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Ziehe D, Dünschede B, Zenker M, Funke S, Nowaczyk MM, Schünemann D. The Chloroplast SRP Systems of Chaetosphaeridium globosum and Physcomitrella patens as Intermediates in the Evolution of SRP-Dependent Protein Transport in Higher Plants. PLoS One 2016; 11:e0166818. [PMID: 27861610 PMCID: PMC5115805 DOI: 10.1371/journal.pone.0166818] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 11/05/2016] [Indexed: 11/19/2022] Open
Abstract
The bacterial signal recognition particle (SRP) mediates the cotranslational targeting of membrane proteins and is a high affinity complex consisting of a SRP54 protein subunit (Ffh) and an SRP RNA. The chloroplast SRP (cpSRP) pathway has adapted throughout evolution to enable the posttranslational targeting of the light harvesting chlorophyll a/b binding proteins (LHCPs) to the thylakoid membrane. In spermatophytes (seed plants), the cpSRP lacks the SRP RNA and is instead formed by a high affinity interaction of the conserved 54-kD subunit (cpSRP54) with the chloroplast-specific cpSRP43 protein. This heterodimeric cpSRP recognizes LHCP and delivers it to the thylakoid membrane. However, in contrast to spermatophytes, plastid SRP RNAs were identified within all streptophyte lineages and in all chlorophyte branches. Furthermore, it was shown that cpSRP43 does not interact with cpSRP54 in chlorophytes (e.g., Chlamydomonas reinhardtii). In this study, we biochemically characterized the cpSRP system of the charophyte Chaetosphaeridium globosum and the bryophyte Physcomitrella patens. Interaction studies demonstrate low affinity binding of cpSRP54 to cpSRP43 (Kd ~10 μM) in Chaetosphaeridium globosum and Physcomitrella patens as well as relatively low affinity binding of cpSRP54 to cpSRP RNA (Kd ~1 μM) in Physcomitrella patens. CpSRP54/cpSRP43 complex formation in charophytes is supported by the finding that specific alterations in the second chromodomain of cpSRP43, that are conserved within charophytes and absent in land plants, do not interfere with cpSRP54 binding. Furthermore, our data show that the elongated apical loop structure of the Physcomitrella patens cpSRP RNA contributes to the low binding affinity between cpSRP54 and the cpSRP RNA.
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Affiliation(s)
- Dominik Ziehe
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Beatrix Dünschede
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Mira Zenker
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Silke Funke
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Marc M. Nowaczyk
- Cyanobacterial Membrane Protein Complexes, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Danja Schünemann
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780, Bochum, Germany
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2
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Clabbers MTB, Olsthoorn RCL, Gultyaev AP. Tospovirus ambisense genomic RNA segments use almost complete repertoire of stable tetraloops in the intergenic region. ACTA ACUST UNITED AC 2014; 30:1800-4. [PMID: 24590440 DOI: 10.1093/bioinformatics/btu122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The intergenic regions of the ambisense RNA segments of viruses from the Tospovirus genus form large extended RNA structures that regulate virus replication. Using comparative structure analysis, we show the presence of conserved alternative conformations at the apical parts of these structures. In one conformation, a branched Y-shape, the 5'-proximal hairpin arms are mostly capped by exceptionally stable tetraloop motifs. The tetraloop hairpins are folded in both virus and virus-complementary sense RNAs, and different tetraloops can functionally replace each other. Folding simulations show that the branched Y-shape structures can undergo a conformational transition to alternative extended rod-like conformations. Functional importance of both alternatives is supported by nucleotide covariations. The balanced equilibrium between alternative structures is evidenced by native gel electrophoresis of mutant RNA transcripts with shifted equilibria. The tetraloops play a role in the stability and dynamics of structures but may also be recognized by proteins involved in translation and/or replication.
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Affiliation(s)
- Max T B Clabbers
- Institute of Chemistry, Leiden University, 2300 RA Leiden and Department of Viroscience, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Rene C L Olsthoorn
- Institute of Chemistry, Leiden University, 2300 RA Leiden and Department of Viroscience, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Alexander P Gultyaev
- Institute of Chemistry, Leiden University, 2300 RA Leiden and Department of Viroscience, Erasmus Medical Center, 3000 CA Rotterdam, The NetherlandsInstitute of Chemistry, Leiden University, 2300 RA Leiden and Department of Viroscience, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands
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3
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Kührová P, Banáš P, Best RB, Šponer J, Otyepka M. Computer Folding of RNA Tetraloops? Are We There Yet? J Chem Theory Comput 2013; 9:2115-25. [DOI: 10.1021/ct301086z] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Petra Kührová
- Regional Centre of Advanced Technologies
and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Pavel Banáš
- Regional Centre of Advanced Technologies
and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic
- Institute
of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska
135, 612 65 Brno, Czech Republic
| | - Robert B. Best
- Laboratory of Chemical Physics,
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520,
United States
| | - Jiří Šponer
- Institute
of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska
135, 612 65 Brno, Czech Republic
- CEITEC − Central European
Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies
and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic
- Institute
of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska
135, 612 65 Brno, Czech Republic
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4
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Sahu B, Khade PK, Joseph S. Functional replacement of two highly conserved tetraloops in the bacterial ribosome. Biochemistry 2012; 51:7618-26. [PMID: 22938718 DOI: 10.1021/bi300930r] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ribosomes are RNA-protein complexes responsible for protein synthesis. A dominant structural motif in the rRNAs is an RNA helix capped with a four-nucleotide loop, called a tetraloop. The sequence of the tetraloop is invariant at some positions in the rRNAs but is highly variable at other positions. The biological reason for the conservation of the tetraloop sequence at specific positions in the rRNAs is not clear. In the 16S rRNA, the GAAA tetraloop in helix 8 and the UACG tetraloop in helix 14 are highly conserved and located near the binding site for EF-Tu and EF-G. To investigate whether the structural stability of the tetraloop or the precise sequence of the tetraloop is important for function, we separately changed the GAAA tetraloop in helix 8 to a UACG tetraloop and the UACG tetraloop in helix 14 to a GAAA tetraloop. The effects of the tetraloop replacements on protein synthesis were analyzed in vivo and in vitro. Replacement of the tetraloops in helices 8 and 14 did not significantly affect the growth rate of the Escherichia coli (Δ7rrn) strain. However, the mutant ribosomes showed a slightly reduced rate of protein synthesis in vitro. In addition, we observed a 2-fold increase in the error rate of translation with the mutant ribosomes, which is consistent with an earlier report. Our results suggest that the tetraloops in helices 8 and 14 are highly conserved mainly for their structural stability and the precise sequences of these tetraloops are not critical for protein synthesis.
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Affiliation(s)
- Bhubanananda Sahu
- Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0314, USA
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5
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Mohan S, Hsiao C, Bowman JC, Wartell R, Williams LD. RNA Tetraloop Folding Reveals Tension between Backbone Restraints and Molecular Interactions. J Am Chem Soc 2010; 132:12679-89. [DOI: 10.1021/ja104387k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Srividya Mohan
- School of Chemistry and Biochemistry, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Chiaolong Hsiao
- School of Chemistry and Biochemistry, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Jessica C. Bowman
- School of Chemistry and Biochemistry, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Roger Wartell
- School of Chemistry and Biochemistry, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Loren Dean Williams
- School of Chemistry and Biochemistry, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
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6
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Hsiao C, Mohan S, Kalahar BK, Williams LD. Peeling the onion: ribosomes are ancient molecular fossils. Mol Biol Evol 2009; 26:2415-25. [PMID: 19628620 DOI: 10.1093/molbev/msp163] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We describe a method to establish chronologies of ancient ribosomal evolution. The method uses structure-based and sequence-based comparison of the large subunits (LSUs) of Haloarcula marismortui and Thermus thermophilus. These are the highest resolution ribosome structures available and represent disparate regions of the evolutionary tree. We have sectioned the superimposed LSUs into concentric shells, like an onion, using the site of peptidyl transfer as the origin (the PT-origin). This spherical approximation combined with a shell-by-shell comparison captures significant information along the evolutionary time line revealing, for example, that sequence and conformational similarity of the 23S rRNAs are greatest near the PT-origin and diverge smoothly with distance from it. The results suggest that the conformation and interactions of both RNA and protein can be described as changing, in an observable manner, over evolutionary time. The tendency of macromolecules to assume regular secondary structural elements such as A-form helices with Watson-Crick base pairs (RNA) and alpha-helices and beta-sheets (protein) is low at early time points but increases as time progresses. The conformations of ribosomal protein components near the PT-origin suggest that they may be molecular fossils of the peptide ancestors of ribosomal proteins. Their abbreviated length may have proscribed formation of secondary structure, which is indeed nearly absent from the region of the LSU nearest the PT-origin. Formation and evolution of the early PT center may have involved Mg(2+)-mediated assembly of at least partially single-stranded RNA oligomers or polymers. As one moves from center to periphery, proteins appear to replace magnesium ions. The LSU is known to have undergone large-scale conformation changes upon assembly. The T. thermophilus LSU analyzed here is part of a fully assembled ribosome, whereas the H. marismortui LSU analyzed here is dissociated from other ribosomal components. Large-scale conformational differences in the 23S rRNAs are evident from superimposition and prevent structural alignment of some portions of the rRNAs, including the L1 stalk.
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Affiliation(s)
- Chiaolong Hsiao
- School of Chemistry and Biochemistry, Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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7
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Abstract
New structural analysis methods, and a tree formalism re-define and expand the RNA motif concept, unifying what previously appeared to be disparate groups of structures. We find RNA tetraloops at high frequencies, in new contexts, with unexpected lengths, and in novel topologies. The results, with broad implications for RNA structure in general, show that even at this most elementary level of organization, RNA tolerates astounding variation in conformation, length, sequence and context. However the variation is not random; it is well-described by four distinct modes, which are 3-2 switches (backbone topology variations), insertions, deletions and strand clips.
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Affiliation(s)
| | | | - Eli Hershkovitz
- Departments of Electrical and Computer Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
- Department of Biomedical Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
| | - Allen Tannenbaum
- Departments of Electrical and Computer Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
- Department of Biomedical Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
| | - Loren Dean Williams
- To whom correspondence should be addressed. Tel: +1 404 894 9752; Fax: +1 404 894 7452;
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8
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Grajcar L, El Amri C, Ghomi M, Fermandjian S, Huteau V, Mandel R, Lecomte S, Baron MH. Assessment of adenyl residue reactivity within model nucleic acids by surface enhanced Raman spectroscopy. Biopolymers 2006; 82:6-28. [PMID: 16425174 DOI: 10.1002/bip.20455] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We rank the reactivity of the adenyl residues (A) of model DNA and RNA molecules with electropositive subnano size [Ag]n+ sites as a function of nucleic acid primary sequences and secondary structures and in the presence of biological amounts of Cl- and Na+ or Mg2+ ions. In these conditions A is markedly more reactive than any other nucleic acid bases. A reactivity is higher in ribo (r) than in deoxyribo (d) species [pA>pdA and (pA)n>>(pdA)n]. Base pairing decreases A reactivity in corresponding duplexes but much less in r than in d. In linear single and paired dCAG or dGAC loci, base stacking inhibits A reactivity even if A is bulged or mispaired (A.A). dA tracts are highly reactive only when dilution prevents self-association and duplex structures. In d hairpins the solvent-exposed A residues are reactive in CAG and GAC triloops and even more in ATC loops. Among the eight rG1N2R3A4 loops, those bearing a single A (A4) are the least reactive. The solvent-exposed A2 is reactive, but synergistic structural transitions make the initially stacked A residues of any rGNAA loop much more reactive. Mg2+ cross-bridging single strands via phosphates may screen A reactivity. In contrast d duplexes cross-bridging enables "A flipping" much more in rA.U pairs than in dA.T. Mg2+ promotes A reactivity in unpaired strands. For hairpins Mg2+ binding stabilizes the stems, but according to A position in the loops, A reactivity may be abolished, reduced, or enhanced. It is emphasized that not only accessibility but also local flexibility, concerted docking, and cation and anion binding control A reactivity.
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Affiliation(s)
- Lydie Grajcar
- Laboratoire de Dynamique Interactions et Réactivité, UMR 7075, Université Paris 6 CNRS, 2 rue Henri Dunant, 94320, Thiais, France
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9
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Fernández-Miragall O, Martínez-Salas E. Structural organization of a viral IRES depends on the integrity of the GNRA motif. RNA (NEW YORK, N.Y.) 2003; 9:1333-44. [PMID: 14561883 PMCID: PMC1287055 DOI: 10.1261/rna.5950603] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Little is known about the tertiary structure of internal ribosome entry site (IRES) elements. The central domain of foot-and-mouth disease (FMDV) IRES, named 3 or I, contains a conserved GNRA motif, essential for IRES activity. We have combined functional analysis with RNA probing to define its structural organization. We have found that a UNCG motif does not functionally substitute the GNRA motif; moreover, binding of synthetic GNRA stem-loops to domain 3 was significantly reduced in RNAs bearing UCCG or GUAG substitutions. The apical region of domain 3 consists of a four-way junction where residues of the GNRA tetraloop are responsible for the organization of the adjacent stem-loops, as deduced from ribonucleases and dimethyl sulfate accessibility. A single A-to-G substitution in the fourth position of this motif led to a strong RNA reorganization, affecting several nucleotides away in the secondary structure of domain 3. The study of mutants bearing UNCG or GUAG tetraloops revealed lack of protection to chemical attack in native RNA at specific nucleotides relative to the parental GUAA, suggesting that the GNRA motif dictates the organization and stability of domain 3. This effect is likely mediated by the interaction with distant residues. Therefore, the GNRA motif plays a crucial role in the organization of IRES structure with important consequences on activity.
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Affiliation(s)
- Olga Fernández-Miragall
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas--Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain
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10
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De la Peña M, Flores R. Chrysanthemum chlorotic mottle viroid RNA: dissection of the pathogenicity determinant and comparative fitness of symptomatic and non-symptomatic variants. J Mol Biol 2002; 321:411-21. [PMID: 12162955 DOI: 10.1016/s0022-2836(02)00629-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Chrysanthemum chlorotic mottle viroid (CChMVd) is a small RNA (398-401nt) with hammerhead ribozymes in both polarity strands that mediate self-cleavage of the oligomeric RNA intermediates generated in a rolling-circle mechanism of replication. Within the in vivo branched RNA conformation of CChMVd, a tetraloop has been identified as a major determinant of pathogenicity. Here we present a detailed study of this tetraloop by site-directed mutagenesis, bioassay of the CChMV-cDNA clones and analysis of the resulting progenies. None of the changes introduced in the tetraloop, including its substitution by a triloop or a pentaloop, abolished infectivity. In contrast to observations for other RNAs, the thermodynamically stable GAAA tetraloop characteristic of non-symptomatic CChMVd-NS strains was not functionally interchangeable for other stable tetraloops of the UNCG family, suggesting that the sequence, rather than the structure, is the major factor governing conservation of this motif. In most cases, the changes introduced initially led to symptomless infections, which eventually evolved to be symptomatic concurrently with the prevalence in the progeny of the UUUC tetraloop characteristic of symptomatic CChMVd-S strains. Only in one case did the GAAA tetraloop emerge and eventually dominate the progeny in infected plants that were non-symptomatic. These results revealed two major fitness peaks in the tetraloop (UUUC and GAAA), whose adjacent stem was also under strong selection pressure. Co-inoculations with CChMVd-S and -NS variants showed that only when the latter was in a 100- or 1000-fold excess did the infected plants remain symptomless, confirming the higher biological fitness of the S variant and explaining the lack of symptom expression previously observed in cross-protection experiments.
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Affiliation(s)
- Marcos De la Peña
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Avenida de los Naranjos s/n, Universidad Politécnica de Valencia, 46022, Valencia, Spain
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11
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Bélanger F, Léger M, Saraiya AA, Cunningham PR, Brakier-Gingras L. Functional studies of the 900 tetraloop capping helix 27 of 16S ribosomal RNA. J Mol Biol 2002; 320:979-89. [PMID: 12126619 DOI: 10.1016/s0022-2836(02)00550-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 900 tetraloop (positions 898-901) of Escherichia coli 16S rRNA caps helix 27, which is involved in a conformational switch crucial for the decoding function of the ribosome. This tetraloop forms a GNRA motif involved in intramolecular RNA-RNA interactions with its receptor in helix 24 of 16S rRNA. It is involved also in an intersubunit bridge, via an interaction with helix 67 in domain IV of 23S rRNA. Using a specialized ribosome system and an instant-evolution procedure, the four nucleotides of this loop were randomized and 15 functional mutants were selected in vivo. Positions 899 and 900, responsible for most of the tetraloop/receptor interactions, were found to be the most critical for ribosome activity. Functional studies showed that mutations in the 900 tetraloop impair subunit association and decrease translational fidelity. Computer modeling of the mutations allows correlation of the effect of mutations with perturbations of the tetraloop/receptor interactions.
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Affiliation(s)
- François Bélanger
- Département de Biochimie, Université de Montréal, Montréal, Québec, Canada
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12
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Jagath JR, Matassova NB, de Leeuw E, Warnecke JM, Lentzen G, Rodnina MV, Luirink J, Wintermeyer W. Important role of the tetraloop region of 4.5S RNA in SRP binding to its receptor FtsY. RNA (NEW YORK, N.Y.) 2001; 7:293-301. [PMID: 11233986 PMCID: PMC1370087 DOI: 10.1017/s1355838201002205] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Binding of Escherichia coli signal recognition particle (SRP) to its receptor, FtsY, requires the presence of 4.5S RNA, although FtsY alone does not interact with 4.5S RNA. In this study, we report that the exchange of the GGAA tetraloop sequence in domain IV of 4.5S RNA for UUCG abolishes SRP-FtsY interaction, as determined by gel retardation and membrane targeting experiments, whereas replacements with other GNRA-type tetraloops have no effect. A number of other base exchanges in the tetraloop sequence have minor or intermediate inhibitory effects. Base pair disruptions in the stem adjacent to the tetraloop or replacement of the closing C-G base pair with G-C partially restored function of the otherwise inactive UUCG mutant. Chemical probing by hydroxyl radical cleavage of 4.5S RNA variants show that replacing GGAA with UUCG in the tetraloop sequence leads to structural changes both within the tetraloop and in the adjacent stem; the latter change is reversed upon reverting the C-G closing base pair to G-C. These results show that the SRP-FtsY interaction is strongly influenced by the structure of the tetraloop region of SRP RNA, in particular the tetraloop stem, and suggest that both SRP RNA and Ffh undergo mutual structural adaptation to form SRP that is functional in the interaction with the receptor, FtsY.
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Affiliation(s)
- J R Jagath
- Institute of Molecular Biology, University of Witten/Herdecke, Witten, Germany
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13
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Williams DJ, Hall KB. Experimental and theoretical studies of the effects of deoxyribose substitutions on the stability of the UUCG tetraloop. J Mol Biol 2000; 297:251-65. [PMID: 10704320 DOI: 10.1006/jmbi.2000.3547] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Experimental and theoretical thermodynamic studies of the consequences of 2'-hydroxyl substitution in the RNA UUCG tetraloop show distinct position dependence consistent with the diverse structural contexts of the four-loop ribose hydroxyls in this motif. The results suggest that even for simple substitutions, such as the replacement of the ribose hydroxyl (2'-OH) with hydrogen (2'-H), the free energy change reflects a complex interplay of hydrogen bonding and solvation effects and is influenced by the intrinsic pucker preferences of the nucleotides. Furthermore, theoretical studies suggest that the effect of these mutations in the single-strand state is sequence dependent, in contrast to what is commonly assumed. Free energy perturbation simulations of ribose-deoxyribose mutations in a single-strand dodecamer and in trinucleotide models suggest that in the denatured state, the magnitude of the free energy change for deoxyribose substitutions is determined to a larger extent by the identity of the nucleotide (A, C, G or U) rather than its structural context. Single-strand mutational effects must be considered when interpreting mutational studies in molecular terms.
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Affiliation(s)
- D J Williams
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, USA
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14
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Rincón-Guzmán A, Beltrán-Peña E, Ortíz-López A, Sánchez de Jiménez E. Ribonucleoprotein particles of quiescent maize embryonic axes. PLANT MOLECULAR BIOLOGY 1998; 38:357-364. [PMID: 9747844 DOI: 10.1023/a:1006020121351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs) in many different tissues, particularly at some stages of metabolic quiescence. In this research RNPs from embryonic axes of mature maize seeds were isolated by sucrose and CsCl gradient centrifugation and characterized based on their RNA and protein contents. Two types of RNP particles of non-ribosomal nature were identified by northern blot analysis with specific probes: the 7S RNP and the signal recognition particle (SRP) particles which contain 5S rRNA and 7S RNA respectively. The proteins associated to these RNA molecules were the transcription factor TFIIIA-homologous protein associated to 7S RNP, and the p72, p68 and p54-GTPase proteins associated to SRP.
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Affiliation(s)
- A Rincón-Guzmán
- Departamento de Bioquímica, Conjunto E, Facultad de Química, Universidad Nacional Autónoma de México, México, DF
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15
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16
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Riedel L, Pütz A, Hauser MT, Luckinger R, Wassenegger M, Sänger HL. Characterization of the signal recognition particle (SRP) RNA population of tomato (Lycopersicon esculentum). PLANT MOLECULAR BIOLOGY 1995; 27:669-680. [PMID: 7727745 DOI: 10.1007/bf00020221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Molecular cloning of 30 cDNAs and subsequent characterization of the corresponding SRP RNA from four cultivars of tomato (Lycopersicon esculentum) revealed altogether 14 sequence variants, which could be ordered into six groups. The expression of five representatives from these groups was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) in different cultivars and different tissues. Although one cultivar-specific SRP RNA variant could be detected in the leaf SRP RNA population, identical SRP RNA populations seem to be present in the four different cultivars as well as in different tissues, such as leaves, flowers, fruits, stems and roots. Sequence comparison revealed that several variants might have evolved by recombination of two different SRP RNA sequences. On the basis of five SRP RNA variants, the current secondary structure model was refined and a new conserved structural element was detected. Comparative sequence analysis of domain II from all known SRP RNA homologues reveals a remarkable conservation of this element. As demonstrated previously, the corresponding area overlaps with a region that interact with the SRPp68/p72 heterodimer and/or with ribosomes. Based on structural and functional considerations, we propose that the domain IV structure together with the highly conserved area of domain II constitutes the essential core of the SRP RNA.
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Affiliation(s)
- L Riedel
- Max-Planck-Institut für Biochemie, Abteilung Viroidforschung, Martinsried, Germany
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17
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Selinger D, Brennwald P, Althoff S, Reich C, Hann B, Walter P, Wise JA. Genetic and biochemical analysis of the fission yeast ribonucleoprotein particle containing a homolog of Srp54p. Nucleic Acids Res 1994; 22:2557-67. [PMID: 8041618 PMCID: PMC308210 DOI: 10.1093/nar/22.13.2557] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Mammalian signal recognition particle (SRP), a complex of six polypeptides and one 7SL RNA molecule, is required for targeting nascent presecretory proteins to the endoplasmic reticulum (ER). Earlier work identified a Schizosaccharomyces pombe homolog of human SRP RNA and showed that it is a component of a particle similar in size and biochemical properties to mammalian SRP. The recent cloning of the gene encoding a fission yeast protein homologous to Srp54p has made possible further characterization of the subunit structure, subcellular distribution, and assembly of fission yeast SRP. S. pombe SRP RNA and Srp54p co-sediment on a sucrose velocity gradient and coimmunoprecipitate, indicating that they reside in the same complex. In vitro assays demonstrate that fission yeast Srp54p binds under stringent conditions to E. coli SRP RNA, which consists essentially of domain IV, but not to the full-length cognate RNA nor to an RNA in which domain III has been deleted in an effort to mirror the structure of bacterial homologs. Moreover, the association of S. pombe Srp54p with SRP RNA in vivo is disrupted by conditional mutations not only in domain IV, which contains its binding site, but in domains I and III, suggesting that the particle may assemble cooperatively. The growth defects conferred by mutations throughout SRP RNA can be suppressed by overexpression of Srp54p, and the degree to which growth is restored correlates inversely with the severity of the reduction in protein binding. Conditional mutations in SRP RNA also reduce its sedimentation with the ribosome/membrane pellet during cell fractionation. Finally, immunoprecipitation under native conditions of an SRP-enriched fraction from [35S]-labeled fission yeast cells suggests that five additional polypeptides are complexed with Srp54p; each of these proteins is similar in size to a constituent of mammalian SRP, implying that the subunit structure of this ribonucleoprotein is conserved over vast evolutionary distances.
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Affiliation(s)
- D Selinger
- Department of Biochemistry, University of Illinois at Urbana-Champaign 61801
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Althoff S, Selinger D, Wise JA. Molecular evolution of SRP cycle components: functional implications. Nucleic Acids Res 1994; 22:1933-47. [PMID: 7518075 PMCID: PMC308104 DOI: 10.1093/nar/22.11.1933] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Signal recognition particle (SRP) is a cytoplasmic ribonucleoprotein that targets a subset of nascent presecretory proteins to the endoplasmic reticulum membrane. We have considered the SRP cycle from the perspective of molecular evolution, using recently determined sequences of genes or cDNAs encoding homologs of SRP (7SL) RNA, the Srp54 protein (Srp54p), and the alpha subunit of the SRP receptor (SR alpha) from a broad spectrum of organisms, together with the remaining five polypeptides of mammalian SRP. Our analysis provides insight into the significance of structural variation in SRP RNA and identifies novel conserved motifs in protein components of this pathway. The lack of congruence between an established phylogenetic tree and size variation in 7SL homologs implies the occurrence of several independent events that eliminated more than half the sequence content of this RNA during bacterial evolution. The apparently non-essential structures are domain I, a tRNA-like element that is constant in archaea, varies in size among eucaryotes, and is generally missing in bacteria, and domain III, a tightly base-paired hairpin that is present in all eucaryotic and archeal SRP RNAs but is invariably absent in bacteria. Based on both structural and functional considerations, we propose that the conserved core of SRP consists minimally of the 54 kDa signal sequence-binding protein complexed with the loosely base-paired domain IV helix of SRP RNA, and is also likely to contain a homolog of the Srp68 protein. Comparative sequence analysis of the methionine-rich M domains from a diverse array of Srp54p homologs reveals an extended region of amino acid identity that resembles a recently identified RNA recognition motif. Multiple sequence alignment of the G domains of Srp54p and SR alpha homologs indicates that these two polypeptides exhibit significant similarity even outside the four GTPase consensus motifs, including a block of nine contiguous amino acids in a location analogous to the binding site of the guanine nucleotide dissociation stimulator (GDS) for E. coli EF-Tu. The conservation of this sequence, in combination with the results of earlier genetic and biochemical studies of the SRP cycle, leads us to hypothesize that a component of the Srp68/72p heterodimer serves as the GDS for both Srp54p and SR alpha. Using an iterative alignment procedure, we demonstrate similarity between Srp68p and sequence motifs conserved among GDS proteins for small Ras-related GTPases. The conservation of SRP cycle components in organisms from all three major branches of the phylogenetic tree suggests that this pathway for protein export is of ancient evolutionary origin.
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Affiliation(s)
- S Althoff
- University of Illinois, Department of Biochemistry, Urbana 61801
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