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Harne S, Gayathri P. Characterization of heterologously expressed Fibril, a shape and motility determining cytoskeletal protein of the helical bacterium Spiroplasma. iScience 2022; 25:105055. [PMID: 36157586 PMCID: PMC9489929 DOI: 10.1016/j.isci.2022.105055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/20/2022] [Accepted: 08/29/2022] [Indexed: 11/30/2022] Open
Abstract
Fibril is a constitutive filament-forming cytoskeletal protein of unidentified fold, exclusive to members of genus Spiroplasma. It is hypothesized to undergo conformational changes necessary to bring about Spiroplasma motility through changes in cell helicity. However, the mechanism driving conformational changes in Fibril remains unknown. We expressed Fibril from S. citri in E. coli for its purification and characterization. Sodium dodecyl sulfate solubilized Fibril filaments and facilitated purification by affinity chromatography. An alternative protocol for obtaining enriched insoluble Fibril filaments was standardized using density gradient centrifugation. Electron microscopy of Fibril purified by these protocols revealed filament bundles. Probable domain boundaries of Fibril protein were identified based on mass spectrometric analysis of proteolytic fragments. Presence of α-helical and β-sheet signatures in FT-IR measurements suggests that Fibril filaments consist of an assembly of folded globular domains, and not a β-strand-based aggregation like amyloid fibrils. Codon-optimized Spiroplasma citri Fibril was expressed in E. coli SDS treatment does not denature Fibril filaments Fibril possesses α helices and β sheet and is not an amyloid-like protein Domain boundaries were predicted using mass spectrometry of proteolytic fragments
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Affiliation(s)
- Shrikant Harne
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India
| | - Pananghat Gayathri
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India
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2
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Borges AL, Lou YC, Sachdeva R, Al-Shayeb B, Penev PI, Jaffe AL, Lei S, Santini JM, Banfield JF. Widespread stop-codon recoding in bacteriophages may regulate translation of lytic genes. Nat Microbiol 2022; 7:918-927. [PMID: 35618772 DOI: 10.1038/s41564-022-01128-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 04/21/2022] [Indexed: 11/09/2022]
Abstract
Bacteriophages (phages) are obligate parasites that use host bacterial translation machinery to produce viral proteins. However, some phages have alternative genetic codes with reassigned stop codons that are predicted to be incompatible with bacterial translation systems. We analysed 9,422 phage genomes and found that stop-codon recoding has evolved in diverse clades of phages that infect bacteria present in both human and animal gut microbiota. Recoded stop codons are particularly over-represented in phage structural and lysis genes. We propose that recoded stop codons might function to prevent premature production of late-stage proteins. Stop-codon recoding has evolved several times in closely related lineages, which suggests that adaptive recoding can occur over very short evolutionary timescales.
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Affiliation(s)
- Adair L Borges
- Innovative Genomics Institute, University of California, Berkeley, CA, USA.,Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
| | - Yue Clare Lou
- Innovative Genomics Institute, University of California, Berkeley, CA, USA.,Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Rohan Sachdeva
- Innovative Genomics Institute, University of California, Berkeley, CA, USA.,Earth and Planetary Science, University of California, Berkeley, CA, USA
| | - Basem Al-Shayeb
- Innovative Genomics Institute, University of California, Berkeley, CA, USA.,Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Petar I Penev
- Earth and Planetary Science, University of California, Berkeley, CA, USA
| | - Alexander L Jaffe
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Shufei Lei
- Earth and Planetary Science, University of California, Berkeley, CA, USA
| | - Joanne M Santini
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Jillian F Banfield
- Innovative Genomics Institute, University of California, Berkeley, CA, USA. .,Environmental Science, Policy and Management, University of California, Berkeley, CA, USA. .,Earth and Planetary Science, University of California, Berkeley, CA, USA. .,Lawrence Berkeley National Laboratory, Berkeley, CA, USA. .,The University of Melbourne, Parkville, Victoria, Australia.
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3
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Hao W, Gao Q, Wang J, Gu W, Wang W, Meng Q. SPE0313 located at cell membrane of Spiroplasma eriocheiris is required for adhesion and invasion Eriocheir sinensis hemocytes. JOURNAL OF FISH DISEASES 2019; 42:423-430. [PMID: 30659624 DOI: 10.1111/jfd.12953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 12/04/2018] [Accepted: 12/06/2018] [Indexed: 06/09/2023]
Affiliation(s)
- Wenjing Hao
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Qi Gao
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Jian Wang
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Wei Gu
- Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Marine Science and Engineering, Nanjing Normal University, Nanjing, China
- Co-Innovation Center for Marine Bio-Industry Technology of Jiangsu Province, Lianyungang, Jiangsu, China
| | - Wen Wang
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Qingguo Meng
- Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Marine Science and Engineering, Nanjing Normal University, Nanjing, China
- Co-Innovation Center for Marine Bio-Industry Technology of Jiangsu Province, Lianyungang, Jiangsu, China
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4
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Infection Function of Adhesin-Like Protein ALP609 from Spiroplasma melliferum CH-1. Curr Microbiol 2018; 75:701-708. [PMID: 29362879 DOI: 10.1007/s00284-018-1435-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Accepted: 01/05/2018] [Indexed: 10/18/2022]
Abstract
Spiroplasma melliferum is the causative agent of spiroplasmosis in honeybees. During infection, adhesion of spiroplasmas to the host cells through adhesion factors is a crucial step. In this study, we identified an adhesin-like protein (ALP609) in S. melliferum CH-1 and investigated its role in the infection. To determine whether ALP609 is an adhesion factor, we performed indirect immunofluorescence microscopy to visualize its adhesion properties. Subsequently, an infection model of S. melliferum CH-1 was established using primary midgut cells of Apis mellifera to examine the adhesion and invasion of spiroplasma using anti-ALP609 antibodies inhibition assays and competition assays with recombinant ALP609 in vitro. We found that anti-ALP609 antibodies could inhibit the adhesion and invasion of spiroplasma to the midgut cells of A. mellifera and reduce midgut cell invasion on increased exposure to recombinant ALP609. To the best of our knowledge, this is the first report identifying adhesion-related factors in S. melliferum. Our results suggested that ALP609 is an adhesin-like protein critical for invasion of S. melliferum CH-1 into midgut cells of A. mellifera.
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Simões J, Bezerra AR, Moura GR, Araújo H, Gut I, Bayes M, Santos MAS. The Fungus Candida albicans Tolerates Ambiguity at Multiple Codons. Front Microbiol 2016; 7:401. [PMID: 27065968 PMCID: PMC4814463 DOI: 10.3389/fmicb.2016.00401] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/14/2016] [Indexed: 12/31/2022] Open
Abstract
The ascomycete Candida albicans is a normal resident of the gastrointestinal tract of humans and other warm-blooded animals. It occurs in a broad range of body sites and has high capacity to survive and proliferate in adverse environments with drastic changes in oxygen, carbon dioxide, pH, osmolarity, nutrients, and temperature. Its biology is unique due to flexible reassignment of the leucine CUG codon to serine and synthesis of statistical proteins. Under standard growth conditions, CUG sites incorporate leucine (3% of the times) and serine (97% of the times) on a proteome wide scale, but leucine incorporation fluctuates in response to environmental stressors and can be artificially increased up to 98%. In order to determine whether such flexibility also exists at other codons, we have constructed several serine tRNAs that decode various non-cognate codons. Expression of these tRNAs had minor effects on fitness, but growth of the mistranslating strains at different temperatures, in medium with different pH and nutrients composition was often enhanced relatively to the wild type (WT) strain, supporting our previous data on adaptive roles of CUG ambiguity in variable growth conditions. Parallel evolution of the recombinant strains (100 generations) followed by full genome resequencing identified various strain specific single nucleotide polymorphisms (SNP) and one SNP in the deneddylase (JAB1) gene in all strains. Since JAB1 is a subunit of the COP9 signalosome complex, which interacts with cullin (Cdc53p) to mediate degradation of a variety of cellular proteins, our data suggest that neddylation plays a key role in tolerance and adaptation to codon ambiguity in C. albicans.
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Affiliation(s)
- João Simões
- Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro Aveiro, Portugal
| | - Ana R Bezerra
- Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro Aveiro, Portugal
| | - Gabriela R Moura
- Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro Aveiro, Portugal
| | - Hugo Araújo
- Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro Aveiro, Portugal
| | - Ivo Gut
- Centro Nacional de Análises Genómico, Parc Científic Barcelona, Spain
| | - Mónica Bayes
- Centro Nacional de Análises Genómico, Parc Científic Barcelona, Spain
| | - Manuel A S Santos
- Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro Aveiro, Portugal
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Bezerra AR, Guimarães AR, Santos MAS. Non-Standard Genetic Codes Define New Concepts for Protein Engineering. Life (Basel) 2015; 5:1610-28. [PMID: 26569314 PMCID: PMC4695839 DOI: 10.3390/life5041610] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 10/12/2015] [Accepted: 10/21/2015] [Indexed: 11/16/2022] Open
Abstract
The essential feature of the genetic code is the strict one-to-one correspondence between codons and amino acids. The canonical code consists of three stop codons and 61 sense codons that encode 20% of the amino acid repertoire observed in nature. It was originally designated as immutable and universal due to its conservation in most organisms, but sequencing of genes from the human mitochondrial genomes revealed deviations in codon assignments. Since then, alternative codes have been reported in both nuclear and mitochondrial genomes and genetic code engineering has become an important research field. Here, we review the most recent concepts arising from the study of natural non-standard genetic codes with special emphasis on codon re-assignment strategies that are relevant to engineering genetic code in the laboratory. Recent tools for synthetic biology and current attempts to engineer new codes for incorporation of non-standard amino acids are also reviewed in this article.
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Affiliation(s)
- Ana R Bezerra
- Health Sciences Department, Institute for Biomedicine-iBiMED, University of Aveiro, Campus de Santiago, Aveiro 3810-193, Portugal.
| | - Ana R Guimarães
- Health Sciences Department, Institute for Biomedicine-iBiMED, University of Aveiro, Campus de Santiago, Aveiro 3810-193, Portugal.
| | - Manuel A S Santos
- Health Sciences Department, Institute for Biomedicine-iBiMED, University of Aveiro, Campus de Santiago, Aveiro 3810-193, Portugal.
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Meng Q, Ou J, Ji H, Jiang X, Gu W, Wang W. Identification and characterization of spiralin-like protein SLP25 from Spiroplasma eriocheiris. Vet Microbiol 2010; 144:473-7. [DOI: 10.1016/j.vetmic.2010.01.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 01/12/2010] [Accepted: 01/14/2010] [Indexed: 10/19/2022]
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Meng Q, Gu W, Bi K, Ji H, Wang W. Spiralin-like protein SLP31 from Spiroplasma eriocheiris as a potential antigen for immunodiagnostics of tremor disease in Chinese mitten crab Eriocheir sinensis. Folia Microbiol (Praha) 2010; 55:245-50. [PMID: 20526837 DOI: 10.1007/s12223-010-0036-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 11/19/2009] [Indexed: 11/25/2022]
Abstract
Spiroplasma eriocheiris caused massive mortality of Chinese mitten crab Eriocheir sinensis but little is known about the molecular characteristics of this microorganism. We described here the identification of a spiralin-like protein (SLP31) from S. eriocheiris and expression in Escherichia coli. Analysis of the nucleotide sequence revealed that the clone has an open reading frame of 837 bp encoding a protein of 279 amino acids. Theoretical isoelectric point and molar mass for SLP31 are 7.72 and 31 kDa, respectively. The similarity of SLP31 deduced amino acid sequence shared with the spiralin from other species indicated that the gene may be a member of spiralin family. The TGA codon in Spiroplasma serves not as a stop signal but as a code for the amino acid tryptophan. After cloning the SLP31, the gene was site-mutated from TGA to TGG and transcribed in E. coli to full expression of SLP31. The purified recombinant protein was used to determine the immune reactivity by Western blotting which suggests that SLP31 could be a good antigen for immunodiagnostic of tremor disease in E. sinensis.
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Affiliation(s)
- Qingguo Meng
- Jiangsu Key Laboratory for Biodiversity & Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, 210046, China
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Marais A, Bové JM, Renaudin J. Spiroplasma citri virus SpV1-derived cloning vector: deletion formation by illegitimate and homologous recombination in a spiroplasmal host strain which probably lacks a functional recA gene. J Bacteriol 1996; 178:862-70. [PMID: 8550524 PMCID: PMC177736 DOI: 10.1128/jb.178.3.862-870.1996] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We have previously described the use of the replicative form (RF) of Spiroplasma citri virus SpV1 as a vector for expressing an epitope of the P1 adhesin protein from Mycoplasma pneumoniae in S. citri (A. Marais, J. M. Bové, S.F. Dallo, J. B. Baseman, and J. Renaudin, J. Bacteriol. 175:2783-2787, 1993). We have now studied the structural instability of the recombinant RF leading to loss of the DNA insert. Analyses of viral clones with deletions have shown that both illegitimate and homologous recombination were involved in deletion formation. For one such clone, deletion has occurred via a double crossing-over exchange between the circular free viral RF and SpV1 viral sequences present in the S. citri host chromosome. The homologous recombination process usually requires the RecA protein. However, characterization of the recA gene of the S. citri R8A2 host strain revealed that over two-thirds of the open reading frame of the recA gene was deleted from the C-terminal part, indicating that this particular strain is probably RecA deficient.
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Affiliation(s)
- A Marais
- Laboratoire de Biologie Cellulaire et Moléculaire Institut National de la Recherche Agronomique, Domaine de la Grande Ferrade, Villenave d'Omon, France
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Renaudin J, Marais A, Verdin E, Duret S, Foissac X, Laigret F, Bové JM. Integrative and free Spiroplasma citri oriC plasmids: expression of the Spiroplasma phoeniceum spiralin in Spiroplasma citri. J Bacteriol 1995; 177:2870-7. [PMID: 7751299 PMCID: PMC176961 DOI: 10.1128/jb.177.10.2870-2877.1995] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The replication region (oriC) of the Spiroplasma citri chromosome has been recently sequenced, and a 2-kbp DNA fragment was characterized as an autonomously replicating sequence (F. Ye, J. Renaudin, J. M. Bové, and F. Laigret, Curr. Microbiol. 29:23-29, 1994). In the present studies, we have combined this DNA fragment, containing the dnaA gene and the flanking dnaA boxes, with a ColE1-derived Escherichia coli replicon and the Tet M determinant, which confers resistance to tetracycline. The recombinant plasmid, named pBOT1, was introduced into S. citri cells, in which it replicated. Plasmid pBOT1 was shuttled from E. coli to S. citri and back to E. coli. In S. citri, replication of pBOT1 did not require the presence of a functional dnaA gene on the plasmid. However, the dnaA box region downstream of the dnaA gene was essential. Upon passaging of the S. citri transformants, the plasmid integrated into the spiroplasmal host chromosome by recombination at the replication origin. The integration process led to duplication of the oriC sequences. In contrast to the integrative pBOT1, plasmid pOT1, which does not contain the E. coli replicon, was stably maintained as a free extrachromosomal element. Plasmid pOT1 was used as a vector to introduce into S. citri the G fragment of the cytadhesin P1 gene of Mycoplasma pneumoniae and the spiralin gene of Spiroplasma phoeniceum. The recombinant plasmids, pOTPG with the G fragment and pOTPS with the spiralin gene, were stably maintained in spiroplasmal transformants. Expression of the heterologous S. phoeniceum spiralin in S. citri was demonstrated by Western immunoblotting.
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Affiliation(s)
- J Renaudin
- Laboratoire de Biologie Cellulaire et Moléculaire, Institut National de la Recherche Agronomique, Villenave d'Ornon, France
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Ye F, Renaudin J, Bové JM, Laigret F. Cloning and sequencing of the replication origin (oriC) of the Spiroplasma citri chromosome and construction of autonomously replicating artificial plasmids. Curr Microbiol 1994; 29:23-9. [PMID: 7764984 DOI: 10.1007/bf01570187] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A 5.6-kbp fragment of Spiroplasma citri DNA containing the dnaA gene has been cloned and sequenced. Nucleotide sequence analysis shows that this fragment harbors the genes for the replication initiator protein (dnaA), the beta subunit of DNA polymerase III (dnaN), and the DNA gyrase subunits A and B (gyrA and gyrB). The arrangement of these genes, dnaA-dnaN-gyrB-gyrA, is similar to that found in all Gram-positive bacterial genomes studied so far, except that no recF gene was found between dnaN and gyrB. Several DnaA-box consensus sequences were found upstream of dnaA and in the dnaA-dnaN intergenic region. The dnaA region with the flanking DnaA-boxes and the tetracycline resistance determinant, tetM, were linked into a circular recombinant DNA. This DNA was able to replicate autonomously when introduced by electroporation into S. citri cells. These experiments show that the dnaA region with the DnaA-boxes is the origin of replication of S. citri and can be used to construct gene vectors.
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Affiliation(s)
- F Ye
- Laboratory of Cellular and Molecular Biology, National Institute of Agronomy Research, Villenave d'Ornon, France
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Renaudin J, Bové JM. SpV1 and SpV4, spiroplasma viruses with circular, single-stranded DNA genomes, and their contribution to the molecular biology of spiroplasmas. Adv Virus Res 1994; 44:429-463. [PMID: 7817879 DOI: 10.1016/s0065-3527(08)60335-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Renaudin
- Laboratoire de Biologie Cellulaire et Moléculaire, INRA et Université de Bordeaux II, Villenave d'Ornon, France
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Marais A, Bove JM, Dallo SF, Baseman JB, Renaudin J. Expression in Spiroplasma citri of an epitope carried on the G fragment of the cytadhesin P1 gene from Mycoplasma pneumoniae. J Bacteriol 1993; 175:2783-7. [PMID: 7683022 PMCID: PMC204586 DOI: 10.1128/jb.175.9.2783-2787.1993] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have previously described the use of the replicative form (RF) of Spiroplasma citri virus SpV1 as a vector for cloning and expressing foreign genes in S. citri, an organism which reads UGA as a tryptophan codon (C. Stamburski, J. Renaudin, and J.M. Bové, J. Bacteriol. 173:2225-2230, 1991). We now report cloning and expression in S. citri of the G fragment of cytadhesin P1 gene from Mycoplasma pneumoniae. The G fragment was inserted in the SpV1 RF downstream of a synthetic ribosome binding site and introduced into S. citri by electroporation. Northern (RNA) blot analyses showed that in S. citri, the G fragment was transcribed from an SpV1 RF promoter as a 1.2-kb mRNA. The translation product was detected by Western blotting (immunoblotting) with a rabbit antiserum raised against total proteins from M. pneumoniae (strain FH) and was proved to be P1 specific by using monoclonal antibodies specific for the G region of the P1 protein. The apparent molecular mass of the polypeptide (24.5 kDa) indicates that in S. citri, the G fragment was fully translated in spite of the seven UGA codons present in the reading frame.
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Affiliation(s)
- A Marais
- Laboratoire de Biologie Cellulaire et Moléculaire, Institut National de la Recherche Agronomique, Villenave d'Ornon, France
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Citti C, Maréchal-Drouard L, Saillard C, Weil JH, Bové JM. Spiroplasma citri UGG and UGA tryptophan codons: sequence of the two tryptophanyl-tRNAs and organization of the corresponding genes. J Bacteriol 1992; 174:6471-8. [PMID: 1383193 PMCID: PMC207606 DOI: 10.1128/jb.174.20.6471-6478.1992] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
From the total tRNAs of Spiroplasma citri, we isolated and purified two tRNA(Trp) species by using chromatography on an RPC-5 column followed by denaturing polyacrylamide gel electrophoresis. The sequence of the two tRNAs, as well as the sequences of the corresponding genes, were determined. One of the two tRNA(Trp) species has a CCA anticodon and is able to pair with the universal UGG tryptophan codon, while the second has a U*CA (U* is a modified uridine) anticodon and is able to pair with UGA but also with UGG in accordance with the "U:N wobble" rule. Thus, in S. citri, UGA is not a stop codon but codes for tryptophan. The two tRNA(Trp) genes, together with a third tRNA gene, tRNA(Ser) (CGA), belong to a single transcription unit. The nucleotide sequences of the two tRNA(Trp) species show 82.9% similarity. The two spiroplasmal tRNA(Trp) species can be aminoacylated by using an aminoacyl-tRNA synthetase fraction from S. citri. In contrast, the enzyme fraction from Escherichia coli aminoacylates tRNA(Trp) (CCA) but not tRNA(Trp) (U*CA).
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Affiliation(s)
- C Citti
- Laboratoire de Biologie Cellulaire et Moléculaire, Institut National de la Recherche Agronomique, Villenave d'Ornon, France
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