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Chengguang H, Sabatini P, Brandi L, Giuliodori AM, Pon CL, Gualerzi CO. Ribosomal selection of mRNAs with degenerate initiation triplets. Nucleic Acids Res 2017; 45:7309-7325. [PMID: 28575317 PMCID: PMC5499595 DOI: 10.1093/nar/gkx472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 05/12/2017] [Indexed: 12/27/2022] Open
Abstract
To assess the influence of degenerate initiation triplets on mRNA recruitment by ribosomes, five mRNAs identical but for their start codon (AUG, GUG, UUG, AUU and AUA) were offered to a limiting amount of ribosomes, alone or in competition with an identical AUGmRNA bearing a mutation conferring different electrophoretic mobility to the product. Translational efficiency and competitiveness of test mRNAs toward this AUGmRNA were determined quantifying the relative amounts of the electrophoretically separated wt and mutated products synthesized in vitro and found to be influenced to different extents by the nature of their initiation triplet and by parameters such as temperature and nutrient availability in the medium. The behaviors of AUAmRNA, UUGmRNA and AUGmRNA were the same between 20 and 40°C whereas the GUG and AUUmRNAs were less active and competed poorly with the AUGmRNA, especially at low temperature. Nutrient limitation and preferential inhibition by ppGpp severely affected activity and competitiveness of all mRNAs bearing non-AUG starts, the UUGmRNA being the least affected. Overall, our data indicate that beyond these effects exclusively due to the degenerate start codons within an optimized translational initiation region, an important role is played by the context in which the rare start codons are present.
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Affiliation(s)
- He Chengguang
- College of Life Sciences, Engineering Research Centre of the Chinese Ministry of Education for Bioreactor and Pharmaceutical Development, Jilin Agricultural University, Changchun 130118, Jilin, China.,Laboratory of Genetics, University of Camerino 62032 Camerino, Italy
| | - Paola Sabatini
- Laboratory of Genetics, University of Camerino 62032 Camerino, Italy
| | - Letizia Brandi
- Laboratory of Genetics, University of Camerino 62032 Camerino, Italy
| | - Anna M Giuliodori
- Laboratory of Genetics, University of Camerino 62032 Camerino, Italy
| | - Cynthia L Pon
- Laboratory of Genetics, University of Camerino 62032 Camerino, Italy
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2
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Iwakura N, Yokoyama T, Quaglia F, Mitsuoka K, Mio K, Shigematsu H, Shirouzu M, Kaji A, Kaji H. Chemical and structural characterization of a model Post-Termination Complex (PoTC) for the ribosome recycling reaction: Evidence for the release of the mRNA by RRF and EF-G. PLoS One 2017; 12:e0177972. [PMID: 28542628 PMCID: PMC5443523 DOI: 10.1371/journal.pone.0177972] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 05/06/2017] [Indexed: 12/02/2022] Open
Abstract
A model Post-Termination Complex (PoTC) used for the discovery of Ribosome Recycling Factor (RRF) was purified and characterized by cryo-electron microscopic analysis and biochemical methods. We established that the model PoTC has mostly one tRNA, at the P/E or P/P position, together with one mRNA. The structural studies were supported by the biochemical measurement of bound tRNA and mRNA. Using this substrate, we establish that the release of tRNA, release of mRNA and splitting of ribosomal subunits occur during the recycling reaction. Order of these events is tRNA release first followed by mRNA release and splitting almost simultaneously. Moreover, we demonstrate that IF3 is not involved in any of the recycling reactions but simply prevents the re-association of split ribosomal subunits. Our finding demonstrates that the important function of RRF includes the release of mRNA, which is often missed by the use of a short ORF with the Shine-Dalgarno sequence near the termination site.
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Affiliation(s)
- Nobuhiro Iwakura
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, United States of America
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Takeshi Yokoyama
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Yokohama, Japan
| | - Fabio Quaglia
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, United States of America
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- University of Camerino, School of Biosciences and Veterinary Medicine, Camerino, Italy
| | - Kaoru Mitsuoka
- Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Osaka, Japan
| | - Kazuhiro Mio
- Molecular Profiling Research Center for Drug Discovery and OPERANDO Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan
| | - Hideki Shigematsu
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Yokohama, Japan
| | - Mikako Shirouzu
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Yokohama, Japan
| | - Akira Kaji
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (HK); (AK)
| | - Hideko Kaji
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, United States of America
- * E-mail: (HK); (AK)
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3
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Inhibition of translation initiation complex formation by GE81112 unravels a 16S rRNA structural switch involved in P-site decoding. Proc Natl Acad Sci U S A 2016; 113:E2286-95. [PMID: 27071098 DOI: 10.1073/pnas.1521156113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In prokaryotic systems, the initiation phase of protein synthesis is governed by the presence of initiation factors that guide the transition of the small ribosomal subunit (30S) from an unlocked preinitiation complex (30S preIC) to a locked initiation complex (30SIC) upon the formation of a correct codon-anticodon interaction in the peptidyl (P) site. Biochemical and structural characterization of GE81112, a translational inhibitor specific for the initiation phase, indicates that the main mechanism of action of this antibiotic is to prevent P-site decoding by stabilizing the anticodon stem loop of the initiator tRNA in a distorted conformation. This distortion stalls initiation in the unlocked 30S preIC state characterized by tighter IF3 binding and a reduced association rate for the 50S subunit. At the structural level we observe that in the presence of GE81112 the h44/h45/h24a interface, which is part of the IF3 binding site and forms ribosomal intersubunit bridges, preferentially adopts a disengaged conformation. Accordingly, the findings reveal that the dynamic equilibrium between the disengaged and engaged conformations of the h44/h45/h24a interface regulates the progression of protein synthesis, acting as a molecular switch that senses and couples the 30S P-site decoding step of translation initiation to the transition from an unlocked preIC to a locked 30SIC state.
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4
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Abstract
Selection of correct start codons on messenger RNAs is a key step required for faithful translation of the genetic message. Such a selection occurs in a complex process, during which a translation-competent ribosome assembles, eventually having in its P site a specialized methionyl-tRNAMet base-paired with the start codon on the mRNA. This chapter summarizes recent advances describing at the molecular level the successive steps involved in the process. Special emphasis is put on the roles of the three initiation factors and of the initiator tRNA, which are crucial for the efficiency and the specificity of the process. In particular, structural analyses concerning complexes containing ribosomal subunits, as well as detailed kinetic studies, have shed new light on the sequence of events leading to faithful initiation of protein synthesis in Bacteria.
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5
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Gualerzi C, Fabbretti A, Brandi L, Milon P, Pon C. Role of the Initiation Factors in mRNA Start Site Selection and fMet-tRNA Recruitment by Bacterial Ribosomes. Isr J Chem 2010. [DOI: 10.1002/ijch.201000006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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6
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Maar D, Liveris D, Sussman JK, Ringquist S, Moll I, Heredia N, Kil A, Bläsi U, Schwartz I, Simons RW. A single mutation in the IF3 N-terminal domain perturbs the fidelity of translation initiation at three levels. J Mol Biol 2008; 383:937-44. [PMID: 18805426 DOI: 10.1016/j.jmb.2008.09.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 08/30/2008] [Accepted: 09/05/2008] [Indexed: 11/28/2022]
Abstract
Bacterial translation initiation factor 3 (IF3) is involved in the fidelity of translation initiation at several levels, including start-codon discrimination, mRNA translation, and initiator-tRNA selection. The IF3 C-terminal domain (CTD) is required for binding to the 30S ribosomal subunit. N-terminal domain (NTD) function is less certain, but likely contributes to initiation fidelity. Point mutations in either domain can decrease initiation fidelity, but C-terminal domain mutations may be indirect. Here, the Y75N substitution mutation in the NTD is examined in vitro and in vivo. IF3(Y75N) protein binds 30S subunits normally, but is defective in start-codon discrimination, inhibition of initiation on leaderless mRNA, and initiator-tRNA selection, thereby establishing a direct role for the IF3 NTD in these initiation processes. A model illustrating how IF3 modulates an inherent function of the 30S subunit is discussed.
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Affiliation(s)
- Dianna Maar
- Department of Microbiology, Immunology, and Molecular Genetics, University of California-Los Angeles, 1602 Molecular Science, Los Angeles, CA 90095, USA
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7
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Studer SM, Joseph S. Unfolding of mRNA secondary structure by the bacterial translation initiation complex. Mol Cell 2006; 22:105-15. [PMID: 16600874 DOI: 10.1016/j.molcel.2006.02.014] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 01/25/2006] [Accepted: 02/07/2006] [Indexed: 10/24/2022]
Abstract
Translation initiation is a key step for regulating the level of numerous proteins within the cell. In bacteria, the 30S initiation complex directly binds to the translation initiation region (TIR) of the mRNA. How the ribosomal 30S subunit assembles on highly structured TIR is not known. Using fluorescence-based experiments, we assayed 12 different mRNAs that form secondary structures with various stabilities and contain Shine-Dalgarno (SD) sequences of different strengths. A strong correlation was observed between the stability of the mRNA structure and the association and dissociation rate constants. Interestingly, in the presence of initiation factors and initiator tRNA, the association kinetics of structured mRNAs showed two distinct phases. The second phase was found to be important for unfolding structured mRNAs to form a stable 30S initiation complex. We show that unfolding of structured mRNAs requires a SD sequence, the start codon, fMet-tRNA(fMet), and the GTP bound form of initiation factor 2 bound to the 30S subunit.
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MESH Headings
- Codon, Initiator/genetics
- Codon, Initiator/metabolism
- Eukaryotic Initiation Factor-2/metabolism
- Kinetics
- Nucleic Acid Conformation
- Peptide Chain Initiation, Translational
- Protein Biosynthesis
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Transfer, Met
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Affiliation(s)
- Sean M Studer
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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8
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Hirokawa G, Demeshkina N, Iwakura N, Kaji H, Kaji A. The ribosome-recycling step: consensus or controversy? Trends Biochem Sci 2006; 31:143-9. [PMID: 16487710 DOI: 10.1016/j.tibs.2006.01.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 01/13/2006] [Accepted: 01/31/2006] [Indexed: 10/25/2022]
Abstract
Ribosome recycling, the last step in translation, is now accepted as an essential process for prokaryotes. In 2005, three laboratories showed that ribosome-recycling factor (RRF) and elongation factor G (EF-G) cause dissociation of ribosomes into subunits, solving the long-standing problem of how this essential step of translation occurs. However, there remains ongoing controversy regarding the other actions of RRF and EF-G during ribosome recycling. We propose that the available data are consistent with the notion that RRF and EF-G not only split ribosomes into subunits but also participate directly in the release of deacylated tRNA and mRNA for the next round of translation.
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Affiliation(s)
- Go Hirokawa
- Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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9
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Hirokawa G, Nijman RM, Raj VS, Kaji H, Igarashi K, Kaji A. The role of ribosome recycling factor in dissociation of 70S ribosomes into subunits. RNA (NEW YORK, N.Y.) 2005; 11:1317-28. [PMID: 16043510 PMCID: PMC1370814 DOI: 10.1261/rna.2520405] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Protein synthesis is initiated on ribosomal subunits. However, it is not known how 70S ribosomes are dissociated into small and large subunits. Here we show that 70S ribosomes, as well as the model post-termination complexes, are dissociated into stable subunits by cooperative action of three translation factors: ribosome recycling factor (RRF), elongation factor G (EF-G), and initiation factor 3 (IF3). The subunit dissociation is stable enough to be detected by conventional sucrose density gradient centrifugation (SDGC). GTP, but not nonhydrolyzable GTP analog, is essential in this process. We found that RRF and EF-G alone transiently dissociate 70S ribosomes. However, the transient dissociation cannot be detected by SDGC. IF3 stabilizes the dissociation by binding to the transiently formed 30S subunits, preventing re-association back to 70S ribosomes. The three-factor-dependent stable dissociation of ribosomes into subunits completes the ribosome cycle and the resulting subunits are ready for the next round of translation.
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Affiliation(s)
- Go Hirokawa
- Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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10
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Allen GS, Zavialov A, Gursky R, Ehrenberg M, Frank J. The Cryo-EM Structure of a Translation Initiation Complex from Escherichia coli. Cell 2005; 121:703-12. [PMID: 15935757 DOI: 10.1016/j.cell.2005.03.023] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 03/14/2005] [Accepted: 03/22/2005] [Indexed: 11/22/2022]
Abstract
The 70S ribosome and its complement of factors required for initiation of translation in E. coli were purified separately and reassembled in vitro with GDPNP, producing a stable initiation complex (IC) stalled after 70S assembly. We have obtained a cryo-EM reconstruction of the IC showing IF2*GDPNP at the intersubunit cleft of the 70S ribosome. IF2*GDPNP contacts the 30S and 50S subunits as well as fMet-tRNA(fMet). IF2 here adopts a conformation radically different from that seen in the recent crystal structure of IF2. The C-terminal domain of IF2 binds to the single-stranded portion of fMet-tRNA(fMet), thereby forcing the tRNA into a novel orientation at the P site. The GTP binding domain of IF2 binds to the GTPase-associated center of the 50S subunit in a manner similar to EF-G and EF-Tu. Additionally, we present evidence for the localization of IF1, IF3, one C-terminal domain of L7/L12, and the N-terminal domain of IF2 in the initiation complex.
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Affiliation(s)
- Gregory S Allen
- Howard Hughes Medical Institute, Health Research, Inc. at the Wadsworth Center, Albany, New York 12201, USA
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11
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Raj VS, Kaji H, Kaji A. Interaction of RRF and EF-G from E. coli and T. thermophilus with ribosomes from both origins--insight into the mechanism of the ribosome recycling step. RNA (NEW YORK, N.Y.) 2005; 11:275-84. [PMID: 15661844 PMCID: PMC1370717 DOI: 10.1261/rna.7201805] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Accepted: 11/30/2004] [Indexed: 05/20/2023]
Abstract
Ribosome recycling factor (RRF), elongation factor-G (EF-G), and ribosomes from Thermus thermophilus (tt-) and Escherichia coli (ec-) were used to study the disassembly mechanism of post-termination ribosomal complexes by these factors. With tt-RRF, ec-EF-G can release bound-tRNA from ec-model post-termination complexes. However, tt-RRF is not released by ec-EF-G from ec-ribosomes. This complex with tt-RRF and ec-ribosomes after the tRNA release by ec-EF-G is regarded as an intermediate of the disassembly reaction. Not only tt-RRF, but also mRNA, cannot be released from ec-ribosomes by tt-RRF and ec-EF-G. These data suggest that the release of RRF from ribosomes is coupled or closely related to the release of mRNA during disassembly of post-termination complexes. With tt-ribosomes, ec-EF-G cannot release ribosome-bound ec-RRF even though they are from the same species, showing that proper interaction of ec-RRF and ec-EF-G does not occur on tt-ribosomes. On the other hand, in contrast to a published report, tt-EF-G functions with ec-RRF to disassemble ec-post-termination complexes. In support of this finding, tt-EF-G translocates peptidyl tRNA on ec-ribosomes and catalyzes ec-ribosome-dependent GTPase, showing that tt-EF-G has in vitro translocation activity with ec-ribosomes. Since tt-EF-G with ec-RRF can release tRNA from ec-post-termination complexes, the data are consistent with the hypothesis that the release of tRNA by RRF and EF-G from post-termination complexes is a result of a translocation-like activity of EF-G on RRF.
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Affiliation(s)
- V Samuel Raj
- Department of Microbiology, School of Medicine, University of Pennsylvania, Room 203B, Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA
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12
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Kaji A, Kiel MC, Hirokawa G, Muto AR, Inokuchi Y, Kaji H. The fourth step of protein synthesis: disassembly of the posttermination complex is catalyzed by elongation factor G and ribosome recycling factor, a near-perfect mimic of tRNA. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 66:515-29. [PMID: 12762054 DOI: 10.1101/sqb.2001.66.515] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- A Kaji
- Microbiology Department, Medical School, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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13
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Petrelli D, LaTeana A, Garofalo C, Spurio R, Pon CL, Gualerzi CO. Translation initiation factor IF3: two domains, five functions, one mechanism? EMBO J 2001; 20:4560-9. [PMID: 11500382 PMCID: PMC125572 DOI: 10.1093/emboj/20.16.4560] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Initiation factor IF3 contains two domains separated by a flexible linker. While the isolated N-domain displayed neither affinity for ribosomes nor a detectable function, the isolated C-domain, added in amounts compensating for its reduced affinity for 30S subunits, performed all activities of intact IF3, namely: (i) dissociation of 70S ribosomes; (ii) shift of 30S-bound mRNA from 'stand-by' to 'P-decoding' site; (iii) dissociation of 30S-poly(U)-NacPhe-tRNA pseudo- initiation complexes; (iv) dissociation of fMet-tRNA from initiation complexes containing mRNA with the non-canonical initiation triplet AUU (AUUmRNA); (v) stimulation of mRNA translation regardless of its start codon and inhibition of AUUmRNA translation at high IF3C/ribosome ratios. These results indicate that while IF3 performs all its functions through a C-domain-30S interaction, the N-domain function is to provide additional binding energy so that its fluctuating interaction with the 30S subunit can modulate the thermodynamic stability of the 30S-IF3 complex and IF3 recycling. The localization of IF3C far away from the decoding site and anticodon stem-loop of P-site-bound tRNA indicates that the IF3 fidelity function does not entail its direct contact with these structures.
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Affiliation(s)
- Dezemona Petrelli
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
| | - Anna LaTeana
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
| | - Cristiana Garofalo
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
| | - Roberto Spurio
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
| | - Cynthia L. Pon
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
| | - Claudio O. Gualerzi
- Laboratory of Genetics, Department of Biology MCA, University of Camerino, I-62032 Camerino (MC) and Institute of Biochemistry, University of Ancona, I-60131 Ancona, Italy Corresponding author e-mail
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14
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Al-Karadaghi S, Kristensen O, Liljas A. A decade of progress in understanding the structural basis of protein synthesis. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2001; 73:167-93. [PMID: 10958930 DOI: 10.1016/s0079-6107(00)00005-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The key reaction of protein synthesis, peptidyl transfer, is catalysed in all living organisms by the ribosome - an advanced and highly efficient molecular machine. During the last decade extensive X-ray crystallographic and NMR studies of the three-dimensional structure of ribosomal proteins, ribosomal RNA components and their complexes with ribosomal proteins, and of several translation factors in different functional states have taken us to a new level of understanding of the mechanism of function of the protein synthesis machinery. Among the new remarkable features revealed by structural studies, is the mimicry of the tRNA molecule by elongation factor G, ribosomal recycling factor and the eukaryotic release factor 1. Several other translation factors, for which three-dimensional structures are not yet known, are also expected to show some form of tRNA mimicry. The efforts of several crystallographic and biochemical groups have resulted in the determination by X-ray crystallography of the structures of the 30S and 50S subunits at moderate resolution, and of the structure of the 70S subunit both by X-ray crystallography and cryo-electron microscopy (EM). In addition, low resolution cryo-EM models of the ribosome with different translation factors and tRNA have been obtained. The new ribosomal models allowed for the first time a clear identification of the functional centres of the ribosome and of the binding sites for tRNA and ribosomal proteins with known three-dimensional structure. The new structural data have opened a way for the design of new experiments aimed at deeper understanding at an atomic level of the dynamics of the system.
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Affiliation(s)
- S Al-Karadaghi
- Department of Molecular Biophysics, Lund University, Box 124, 221 00, Lund, Sweden.
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15
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Atarashi K, Kaji A. Inhibitory effect of heterologous ribosome recycling factor on growth of Escherichia coli. J Bacteriol 2000; 182:6154-60. [PMID: 11029437 PMCID: PMC94751 DOI: 10.1128/jb.182.21.6154-6160.2000] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ribosome recycling factor (RRF) of Thermotoga maritima was expressed in Escherichia coli from the cloned T. maritima RRF gene and purified. Expression of T. maritima RRF inhibited growth of the E. coli host in a dose-dependent manner, an effect counteracted by the overexpression of E. coli RRF. T. maritima RRF also inhibited the E. coli RRF reaction in vitro. Genes encoding RRFs from Streptococcus pneumoniae and Helicobacter pylori have been cloned, and they also impair growth of E. coli, although the inhibitory effect of these RRFs was less pronounced than that of T. maritima RRF. The amino acid sequence at positions 57 to 62, 74 to 78, 118 to 122, 154 to 160, and 172 to 176 in T. maritima RRF differed totally from that of E. coli RRF. This suggests that these regions are important for the inhibitory effect of heterologous RRF. We further suggest that bending and stretching of the RRF molecule at the hinge between two domains may be critical for RRF activity and therefore responsible for T. maritima RRF inhibition of the E. coli RRF reaction.
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Affiliation(s)
- K Atarashi
- Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia 19104, USA
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16
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Inokuchi Y, Hirashima A, Sekine Y, Janosi L, Kaji A. Role of ribosome recycling factor (RRF) in translational coupling. EMBO J 2000; 19:3788-98. [PMID: 10899132 PMCID: PMC313962 DOI: 10.1093/emboj/19.14.3788] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
RNA phage GA coat and lysis protein expression are translationally coupled through an overlapping termination and initiation codon UAAUG. Essential for this coupling are the proximity of the termination codon of the upstream coat gene to the initiation codon of the lysis gene (either a <3 nucleotide separation or physical closeness through a possible hairpin structure) but not the Shine-Dalgarno sequence. This suggests that the ribosomes completing the coat gene translation are exclusively responsible for translation of the lysis gene. Inactivation of ribosome recycling factor (RRF), which normally releases ribosomes at the termination codon, did not influence the expression of the reporter gene fused to the lysis gene. This suggests the possibility that RRF may not release ribosomes from the junction UAAUG. However, RRF is essential for correct ribosomal recognition of the AUG codon as the initiation site for the lysis gene.
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MESH Headings
- Amino Acid Sequence
- Bacteriophages/genetics
- Bacteriophages/metabolism
- Base Sequence
- Capsid/biosynthesis
- Capsid/genetics
- Codon, Initiator/genetics
- Codon, Terminator/genetics
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Escherichia coli/virology
- Gene Expression Regulation, Viral
- Genes, Reporter/genetics
- Genes, Viral/genetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Biosynthesis
- Proteins/genetics
- Proteins/metabolism
- RNA Viruses/genetics
- RNA Viruses/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Ribosomal Proteins
- Ribosomes/genetics
- Ribosomes/metabolism
- Sequence Analysis, Protein
- Sequence Deletion
- Substrate Specificity
- Viral Proteins/biosynthesis
- Viral Proteins/genetics
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Affiliation(s)
- Y Inokuchi
- Department of Bioscience, Teikyo University, Utsunomiya 320-8551, Yakult Pharmaceutical Inc. Co. Tokyo, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan
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17
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Meunier S, Spurio R, Czisch M, Wechselberger R, Guenneugues M, Gualerzi CO, Boelens R. Structure of the fMet-tRNA(fMet)-binding domain of B. stearothermophilus initiation factor IF2. EMBO J 2000; 19:1918-26. [PMID: 10775275 PMCID: PMC302012 DOI: 10.1093/emboj/19.8.1918] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The three-dimensional structure of the fMet-tRNA(fMet) -binding domain of translation initiation factor IF2 from Bacillus stearothermophilus has been determined by heteronuclear NMR spectroscopy. Its structure consists of six antiparallel beta-strands, connected via loops, and forms a closed beta-barrel similar to domain II of elongation factors EF-Tu and EF-G, despite low sequence homology. Two structures of the ternary complexes of the EF-Tu small middle dotaminoacyl-tRNA small middle dot GDP analogue have been reported and were used to propose and discuss the possible fMet-tRNA(fMet)-binding site of IF2.
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Affiliation(s)
- S Meunier
- Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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18
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Selmer M, Al-Karadaghi S, Hirokawa G, Kaji A, Liljas A. Crystal structure of Thermotoga maritima ribosome recycling factor: a tRNA mimic. Science 1999; 286:2349-52. [PMID: 10600747 DOI: 10.1126/science.286.5448.2349] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Ribosome recycling factor (RRF), together with elongation factor G (EF-G), catalyzes recycling of ribosomes after one round of protein synthesis. The crystal structure of RRF was determined at 2.55 angstrom resolution. The protein has an unusual fold where domain I is a long three-helix bundle and domain II is a three-layer beta/alpha/beta sandwich. The molecule superimposes almost perfectly with a transfer RNA (tRNA) except that the amino acid-binding 3' end is missing. The mimicry suggests that RRF interacts with the posttermination ribosomal complex in a similar manner to a tRNA, leading to disassembly of the complex. The structural arrangement of this mimicry is entirely different from that of other cases of less pronounced mimicry of tRNA so far described.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Crystallography, X-Ray
- Models, Molecular
- Molecular Mimicry
- Molecular Sequence Data
- Nucleic Acid Conformation
- Peptide Elongation Factor G/chemistry
- Protein Biosynthesis
- Protein Conformation
- Protein Folding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Proteins/chemistry
- Proteins/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/metabolism
- RNA, Transfer, Phe/chemistry
- RNA, Transfer, Phe/metabolism
- Ribosomal Proteins
- Ribosomes/metabolism
- Sequence Alignment
- Thermotoga maritima/chemistry
- Thermotoga maritima/metabolism
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Affiliation(s)
- M Selmer
- Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, Post Office Box 124, SE-22100 Lund, Sweden
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19
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de Cock E, Springer M, Dardel F. The interdomain linker of Escherichia coli initiation factor IF3: a possible trigger of translation initiation specificity. Mol Microbiol 1999; 32:193-202. [PMID: 10216872 DOI: 10.1046/j.1365-2958.1999.01350.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Initiation factor IF3 is responsible for the accuracy of translation initiation in bacteria, by destabilizing complexes involving non-initiator tRNA and/or nonstart codons. This proofreading is performed on the 30S subunit to which IF3 binds selectively. IF3 has an unusual architecture, with two globular domains connected by a mobile, positively charged linker. Here, we have investigated the function of this flexible tether by probing its conformation when IF3 is bound to the ribosomal RNA. Using site-directed mutagenesis of the linker region, we have also selectively modified its length, its flexibility and its chemical composition. The function of the mutant genes was assayed in vivo, and the structural and biochemical properties of some of the corresponding variant proteins were characterized in vitro. The two isolated domains of IF3 were also co-expressed in order to test the requirement for their covalent attachment. The results indicate that the physical link between the two domains of IF3 is essential for the function of this protein, but that the exact length and chemical composition of the linker can be varied to a large extent. A model is presented in which the extended linker would act as a 'strap', triggering a conformational change in the 30S subunit, which would then ensure initiator tRNA selection.
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Affiliation(s)
- E de Cock
- Laboratoire de Biochimie, UMR 7654 du CNRS, Palaiseau, France
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20
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Schmitt E, Guillon JM, Meinnel T, Mechulam Y, Dardel F, Blanquet S. Molecular recognition governing the initiation of translation in Escherichia coli. A review. Biochimie 1996; 78:543-54. [PMID: 8955898 DOI: 10.1016/s0300-9084(96)80001-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Selection of the proper start codon for the synthesis of a polypeptide by the Escherichia coli translation initiation apparatus involves several macromolecular components. These macromolecules interact in a specific and concerted manner to yield the translation initiation complex. This review focuses on recent data concerning the properties of the initiator tRNA and of enzymes and factors involved in the translation initiation process. The three initiation factors, as well as methionyl-tRNA synthetase and methionyl-tRNA(f)Met formyltransferase are described. In addition, the tRNA recognition properties of EF-Tu and peptidyl-tRNA hydrolase are considered. Finally, peptide deformylase and methionine aminopeptidase, which catalyze the amino terminal maturation of nascent polypeptides, can also be associated to the translation initiation process.
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Affiliation(s)
- E Schmitt
- Laboratoire de Biochimie, URA-CNRS no 1970, Ecole Polytechnique, Palaiseau, France
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21
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La Teana A, Pon CL, Gualerzi CO. Translation of mRNAs with degenerate initiation triplet AUU displays high initiation factor 2 dependence and is subject to initiation factor 3 repression. Proc Natl Acad Sci U S A 1993; 90:4161-5. [PMID: 8483930 PMCID: PMC46466 DOI: 10.1073/pnas.90.9.4161] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The influence of the rare initiation triplet AUU on mRNA translation was investigated by comparing the activity of two pairs of model mRNAs that differ in the length of Shine-Dalgarno and spacer sequences. Irrespective of the initiation triplet (AUG or AUU), all mRNAs had similar template activity in vitro, but translation of AUU mRNAs depended more on initiation factor (IF) 2 and less on IF3 than that of AUG mRNAs. Increasing the IF3/ribosome ratio from 2 to 10 progressively inhibited the AUU mRNAs and abolished their capacity to compete for translating ribosomes with other mRNAs but did not affect activity of the AUG mRNAs. The effects induced by IF3 are from its different influence on on- and off-rates of the transition 30S preinitiation complex<==>30S initiation complex; depending on the nature of the initiation triplet (AUG or AUU) of the mRNA, IF3 shifts the position of equilibrium toward binding or dissociation of fMet-tRNA, respectively. Stimulation of fMet-tRNA binding and dissociation yields superimposable IF3 titration curves that saturate at an IF3/30S ratio of approximately 1, indicating that the data are from the interaction of one molecule of IF3 with the same 30S binding site. Both effects are either lost or strongly reduced with 30S mutants defective in IF3 binding. Translational repression of AUU mRNAs by IF3 is from the factor-dependent dissociation of fMet-tRNA from 30S subunits, which becomes relevant when excess IF3 interferes with the formation of 70S initiation complex, presumably by interacting with 50S subunit.
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Affiliation(s)
- A La Teana
- Department of Biology, University of Camerino, Italy
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22
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Abstract
Bacteriophage lysis involves at least two fundamentally different strategies. Most phages elaborate at least two proteins, one of which is a murein hydrolase, or lysin, and the other is a membrane protein, which is given the designation holin in this review. The function of the holin is to create a lesion in the cytoplasmic membrane through which the murein hydrolase passes to gain access to the murein layer. This is necessary because phage-encoded lysins never have secretory signal sequences and are thus incapable of unassisted escape from the cytoplasm. The holins, whose prototype is the lambda S protein, share a common organization in terms of the arrangement of charged and hydrophobic residues, and they may all contain at least two transmembrane helical domains. The available evidence suggests that holins oligomerize to form nonspecific holes and that this hole-forming step is the regulated step in phage lysis. The correct scheduling of the lysis event is as much an essential feature of holin function as is the hole formation itself. In the second strategy of lysis, used by the small single-stranded DNA phage phi X174 and the single-stranded RNA phage MS2, no murein hydrolase activity is synthesized. Instead, there is a single species of small membrane protein, unlike the holins in primary structure, which somehow causes disruption of the envelope. These lysis proteins function by activation of cellular autolysins. A host locus is required for the lytic function of the phi X174 lysis gene E.
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Affiliation(s)
- R Young
- Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843
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23
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Adhin MR, van Duin J. Translational regulation of the lysis gene in RNA bacteriophage fr requires a UUG initiation codon. MOLECULAR & GENERAL GENETICS : MGG 1989; 218:137-42. [PMID: 2779514 DOI: 10.1007/bf00330576] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Single nucleotide substitutions identify a UUG triplet as the initiation codon of the lysis gene in RNA bacteriophage fr. This initiation codon is non-functional in de novo initiation but is activated by translational termination at the overlapping coat gene. The UUG initiation codon is crucial for gene regulation in the phage, as it excludes uncontrolled access of ribosomes to the start of the lysis gene. Replacement of UUG by either GUG or AUG results in the loss of genetic control of the lysis gene. A model is presented in which initiation factor IF3 proofreads de novo initiation at UUG codons.
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Affiliation(s)
- M R Adhin
- Department of Biochemistry, Leiden University, Gorlaeus Laboratoria, The Netherlands
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24
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Denslow ND, LiCata VJ, Gualerzi C, O'Brien TW. Interaction of bovine mitochondrial ribosomes with Escherichia coli initiation factor 3 (IF3). Biochemistry 1988; 27:3521-7. [PMID: 3291951 DOI: 10.1021/bi00409a059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mammalian mitochondrial ribosomes are distinguished from their bacterial and eukaryotic-cytoplasmic counterparts, as well as from mitochondrial ribosomes of lower eukaryotes, by their physical and chemical properties and their high protein content. However, they do share more functional homologies with bacterial ribosomes than with cytoplasmic ribosomes. To search for possible homologies between mammalian mitochondrial ribosomes and bacterial ribosomes at the level of initiation factor binding sites, we studied the interaction of Escherichia coli initiation factor 3 (IF3) with bovine mitochondrial ribosomes. Bacterial IF3 was found to bind to the small subunit of bovine mitochondrial ribosomes with an affinity of the same order of magnitude as that for bacterial ribosomes, suggesting that most of the functional groups contributing to the IF3 binding site in bacterial ribosomes are conserved in mitochondrial ribosomes. Increasing ionic strength affects binding to both ribosomes similarly and suggests a large electrostatic contribution to the reaction. Furthermore, bacterial IF3 inhibits the Mg2+-dependent association of mitochondrial ribosomal subunits, suggesting that the bacterial IF3 binds to mitochondrial small subunits in a functional way.
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Affiliation(s)
- N D Denslow
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville 32601-0245
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25
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Berkhout B, van der Laken CJ, van Knippenberg PH. Formylmethionyl-tRNA binding to 30 S ribosomes programmed with homopolynucleotides and the effect of translational initiation factor 3. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 866:144-53. [PMID: 3513840 DOI: 10.1016/0167-4781(86)90111-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Binding of the polynucleotides poly(U), poly(X) and poly(dT) to 30 S ribosomes of Escherichia coli triggers IF2-dependent binding of initiator-tRNA (fMet-tRNA) to these particles. Poly(A) and poly(C) are inactive. A minimum chain-length of approximately 100 residues in poly(U) is required for full activity in fMet-tRNA binding, although much shorter polymers bind tightly to 30 S particles and do stimulate the binding of acPhe-tRNA. The stimulation of fMet-tRNA binding to 30 S ribosomes is strongly reduced under conditions where the polynucleotides adopt secondary structure. Complexes containing fMet-tRNA and the non-cognate codon UUU or XXX are destabilized by IF3, whereas the formation of such a complex containing an AUG codon is slightly enhanced by the factor. Consistent with previous observations, it was found that all model initiation complexes containing acPhe-tRNA are strongly destabilized by IF3, even when the cognate codon (UUU) is present. Our results suggest that IF3 counteracts 'unnatural' initiation events in vitro and suggest a regulatory role for this factor in vivo.
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26
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Giri L, Pon CL, Gualerzi C, Doster W, Hess B. Hydrodynamic studies on the Escherichia coli 30S ribosomal subunits and 30S.IF-3 complex. Biochem Biophys Res Commun 1979; 87:976-82. [PMID: 380562 DOI: 10.1016/s0006-291x(79)80002-9] [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: 12/14/2022]
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27
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Mechanism of the spontaneous and initiation factor 3-induced dissociation of 30 S.aminoacyl-tRNA.polynucleotide ternary complexes. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30269-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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28
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Pon CL, Brimacombe R, Gualerzi C. Cross-linking of Escherichia coli initiation factor IF-3 to the RNA moiety of the 30S ribosomal subunits. Biochemistry 1977; 16:5681-6. [PMID: 412517 DOI: 10.1021/bi00645a005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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29
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Ewald R, Gualer C. Structure-function relationship in Escherichia coli initiation factors. I. Phosphorylation of IF-3 by coliphage T7 protein kinase. Biochem Biophys Res Commun 1977; 77:1517-24. [PMID: 332180 DOI: 10.1016/s0006-291x(77)80150-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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30
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Gualerzi C, Risuleo G, Pon CL. Initial rate kinetic analysis of the mechanism of initiation complex formation and the role of initiation factor IF-3. Biochemistry 1977; 16:1684-9. [PMID: 322704 DOI: 10.1021/bi00627a025] [Citation(s) in RCA: 85] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Initial rate kinetics of the formation of ternary complexes of Escherichia coli 30S ribosomal subunits, poly(uridylic acid), and N-acetylphenylalanyl transfer ribonucleic acid in the presence and in the absence of IF-3 are consistent with the hypothesis that the ternary complex is formed through a random order of addition of polynucleotide and aminoacyl-tRNA to separate and independent binding sites on the 30S ribosomes. The transformation of an intermediate into a stable ternary complex which probably entails a rearrangement of the ribosome structure leading to a codon-anticodon interaction represents the rate-limiting step in the formation of the ternary complex. The rate constant of this transformation, as well as the association constants for the formation of the 30S-poly(U) and 30S-N-AcPhe-tRNA binary complexes, are enhanced by the presence of IF-3 which acts as a kinetic effector on reactions which are intrinsic properties of the 30S ribosome. The IF-3-induced modification of these kinetic parameters of the 30S ribosomal subunit can per se explain the effect of IF-3 on protein synthesis without invoking a specific action at the level of the mRNA-ribosome interaction. This seems to be confirmed by the finding that IF-3 can stimulate several-fold the formation of a ternary complex even if one by-passes the ribosome-template binding step by starting with a covalent 30S-polynucleotide binary complex. Furthermore, the above-mentioned changes induced by IF-3 appear to be compatible with the previously proposed idea that the binding of the factor modifies the conformation of the 30S subunit. The random order of addition of substrates determined for the 30S-N-AcPhe-tRNA-poly(U) model system was found to be valid also for the more physiological 30S initiation complex containing poly(A,U.G) and (fMet-tRNA formed at low Mg2+ concentration in the presence of GTP and all three initiation factors.
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31
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Legualt-Démare L, Chambliss GH. Selective messenger translation by Bacillus subtilis ribosomes. MOLECULAR & GENERAL GENETICS : MGG 1976; 142:277-87. [PMID: 818501 DOI: 10.1007/bf00271252] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The in vitro B. subtilis protein synthesizing system is very restricted in its ability to translate E. coli phage messenger RNA's, specifically phage T4 RNA, even though it actively translates its proper mRNA species. In contrast, the E. coli system translates with similar efficiency mRNA from either source. The initiation factors from the two systems are functionally interchangeable. The 30S B. subtilis ribosomal subunit is responsible for the limited template specificity of the B. subtilis ribosomes. Although the efficiency of the T4RNA directed F Met-tRNA binding by B. subtilis ribosomes is less than that of SPOI RNA-directed binding, the most restrictive step in the translation of T4RNA by B. subtilis ribosomes appears to be at the level of the formation of the first peptide bond, as measured by F Metpuromycin formation.
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32
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Michalski CJ, Sells BH, Wahba AJ. Molecular morphology of ribosomes: effect of chain initiation factor 3 on 30 S subunit conformation. FEBS Lett 1976; 71:347-50. [PMID: 793863 DOI: 10.1016/0014-5793(76)80967-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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33
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Ewald R, Pon C, Gualerzi C. Reactivity of ribosomal sulfhydryl groups in 30S ribosomal subunits of Escherichia coli and 30S-IF-3 complexes. Biochemistry 1976; 15:4786-91. [PMID: 791359 DOI: 10.1021/bi00667a006] [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: 12/24/2022]
Abstract
The reaction of 30S subunits with the SH group reagent N-ethylmaleimide (NEM) causes the loss of approximately 60% of their synethetic activity, but has little or no effect on the ribosomal binding of initiation factor IF-3. The ribosomal binding of this factor, on the other hand, was found to significantly influence the rate and the extent to which several 30S ribosomal proteins react with radioactively labeled NEM when the reaction kinetics of individual ribosomal proteins toward NEM were compared in 30S and 30S-IF-3 complexes. Of the nine 30S ribosomal proteins which react with NEM, proteins S1, S11, S12, and S18 were found to have lower reactivities, while proteins S4 and S21 displayed higher reactivity in the presence of IF-3. The reactivity of proteins S8, S13, and S17, on the other hand, appeared to be influenced little or not at all by the presence of the factor. These results are interpreted as supporting evidence for the premise that the binding of IF-3 results in a conformational change of the 30S subunit.
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34
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Ohsawa H, Maruo B. Restoration by ribosomal protein S1 of the defective translation in a temperature-sensitive mutant of Escherichia coli K-12: characterization and genetic studies. J Bacteriol 1976; 127:1157-66. [PMID: 783133 PMCID: PMC232907 DOI: 10.1128/jb.127.3.1157-1166.1976] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
A temperature-sensitive mutant of Escherichia coli was isolated that had a temperature-sensitive defect in ribosomal-wash protein(s) required for translation in vitro of E. coli endogenous messenger ribonucleic acid. It was found that 30S ribosomal protein S1 rescued the defect in the ribosomal-wash protein(s) of the mutant and that the complete restoration to the wild-type level was attained when 1 mol of protein S1 was added to 1 mol of 70S ribosome. The mutation, tss, causing such a defect was mapped at 21 min and was closely linked to the pyrD locus, the region of which was entirely different from that of the other genes coding for the many ribosomal proteins of E. coli. These results indicate that the gene specified by this mutation is involved in the function of the 30S ribosomal protein S1.
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35
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Risuleo G, Gualerzi C, Pon C. Specificity and properties of the destabilization, induced by initiation factor IF-3, of ternary complexes of the 30-S ribosomal subunit, aminoacyl-tRNA and polynucleotides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1976; 67:603-13. [PMID: 9282 DOI: 10.1111/j.1432-1033.1976.tb10726.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Initiation factor IF-3 causes the destabilization of preformed ternary complexes of 30-S ribosomal subunit, codons and aminoacyl-tRNAs or peptidyl-tRNA. This destabilization is dilution-dependent and affects all ternary complexes with the exception of those containing the initiator fMet-tRNA, which remain more resistant to IF-3-induced destabilization under the various conditions studied. Several possible reasons for this specificity have been examined. It was found that the basis for the specificity is not: (a) an intrinsic greater stability of the ternary complexes containing fMet-tRNA, (b) the amoung of aminoacyl-tRNA bound to the ribosome, (c) the conditions under which the ternary complex is made or (d) the formylation of the amino group. On the other hand, the nature of the polynucleotide in response to which the ternary complex is formed was found to influence the amount of aminoacyl-tRan bound to the ribosome, and to some extent the amount of aminoacyl-tRNA which can be relased. The ternary complex containing the mischarged initiator tRNA fVal-tRNAfMet displays greater resistance to the IF-3-induced destabilization than the complex containing fVal-tRNAVal. These results indicate that the specificity of the IF-3 activity is due to the special structural feature of the initiator tRNA molecule and to some extent to the nature of the polynucleotide. The IF-3-induced destabilization of ternary complexes was found to be little affected by variations in reaction conditons, so that this IF-3 activity can be used to measure the stoichiometric binding of IF-3 to the ribosome over a broad range of pH and K+ and Mg2+ concentrations. Several antibiotics have been tested for their capacity to interfere with this reaction; only high concentrations of tetracycline blocked this IF-3 activity.
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36
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Kay AC, Graffe M, Grunberg-Manago M. Purification and properties of two initiation factors from Bacillus stearothermophilus. Biochimie 1976; 58:183-99. [PMID: 782553 DOI: 10.1016/s0300-9084(76)80369-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Two initiation factors have been isolated from the thermophilic bacterium, Bacillus stearothermophilus, and purified to near homogeneity. The two factors possess physical characteristics and activities associated with the E. coli initiation factors IF-2 and IF-3, and are interchangeable with these factors. The two systems present, however, several differences : S-IF-2 is significantly more heat stable than E. coli IF-2, loosing less than 50 per cent of its activity after 20 minutes at 70degreesC. S-IF-2 alone is unable to promote initiation complex formation on B. stearothermophilus or E. coli ribosomes, and S-IF-3 is absolutely necessary for initiation of complex formation on B. stearothermophilus ribosomes. No factor corresponding to IF-1 has been found. S-IF-3 appears to be able to replace at least partially IF-1, since S-IF-3 and E. coli IF-2 are sufficient to promote maximum fMet-tRNA binding to E. coli ribosomes, while E. coli IF-3 and IF-2 also require IF-1. The differences between the two systems are perhaps required because of the elevated temperature at which B. stearothermophilus normally grows.
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37
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Ponta H, Pon CL, Herrlich P, Gualerzi C, Hirsch-Kauffmann M, Pfennig-Yeh ML, rahmsdorf HJ, Schweiger M. The sex-factor-dependent exclusion of coli virus T7. EUROPEAN JOURNAL OF BIOCHEMISTRY 1975; 59:261-70. [PMID: 1204611 DOI: 10.1111/j.1432-1033.1975.tb02450.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The cause of T7 exclusion by the F episome was investigated. Extracts from neither normal nor infected F+ cells contained an inhibitor of gene expression in vitro. The protein synthesizing systems prepared in vitro from these cells supported T7 early and late protein synthesis with normal efficiency. The content of translational initiation factors in F- and F+ cells, both noninfected and infected, was almost identical. The episome-dependent block of T7 gene expression was observed only in intact cells and detailed kinetics of gene expression in vivo revealed a stop of all transcription and translation at or just before 11 min after T7 infection. The mechanism of F+-dependent T7 exclusion involves both episomal and viral gene products. The data indicate that a T7-induced membrane alteration of the F+ cell membrane leads to cessation of T7 development as well as to the death of the host cell ('suicide').
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38
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Ranu RS, Wool IG. Discrimination between eukaryotic and prokaryotic, and formylated and non-formylated, initiator tRNAs by eukaryotic initiation factor EIF-3. Nature 1975; 257:616-8. [PMID: 1101076 DOI: 10.1038/257616a0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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39
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Ogawa K, Kaji A. Requirement for ribosome-releasing factor for the release of ribosomes at the termination codon. EUROPEAN JOURNAL OF BIOCHEMISTRY 1975; 58:411-9. [PMID: 1183444 DOI: 10.1111/j.1432-1033.1975.tb02388.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
With the use of 3H-labeled R 17 amB2 phage RNA having an UAG codon at the seventh triplet of the coat cistron, release of the RNA from ribosomes at the termination codon was studied. The ribosome-releasing factor previously described was shown to stimulate the process of mRNA release at the termination factor (RF-1). GTP was required for this process and guanosine 5'-(beta,gamma-methylene)triphosphate could not replace GTP. No apparent change of size of R 17 RNA was observed during the release of the R 17 RNA from the ribosomes. The ribosome-releasing factor is distinct from the known termination codon-specific factor such as RF-1.
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Ogawa K, Kaji A. Ribosome run through of the termination codon in the absence of the ribosome releasing factor. BIOCHIMICA ET BIOPHYSICA ACTA 1975; 402:288-96. [PMID: 1100117 DOI: 10.1016/0005-2787(75)90266-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The ribosome releasing factor (RR factor) which releases ribosomes from mRNA at the termination codon has been examined for its effects on the amino acid incorporation programmed by wild type R17 Phage RNA and amB2 R17 RNA. When RR factor was added at the beginning of the incorporation, there was no effect on the initial rate of incorporation but it reduced the final level of incorporation. The reduction of the final level of incorporation was more pronounced for histidine incorporation than for valine incorporation suggesting that the translation of the RNA polymerase cistron was more influenced by RR factor. These experiments were carried out under conditions where no reinitiation of protein synthesis occurred. In the presence of RR factor, suppressor tRNA functioned better for the incorporation of amino acids into proteins with amB2 R17 RNA than did wild type tRNA. No such differential effect of suppressor tRNA was observed in the absence of RR factor. This suggests that the ribosome has to be released from mRNA by RR factor in order for the amber mutation to be effective.
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Gualerzi C, Grandolfo M, Paradies HH, Pon C. Letter to the editor: Circular dichroism analysis of the ribosomal binding of initiation factor IF-3. J Mol Biol 1975; 95:569-73. [PMID: 1097719 DOI: 10.1016/0022-2836(75)90318-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Pon CL, Gualerzi C. Effect of initiation factor 3 binding on the 30S ribosomal subunits of Escherichia coli. Proc Natl Acad Sci U S A 1974; 71:4950-4. [PMID: 4612534 PMCID: PMC434017 DOI: 10.1073/pnas.71.12.4950] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Under certain conditions, initiation factor 3 (IF-3) can cause the release of aminoacyl-tRNA bound to 30S ribosomal subunits of E. coli. It is shown that this IF-3-induced aminoacyl-tRNA release cannot be attributed to either nucleolytic attack or competition between IF-3 and aminoacyl-tRNA for the same ribosomal binding site. It was found that the 30S-aminoacyl-tRNA-codon complexes formed in the absence of IF-3 are intrinsically different from those prepared in the presence of IF-3. In the absence of IF-3, the ribosomal binding of aminoacyl-tRNA is a virtually irreversible process, since the bound aminoacyl-tRNA can neither be spontaneously released upon dilution nor exchanged for unbound aminoacyl-tRNA. In the presence of IF-3, the binding of one molecule of IF-3 per 30S ribosome renders the binding of aminoacyl-tRNA reversible upon dilution and promotes exchange between bound and unbound aminoacyl-tRNA. It is suggested that this difference is due to a conformational transition of the 30S ribosomal subunit induced by the binding of IF-3. The possible implications of this finding in relation to the mechanism of action of IF-3 and its functional role in the cell are discussed.
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Paradies HH, Franz A, Pon CL, Gualerzi C. Conformational transition of the 30 S ribosomal subunit induced by initiation factor 3 (IF-3). Biochem Biophys Res Commun 1974; 59:600-7. [PMID: 4604265 DOI: 10.1016/s0006-291x(74)80022-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Gualerzi C, Wabl MR, Pon CL. Lack of stable initiation factor 3 (IF-3) binding to dimers of the 30 S ribosomal subunits. FEBS Lett 1973; 35:313-6. [PMID: 4582947 DOI: 10.1016/0014-5793(73)80312-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Gualerzi C, Pon CL. Nature of the ribosomal binding site for initiation factor 3 (IF-3). Biochem Biophys Res Commun 1973; 52:792-9. [PMID: 4575784 DOI: 10.1016/0006-291x(73)91007-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Pon CL, Friedman SM, Gualerzi C. Studies on the interaction between ribosomes and 14 CH 3 -F 3 initation factor. MOLECULAR & GENERAL GENETICS : MGG 1972; 116:192-8. [PMID: 4558194 DOI: 10.1007/bf00582228] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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