 x 0.46-cm octadecylsilane column with 0.5 M phosphate buffer, pH 3, as mobile phase. The detection, at 412 nm, involves a post-column derivatization with 5,5-dithiobis(2-nitrobenzoic acid) in presence of cationic micelles of hexadecyltrimethylammonium bromide that enhances the sensitivity. The detection limits are 0.21, 0.92 and 0.61 mumol/g wet sample for glutathione, cysteine and N-acetylcysteine, respectively.
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Affiliation(s)
- M J Nozal
- Department of Analytical Chemistry, Faculty of Sciences, University of Valladolid, Spain
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3
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Nagel K, Voigt J. Regulation of the uncoupled GTPase activity of elongation factor G (EF-G) by the conformations of the ribosomal subunits. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1174:153-61. [PMID: 8357832 DOI: 10.1016/0167-4781(93)90109-q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The elongation factor G (EF-G) GTPase activity is induced by either 70S ribosomes or 50S ribosomal subunits. The GTPase activity induced by 50S ribosomal subunits is predominant at low concentrations of monovalent cations and decreases with increasing concentrations of K+ or NH4+. Double-logarithmic plots of the data reveal straight lines with different slopes for low and high concentrations of monovalent cations, respectively, intersecting at the same concentration of monovalent cations where maximal EF-G GTPase activity is measured in the presence of both ribosomal subunits. Substantially the same curves are obtained when 50S ribosomal subunits are substituted by 50S CsCl-core particles partially reconstituted by addition of purified 50S split proteins L7/L12. Intact 30S ribosomal subunits, but not 30S CsCl-core particles are able to associate with 50S ribosomal subunits and to modulate ribosome-dependent EF-G GTPase activity. Therefore, our data clearly show that the biphasic courses of the NH4+ and K+ curves of EF-G GTPase activity induced by 50S ribosomal subunits are not due to contaminations with 30S ribosomal subunits but result from different conformations of EF-G/50S ribosomal-subunit complexes at low and high concentrations of monovalent cations, respectively. CD spectra of 50S ribosomal subunits measured under different salt conditions have shown that the conformation of the 50S ribosomal subunits is strongly dependent on the concentration of monovalent cations. The conformation of 30S ribosomal subunits is, however, considerably stronger influenced by the Mg2+ than by the concentration of monovalent cations. The salt effects on the conformation of the 30S ribosomal subunits correspond to the salt effects on the association of ribosomal subunits and the modulation of EF-G GTPase activity by 30S ribosomal subunits. Since, in the presence of both ribosomal subunits, EF-G GTPase activity is maximal at the same concentration of monovalent cations where obviously a spontaneous conformation change of 50S ribosomal subunits takes place, we postulate that EF-G GTPase primarily acts on the ribosomes by changing the conformation of 50S ribosomal subunits. The resulting model is based on the assumption that EF-G GTPase activity is considerably more strongly induced by the 'substrate conformation' ('state I') than by the 'product conformation' of the 50S ribosomal subunits ('state II'). A spontaneous transformation of 'state II' to 'state I' is expected to occur in the absence of mRNA, aminoacyl-tRNA and EF-T especially under salt conditions favouring state I.
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Affiliation(s)
- K Nagel
- Botanisches Institut, Technischen Universität Braunschweig, Germany
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4
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Hattori S, Yamashita T, Copeland TD, Oroszlan S, Shih TY. Reactivity of a sulfhydryl group of the ras oncogene product p21 modulated by GTP binding. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)66910-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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5
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De Vendittis E, Masullo M, Bocchini V. The elongation factor G carries a catalytic site for GTP hydrolysis, which is revealed by using 2-propanol in the absence of ribosomes. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)38520-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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6
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Eberly SL, Spremulli LL. Purification and characterization of the mitochondrial translocase from Euglena gracilis. Arch Biochem Biophys 1985; 243:246-53. [PMID: 3933427 DOI: 10.1016/0003-9861(85)90793-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Euglena gracilis mitochondrial protein biosynthetic elongation factor G (EF-Gmt) has been purified in four steps to greater than 50% homogeneity by use of a fusidic acid affinity procedure and conventional chromatographic techniques. The purification scheme results in 1100-fold purification with about 3% recovery of the total EF-G activity present in the postribosomal supernatant prepared from whole cell extracts. E. gracilis EF-Gmt has an approximate molecular weight of 76,000, comparable to that observed for procaryotic translocases. As is the case for other translocases which have been examined, pretreatment of E. gracilis EF-Gmt with N-ethylmaleimide results in a loss of polymerization activity, indicating a role for an essential cysteine residue in catalytic activity. GDP partially protects EF-Gmt from N-ethylmaleimide inactivation. E. gracilis EF-Gmt functions well on both Escherichia coli and E. gracilis chloroplast ribosomes, but has negligible activity on wheat germ cytoplasmic ribosomes. In this respect, it differs significantly from the mitochondrial translocase of yeast which has very little activity on chloroplast ribosomes. When assayed on E. coli ribosomes, E. gracilis EF-Gmt is sensitive to the steroid antibiotic, fusidic acid, at levels similar to that required for inactivation of E. coli EF-G. It is less sensitive than E. gracilis chloroplast EF-G, and is more sensitive than Bacillus subtilis EF-G. When assayed on E. gracilis chloroplast ribosomes, the same trends in sensitivities are observed, although the exact level of fusidic acid required for inactivation is slightly altered.
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7
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Chinali G, Parmeggiani A. Differential modulation of the elongation-factor-G GTPase activity by tRNA bound to the ribosomal A-site or P-site. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 125:415-21. [PMID: 6180894 DOI: 10.1111/j.1432-1033.1982.tb06699.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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8
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9
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Girshovich AS, Bochkareva ES, Ovchinnikov YA. Elongation factor G and protein S12 are the nearest neighbours in the Escherichia coli ribosome. J Mol Biol 1981; 151:229-43. [PMID: 7040673 DOI: 10.1016/0022-2836(81)90513-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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10
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Kashparov IA, Semisotnov GV, Alakhov YB. Interaction of the N-terminal and C-terminal domains of elongation factor G on formation of complexes with guanyl nucleotides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 118:417-21. [PMID: 7285933 DOI: 10.1111/j.1432-1033.1981.tb06418.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Polarized fluorescence studies of interaction between guanyl nucleotides (GTP and GDP) and elongation factor G and its N-terminal tryptic fragment T*/s, carrying a fluorescent group (aminorhodamine B) at the exposed cysteine residue, has shown that binding on nucleotides by an intact EF-G molecule at neutral pH essentially affects the mobility of the fluorescent group. GTP binding changes its relaxation properties to a greater extent than GDP binding. At the same time it was demonstrated that the spectrum of relaxation time of the fluorescent group practically does not change on binding of nucleotides by the N-terminal fragment T*/2 (in the absence of the C-terminal domain) or in the case when the three-dimensional structure of the intact EF-G molecule is destabilized (pH 10). Comparison of the relaxation properties of EF-G and its N-terminal fragment T*/2, carrying a fluorescent group at the exposed cysteine residue, at pH 7.5 and 10, indicates that the C-terminal domain is involved in the formation of the close environment of the exposed cysteine residue located in the N-terminal part of EF-G. A conclusion is drawn on the nucleotide-induced influence of the C-terminal domain on a change of the exposed cysteine residue environment on guanyl nucleotide binding with EF-G at neutral pH and a hypothetical model of the EF-G molecule is proposed.
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11
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Maassen JA, Möller W. Photochemical cross-linking of elongation factor G to 70-S ribosomes from Escherichia coli by 4-(6-formyl-3-azidophenoxy)butyrimidate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 115:279-85. [PMID: 7016534 DOI: 10.1111/j.1432-1033.1981.tb05235.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Ribosomal proteins situated at or near the binding site of elongation factor G (EF-G) on the Escherichia coli ribosome have been identified by use of the heterobifunctional cross-linker 4-(6-formyl-3-azidophenoxy)butyrimidate. Four different preparations of EF-G, in which the number of cross-linker molecules coupled to EF-G ranged from four to seven, all cross-linked to 50-S subunit proteins L1, L3 and L11 as well as to 30-S subunit proteins S3 and S4. Cross-linking of EF-G to ribosomal proteins was tested electrophoretically. In the case of L7/L12 and L11 immunological methods were also used. Cross-linking of EF-G to L1, L3, L11, S3 and S4 is specific as judged from the fact that addition of unmodified EF-G and of thiostrepton results in less cross-linking. The cross-linking data suggests that the binding site for EF-G includes several proteins which are located at the interface between the 30-S and 50-S subunits.
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12
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Parmeggiani A, Sander G. Properties and regulation of the GTPase activities of elongation factors Tu and G, and of initiation factor 2. Mol Cell Biochem 1981; 35:129-58. [PMID: 6113539 DOI: 10.1007/bf02357085] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
During protein synthesis the interaction with ribosomes of elongation factors Tu (EF-Tu), G (EF-G) and initiation factor 2 (IF-2) is associated with the hydrolysis of GTP which is directly related to the functions of the factors. In this article we review systematically the properties of these GTPase activities in the presence and absence of protein synthesis, and by examining the characteristics of the different minimal systems for the expression of these activities we point to the role of the various effectors and to the enzymological aspects of the systems. For EF-Tu, it has been possible to eliminate any requirement for macromolecular effectors, showing that the factor itself is a GTPase. For EF-G, the presence of at least the 50S ribosomal subunit has remained a requirement, whereas IF-2 needs both the 50S and 30S subunits to exhibit GTPase activity. Between the GTPase activities of the three factors there are some striking similarities, but important differences prevail as a consequence of the specificity of the different functions. This can also be seen by examining the respective ribosomal regions implicated in these reactions. When coupled with protein synthesis, the three GTPase activities reveal characteristics differing from those observed in partial systems.
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13
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Alakhov YB, Zalite IK, Kashparov IA. Tyrosine residues in the C-terminal domain of the elongation factor G are essential for its interaction with the ribosome. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 105:531-8. [PMID: 6989608 DOI: 10.1111/j.1432-1033.1980.tb04529.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Chemical modification of the elongation factor G (EF-G) with tetranitromethane and iodine has been studied. It has been shown by spectrophotometric titration that EF-G contains two exposed tyrosine residues, one of which has an unusually low pK value for a phenol hydroxyl group at pH 8.5. Modification of one tyrosine residue with either tetranitromethane or iodine results in a 70--80% loss of EF-G activity in all ribosome-dependent reactions. Modification of three or four residues inhibits 90--100% of activity. Binding of EF-G with the 70-S ribosome and 50-S subunit is equally effective for protection of tyrosine residues against modification. The rate of EF-G modification with tetranitromethane is considerably higher in the presence of guanyl nucleotides than for free EF-G. The modified residues are located in the C-terminal domain of EF-G and are presumably contained in one of the sites of EF-G interaction with the ribosome.
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14
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Okonjo K. Effect of organic phosphates on the sulfhydryl reactivities of oxyhemoglobins A and S. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)85695-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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15
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Alakhov YB, Stengrevics OA, Filimonov VV, Venyaminov SY. Cleavage of elongation factor G into compact domains. EUROPEAN JOURNAL OF BIOCHEMISTRY 1979; 99:585-91. [PMID: 499218 DOI: 10.1111/j.1432-1033.1979.tb13291.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A limited trypsinolysis of native elongation factor G results in the formation of two large fragments resistant to further proteolysis. The fragments were isolated in homogeneous state in conditions when their native structure is retained. According to circular dichroism and scanning calorimetry data the formed fragments retain the stability and compact structure that they had in the whole protein.
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16
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Girshovich AS, Bochkareva ES, Kurtskhalia TV, Pozdnyakov VA, Ovchinnikov YA. Binding of GTP to elongation factor G by photoaffinity labeling. Methods Enzymol 1979; 60:726-45. [PMID: 459926 DOI: 10.1016/s0076-6879(79)60068-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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17
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Girshovich AS, Kurtskhalia TV. Use of the photoactivated analog of elongation factor G for the study of its interaction with ribosomes. Methods Enzymol 1979; 60:719-26. [PMID: 459925 DOI: 10.1016/s0076-6879(79)60067-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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18
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Kaziro Y. The role of guanosine 5'-triphosphate in polypeptide chain elongation. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 505:95-127. [PMID: 361078 DOI: 10.1016/0304-4173(78)90009-5] [Citation(s) in RCA: 473] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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19
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Sander G, Parlato G, Crechet JB, Nagel K, Parmeggiani A. Regulation of turnover GTPase activity of elongation factor G: the 30-S-coupled and 30-S-uncoupled reactions. Coordinated effects of cations, pH and polyamines. EUROPEAN JOURNAL OF BIOCHEMISTRY 1978; 86:555-63. [PMID: 26568 DOI: 10.1111/j.1432-1033.1978.tb12339.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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20
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Elongation factor G-dependent binding of a photoreactive GTP analogue to Escherichia coli ribosomes results in labeling of protein L11. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)40890-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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21
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ANALYSIS OF RIBOSOMAL TRANSLOCATION BY DRUGS. Gene Expr 1978. [DOI: 10.1016/b978-0-08-022624-8.50014-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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22
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Bermek E. Mechanisms in polypeptide chain elongation on ribosomes. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1978; 21:63-100. [PMID: 358280 DOI: 10.1016/s0079-6603(08)60267-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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23
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Girbes T, Campuzano S, Vźquez D, Modolell J. Effects of cations, antibiotics and other agents on the turnover of guanosine-nucleotide.elongation-factor-G.ribosome complexes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 81:483-90. [PMID: 340227 DOI: 10.1111/j.1432-1033.1977.tb11973.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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24
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Girbes T, Vázquez D, Modolell J. Detection of guanosine-nucleotide.elongation-factor-G complexes produced during the decay of guanosine-nucleotide.elongation-factor-G.Ribosome complexes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 81:473-81. [PMID: 340226 DOI: 10.1111/j.1432-1033.1977.tb11972.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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25
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San-Millán MJ, Vázquez D, Modolell J. The formation of guanosine-nucleotide - elongation-factor-G - ribosome complexes on free 70-S ribosomes, 50-S subunits, and polysomes. A comparative study. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 75:593-600. [PMID: 328279 DOI: 10.1111/j.1432-1033.1977.tb11559.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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26
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Rohrbach MS, Bodley JW. Selective chemical modification of Escherichia coli elongation factor G: butanedione modification of an arginine essential for nucleotide binding. Biochemistry 1977; 16:1360-3. [PMID: 14679 DOI: 10.1021/bi00626a019] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Treatment of Escherichia coli elongation factor G with the arginine reagent, 2,3-butanedione, leads to the inactivation of the enzyme when performed in sodium borate buffers. The inhibition follows pseudo-first-order kinetics until 95% of the activity has been lost and further incubation results in complete inhibiton. Removal of the borate by exhaustive dialysis results in the restoration of approximately 85% of the original activity. The pH dependence of the reaction suggests that the ionization of a group in the protein with a pKa of approximately 8.8 facilitates the reaction with butanedione. A reaction order of 1.01 +/- 0.13 was calculated for the inhibition reaction, indicating that the incorporation of one butanedione per elongation factor G results in the inactivation of the enzyme. The kinetics of inhibition in the presence of GTP indicate that the elongation factor G-GTP complex is refractory to butanedione inhibiton. Elongation factor G which has been partially inactivated by butanedione has the same apparent Km for GTP as does the native enzyme. These results indicate that elongation factor G contains only one essential arginine residue which is reactive with butanedione and that this residue is located at its nucleotide binding site.
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GIRSHOVICH AS, POZDNYAKOV VA, OVCHINNIKOV YA. Localization of the GTP-Binding Site in the Ribosome . Elongation-Factor-G . GTP Complex. ACTA ACUST UNITED AC 1976. [DOI: 10.1111/j.1432-1033.1976.tb10916.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Girbes T, Vazquez D, Modolell J. Polypeptide-chain elongation promoted by guanyl-5'-yl imidodiphosphate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1976; 67:257-65. [PMID: 786622 DOI: 10.1111/j.1432-1033.1976.tb10657.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In a purified system from Escherichia coli containing ribosomes complexed with poly(uridylic acid) and N-acetyl-phenylalanyl-tRNA, the nonhydrolyzable analog of GTP, guanyl-5'-yl imidodiphosphate (Guo-5'-P2-NH-P), promotes polypeptide synthesis at a rate several times slower than GTP. The activity is completely dependent on elongation factors EF-T (i.e, EF-Ts + EF-Tu) and EF-G. Examination of individual steps of the elongation cycle in partial reactions shows that Guo-5'-P2-NH-P is as efficient as GTP in promoting the EF-T-dependent binding of phenylalanyl-tRNA to the ribosomal A site. In contrast, Guo-5'-P2-NH-P promotes the translocation-dependent binding of phenylalanyl-tRNA to a ribosome complexed with A-site-bound N-acetyl-phenylalanyl-tRNA much more slowly than GTP. This slow rate of binding is due to the presence of EF-G on the ribosome, and not to sluggish translocation, since (a) the rate remains slow even after translocation of N-acetylphenylalanyl-tRNA is completed, (b) it is greatly speeded up by removal of EF-G from the reaction mixture (after translocation has occurred), and (c) it is slowed down again by readdition of the factor. Moreover, with post-translocated ribosomes and in the absence of EF-G, formation of dipeptide subsequent to the EF-T-dependent binding of phenylalanyl-tRNA is much slower when binding of this substrate has been promoted by Guo-5'-P2-NH-P than it is when promoted by GTP. The results suggest that, during polymerization with Guo-5'-P2-NH-P, EF-G and EF-Tu are slowly released from the ribosome and, consequently, the steps of the elongation cycle subsequent to translocation and aminoacyl-tRNA binding (aminoacyl-tRNA binding and peptide bond formation, respectively) are delayed. Thus, durong elongation cycle, GTP hydrolysis is probably essential for fast release of the factors from the ribosome.
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Girbes T, Vazquez D, Modolell J. A form of elongation factor G insensitive to N-ethyl-maleimide. Mol Biol Rep 1976; 2:401-6. [PMID: 775317 DOI: 10.1007/bf00366262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Treatment of elongation factor G (EF-G) with the thiol reagent N-ethylmaleimide only partially inhibits (10 to 70%) the activity of the factor in (a) guanosine nucleotide-EF-G-ribosome complex formation, (b) uncoupled ribosome-dependent GTP hydrolysis, and (c) polypeptide synthesis. Moreover, a similar treatment of the factor with N-[3H]ethylmaleimide does not lead to 3H-label being associated with a GDP-EF-G-ribosome-fusidic acid complex. Thus, the results indicate the presence in EF-G preparations of a form of the factor that does not react with N-ethylmaleimide.
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30
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Pullman B, Saran A. Quantum-mechanical studies on the conformation of nucleic acids and their constituents. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1976; 18:215-322. [PMID: 790473 DOI: 10.1016/s0079-6603(08)60589-9] [Citation(s) in RCA: 102] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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