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Jain V, Kikuchi H, Oshima Y, Sharma A, Yogavel M. Structural and functional analysis of the anti-malarial drug target prolyl-tRNA synthetase. ACTA ACUST UNITED AC 2014; 15:181-90. [PMID: 25047712 DOI: 10.1007/s10969-014-9186-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 07/04/2014] [Indexed: 12/21/2022]
Abstract
Aminoacyl-tRNA synthetases (aaRSs) drive protein translation in cells and hence these are essential enzymes across life. Inhibition of these enzymes can halt growth of an organism by stalling protein translation. Therefore, small molecule targeting of aaRS active sites is an attractive avenue from the perspective of developing anti-infectives. Febrifugine and its derivatives like halofuginone (HF) are known to inhibit prolyl-tRNA synthetase of malaria parasite Plasmodium falciparum. Here, we present functional and crystallographic data on P. falciparum prolyl-tRNA synthetase (PfPRS). Using immunofluorescence data, we show that PfPRS is exclusively resident in the parasite cytoplasm within asexual blood stage parasites. The inhibitor HF interacts strongly with PfPRS in a non-competitive binding mode in presence or absence of ATP analog. Intriguingly, the two monomers that constitute dimeric PfPRS display significantly different conformations in their active site regions. The structural analyses presented here provide a framework for development of febrifugine derivatives that can seed development of new anti-malarials.
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Affiliation(s)
- Vitul Jain
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, 110067, India
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52
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Structural basis of malaria parasite lysyl-tRNA synthetase inhibition by cladosporin. ACTA ACUST UNITED AC 2014; 15:63-71. [PMID: 24935905 DOI: 10.1007/s10969-014-9182-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 05/24/2014] [Indexed: 10/25/2022]
Abstract
Malaria parasites inevitably develop drug resistance to anti-malarials over time. Hence the immediacy for discovering new chemical scaffolds to include in combination malaria drug therapy. The desirable attributes of new chemotherapeutic agents currently include activity against both liver and blood stage malaria parasites. One such recently discovered compound called cladosporin abrogates parasite growth via inhibition of Plasmodium falciparum lysyl-tRNA synthetase (PfKRS), an enzyme central to protein translation. Here, we present crystal structure of ternary PfKRS-lysine-cladosporin (PfKRS-K-C) complex that reveals cladosporin's remarkable ability to mimic the natural substrate adenosine and thereby colonize PfKRS active site. The isocoumarin fragment of cladosporin sandwiches between critical adenine-recognizing residues while its pyran ring fits snugly in the ribose-recognizing cavity. PfKRS-K-C structure highlights ample space within PfKRS active site for further chemical derivatization of cladosporin. Such derivatives may be useful against additional human pathogens that retain high conservation in cladosporin chelating residues within their lysyl-tRNA synthetase.
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53
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A dual-targeted aminoacyl-tRNA synthetase in Plasmodium falciparum charges cytosolic and apicoplast tRNACys. Biochem J 2014; 458:513-23. [PMID: 24428730 DOI: 10.1042/bj20131451] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Plasmodium parasites possess two endosymbiotic organelles: a mitochondrion and a relict plastid called the apicoplast. To accommodate the translational requirements of these organelles in addition to its cytosolic translation apparatus, the parasite must maintain a supply of charged tRNA molecules in each of these compartments. In the present study we investigate how the parasite manages these translational requirements for charged tRNACys with only a single gene for CysRS (cysteinyl-tRNA synthetase). We demonstrate that the single PfCysRS (Plasmodium falciparum CysRS) transcript is alternatively spliced, and, using a combination of endogenous and heterologous tagging experiments in both P. falciparum and Toxoplasma gondii, we show that CysRS isoforms traffic to the cytosol and apicoplast. PfCysRS can recognize and charge the eukaryotic tRNACys encoded by the Plasmodium nucleus as well as the bacterial-type tRNA encoded by the apicoplast genome, albeit with a preference for the eukaryotic type cytosolic tRNA. The results of the present study indicate that apicomplexan parasites have lost their original plastidic cysteinyl-tRNA synthetase, and have replaced it with a dual-targeted eukaryotic type CysRS that recognizes plastid and nuclear tRNACys. Inhibitors of the Plasmodium dual-targeted CysRS would potentially offer a therapy capable of the desirable immediate effects on parasite growth as well as the irreversibility of inhibitors that disrupt apicoplast inheritance.
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54
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Conformational landscapes for KMSKS loop in tyrosyl-tRNA synthetases. ACTA ACUST UNITED AC 2014; 15:45-61. [DOI: 10.1007/s10969-014-9178-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 03/08/2014] [Indexed: 01/20/2023]
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55
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Mailu BM, Ramasamay G, Mudeppa DG, Li L, Lindner SE, Peterson MJ, DeRocher AE, Kappe SHI, Rathod PK, Gardner MJ. A nondiscriminating glutamyl-tRNA synthetase in the plasmodium apicoplast: the first enzyme in an indirect aminoacylation pathway. J Biol Chem 2013; 288:32539-32552. [PMID: 24072705 PMCID: PMC3820887 DOI: 10.1074/jbc.m113.507467] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 09/23/2013] [Indexed: 11/06/2022] Open
Abstract
The malaria parasite Plasmodium falciparum and related organisms possess a relict plastid known as the apicoplast. Apicoplast protein synthesis is a validated drug target in malaria because antibiotics that inhibit translation in prokaryotes also inhibit apicoplast protein synthesis and are sometimes used for malaria prophylaxis or treatment. We identified components of an indirect aminoacylation pathway for Gln-tRNA(Gln) biosynthesis in Plasmodium that we hypothesized would be essential for apicoplast protein synthesis. Here, we report our characterization of the first enzyme in this pathway, the apicoplast glutamyl-tRNA synthetase (GluRS). We expressed the recombinant P. falciparum enzyme in Escherichia coli, showed that it is nondiscriminating because it glutamylates both apicoplast tRNA(Glu) and tRNA(Gln), determined its kinetic parameters, and demonstrated its inhibition by a known bacterial GluRS inhibitor. We also localized the Plasmodium berghei ortholog to the apicoplast in blood stage parasites but could not delete the PbGluRS gene. These data show that Gln-tRNA(Gln) biosynthesis in the Plasmodium apicoplast proceeds via an essential indirect aminoacylation pathway that is reminiscent of bacteria and plastids.
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Affiliation(s)
- Boniface M Mailu
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109
| | | | - Devaraja G Mudeppa
- the Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
| | - Ling Li
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109
| | - Scott E Lindner
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109
| | - Megan J Peterson
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109
| | - Amy E DeRocher
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109
| | - Stefan H I Kappe
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109,; the Department of Global Health, University of Washington, Seattle, Washington 98195
| | - Pradipsinh K Rathod
- the Department of Chemistry, University of Washington, Seattle, Washington 98195-1700; the Department of Global Health, University of Washington, Seattle, Washington 98195
| | - Malcolm J Gardner
- From the Seattle Biomedical Research Institute, Seattle, Washington 98109,; the Department of Global Health, University of Washington, Seattle, Washington 98195.
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56
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Khan S, Garg A, Sharma A, Camacho N, Picchioni D, Saint-Léger A, de Pouplana LR, Yogavel M, Sharma A. An appended domain results in an unusual architecture for malaria parasite tryptophanyl-tRNA synthetase. PLoS One 2013; 8:e66224. [PMID: 23776638 PMCID: PMC3680381 DOI: 10.1371/journal.pone.0066224] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 05/02/2013] [Indexed: 01/03/2023] Open
Abstract
Specific activation of amino acids by aminoacyl-tRNA synthetases (aaRSs) is essential for maintaining fidelity during protein translation. Here, we present crystal structure of malaria parasite Plasmodium falciparum tryptophanyl-tRNA synthetase (Pf-WRS) catalytic domain (AAD) at 2.6 Å resolution in complex with L-tryptophan. Confocal microscopy-based localization data suggest cytoplasmic residency of this protein. Pf-WRS has an unusual N-terminal extension of AlaX-like domain (AXD) along with linker regions which together seem vital for enzymatic activity and tRNA binding. Pf-WRS is not proteolytically processed in the parasites and therefore AXD likely provides tRNA binding capability rather than editing activity. The N-terminal domain containing AXD and linker region is monomeric and would result in an unusual overall architecture for Pf-WRS where the dimeric catalytic domains have monomeric AXDs on either side. Our PDB-wide comparative analyses of 47 WRS crystal structures also provide new mechanistic insights into this enzyme family in context conserved KMSKS loop conformations.
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Affiliation(s)
- Sameena Khan
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Ankur Garg
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Arvind Sharma
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Noelia Camacho
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Catalonia, Spain
| | - Daria Picchioni
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Catalonia, Spain
| | - Adélaïde Saint-Léger
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Catalonia, Spain
| | - Lluís Ribas de Pouplana
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Catalonia, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Catalonia, Spain
| | - Manickam Yogavel
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Amit Sharma
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
- * E-mail:
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57
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Khan S, Garg A, Camacho N, Van Rooyen J, Kumar Pole A, Belrhali H, Ribas de Pouplana L, Sharma V, Sharma A. Structural analysis of malaria-parasite lysyl-tRNA synthetase provides a platform for drug development. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:785-95. [PMID: 23633587 DOI: 10.1107/s0907444913001923] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Accepted: 01/18/2013] [Indexed: 01/29/2023]
Abstract
Aminoacyl-tRNA synthetases are essential enzymes that transmit information from the genetic code to proteins in cells and are targets for antipathogen drug development. Elucidation of the crystal structure of cytoplasmic lysyl-tRNA synthetase from the malaria parasite Plasmodium falciparum (PfLysRS) has allowed direct comparison with human LysRS. The authors' data suggest that PfLysRS is dimeric in solution, whereas the human counterpart can also adopt tetrameric forms. It is shown for the first time that PfLysRS is capable of synthesizing the signalling molecule Ap4a (diadenosine tetraphosphate) using ATP as a substrate. The PfLysRS crystal structure is in the apo form, such that binding to ATP will require rotameric changes in four conserved residues. Differences in the active-site regions of parasite and human LysRSs suggest the possibility of exploiting PfLysRS for selective inhibition. These investigations on PfLysRS further validate malarial LysRSs as attractive antimalarial targets and provide new structural space for the development of inhibitors that target pathogen LysRSs selectively.
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Affiliation(s)
- Sameena Khan
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi 110 067, India
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58
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Gowri VS, Ghosh I, Sharma A, Madhubala R. Unusual domain architecture of aminoacyl tRNA synthetases and their paralogs from Leishmania major. BMC Genomics 2012; 13:621. [PMID: 23151081 PMCID: PMC3532385 DOI: 10.1186/1471-2164-13-621] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 10/30/2012] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Leishmania major, a protozoan parasite, is the causative agent of cutaneous leishmaniasis. Due to the development of resistance against the currently available anti-leishmanial drugs, there is a growing need for specific inhibitors and novel drug targets. In this regards, aminoacyl tRNA synthetases, the linchpins of protein synthesis, have received recent attention among the kinetoplastid research community. This is the first comprehensive survey of the aminoacyl tRNA synthetases, their paralogs and other associated proteins from L. major. RESULTS A total of 26 aminoacyl tRNA synthetases were identified using various computational and bioinformatics tools. Phylogenetic analysis and domain architectures of the L. major aminoacyl tRNA synthetases suggest a probable archaeal/eukaryotic origin. Presence of additional domains or N- or C-terminal extensions in 11 aminoacyl tRNA synthetases from L. major suggests possibilities such as additional tRNA binding or oligomerization or editing activity. Five freestanding editing domains were identified in L. major. Domain assignment revealed a novel asparagine tRNA synthetase paralog, asparagine synthetase A which has been so far reported from prokaryotes and archaea. CONCLUSIONS A comprehensive bioinformatic analysis revealed 26 aminoacyl tRNA synthetases and five freestanding editing domains in L. major. Identification of two EMAP (endothelial monocyte-activating polypeptide) II-like proteins similar to human EMAP II-like proteins suggests their participation in multisynthetase complex formation. While the phylogeny of tRNA synthetases suggests a probable archaeal/eukaryotic origin, phylogeny of asparagine synthetase A strongly suggests a bacterial origin. The unique features identified in this work provide rationale for designing inhibitors against parasite aminoacyl tRNA synthetases and their paralogs.
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Affiliation(s)
- V S Gowri
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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59
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Jackson KE, Pham JS, Kwek M, De Silva NS, Allen SM, Goodman CD, McFadden GI, Ribas de Pouplana L, Ralph SA. Dual targeting of aminoacyl-tRNA synthetases to the apicoplast and cytosol in Plasmodium falciparum. Int J Parasitol 2012; 42:177-86. [DOI: 10.1016/j.ijpara.2011.11.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/22/2011] [Accepted: 11/23/2011] [Indexed: 11/16/2022]
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60
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Khan S, Sharma A, Jamwal A, Sharma V, Pole AK, Thakur KK, Sharma A. Uneven spread of cis- and trans-editing aminoacyl-tRNA synthetase domains within translational compartments of P. falciparum. Sci Rep 2011; 1:188. [PMID: 22355703 PMCID: PMC3240968 DOI: 10.1038/srep00188] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 11/28/2011] [Indexed: 11/24/2022] Open
Abstract
Accuracy of aminoacylation is dependent on maintaining fidelity during attachment of amino acids to cognate tRNAs. Cis- and trans-editing protein factors impose quality control during protein translation, and 8 of 36 Plasmodium falciparum aminoacyl-tRNA synthetase (aaRS) assemblies contain canonical putative editing modules. Based on expression and localization profiles of these 8 aaRSs, we propose an asymmetric distribution between the parasite cytoplasm and its apicoplast of putative editing-domain containing aaRSs. We also show that the single copy alanyl- and threonyl-tRNA synthetases are dually targeted to parasite cytoplasm and apicoplast. This bipolar presence of two unique synthetases presents opportunity for inhibitor targeting their aminoacylation and editing activities in twin parasite compartments. We used this approach to identify specific inhibitors against the alanyl- and threonyl-tRNA synthetases. Further development of such inhibitors may lead to anti-parasitics which simultaneously block protein translation in two key parasite organelles, a strategy of wider applicability for pathogen control.
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Affiliation(s)
- Sameena Khan
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
- These three authors have contributed equally to this work
| | - Arvind Sharma
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
- These three authors have contributed equally to this work
| | - Abhishek Jamwal
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
- These three authors have contributed equally to this work
| | - Vinay Sharma
- Department of Bioscience and Biotechnology, Banasthali Vidyapith University, Banasthali, Rajasthan 304 022, India
| | - Anil Kumar Pole
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
| | - Kamal Kishor Thakur
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
| | - Amit Sharma
- Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110 067, India
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61
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Malaria parasite tyrosyl-tRNA synthetase secretion triggers pro-inflammatory responses. Nat Commun 2011; 2:530. [DOI: 10.1038/ncomms1522] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 09/29/2011] [Indexed: 11/08/2022] Open
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62
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Protein translation in Plasmodium parasites. Trends Parasitol 2011; 27:467-76. [PMID: 21741312 DOI: 10.1016/j.pt.2011.05.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/13/2011] [Accepted: 05/16/2011] [Indexed: 12/18/2022]
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63
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Crepin T, Peterson F, Haertlein M, Jensen D, Wang C, Cusack S, Kron M. A hybrid structural model of the complete Brugia malayi cytoplasmic asparaginyl-tRNA synthetase. J Mol Biol 2010; 405:1056-69. [PMID: 21134380 DOI: 10.1016/j.jmb.2010.11.049] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 11/18/2010] [Accepted: 11/22/2010] [Indexed: 11/15/2022]
Abstract
Aminoacyl-tRNA synthetases are validated molecular targets for anti-infective drug discovery because of their essentiality in protein synthesis. Thanks to genome sequencing, it is now possible to systematically study aminoacyl-tRNA synthetases from human eukaryotic parasites as putative targets for novel drug discovery. As part of a program targeting class IIb asparaginyl-tRNA synthetases (AsnRS) from the parasitic nematode Brugia malayi for anti-filarial drugs, we report the complete structure of a eukaryotic AsnRS. Metazoan and fungal AsnRS differ from their bacterial homologues by the addition of a conserved N-terminal extension of about 110 residues whose structure we have determined by solution NMR for the B. malayi enzyme. In addition, we solved by X-ray crystallography a series of structures of the catalytically active N-terminally truncated enzyme (residues 112-548), allowing the structural basis for the mechanism of asparagine activation to be elucidated. The N-terminal domain contains a structured region with a novel fold featuring a lysine-rich helix that is shown by NMR to interact with tRNA. This is connected by an unstructured tether to the remainder of the enzyme, which is highly similar to the known structure of bacterial AsnRS. These data enable a model of the complete AsnRS-tRNA complex to be constructed.
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MESH Headings
- Amino Acid Sequence
- Animals
- Aspartate-tRNA Ligase/chemistry
- Aspartate-tRNA Ligase/genetics
- Aspartate-tRNA Ligase/metabolism
- Base Sequence
- Brugia malayi/enzymology
- Brugia malayi/genetics
- Catalytic Domain
- Crystallography, X-Ray
- Cytoplasm/enzymology
- DNA Primers/genetics
- Enzyme Activation
- Helminth Proteins/chemistry
- Helminth Proteins/genetics
- Helminth Proteins/metabolism
- Humans
- Models, Molecular
- Molecular Sequence Data
- Nuclear Magnetic Resonance, Biomolecular
- Protein Structure, Tertiary
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- Thibaut Crepin
- European Molecular Biology Laboratory, Grenoble Outstation, 6 rue Jules Horowitz, 38142 Grenoble Cedex 9, France
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64
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Pino P, Aeby E, Foth BJ, Sheiner L, Soldati T, Schneider A, Soldati-Favre D. Mitochondrial translation in absence of local tRNA aminoacylation and methionyl tRNA Met formylation in Apicomplexa. Mol Microbiol 2010; 76:706-18. [PMID: 20374492 DOI: 10.1111/j.1365-2958.2010.07128.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apicomplexans possess three translationally active compartments: the cytosol, a single tubular mitochondrion, and a vestigial plastid organelle called apicoplast. Mitochondrion and apicoplast are of bacterial evolutionary origin and therefore depend on a bacterial-like translation machinery. The minimal mitochondrial genome contains only three ORFs, and in Toxoplasma gondii the absence of mitochondrial tRNA genes is compensated for by the import of cytosolic eukaryotic tRNAs. Although all compartments require a complete set of charged tRNAs, the apicomplexan nuclear genomes do not hold sufficient aminoacyl-tRNA synthetase (aaRSs) genes to be targeted individually to each compartment. This study reveals that aaRSs are either cytosolic, apicoplastic or shared between the two compartments by dual targeting but are absent from the mitochondrion. Consequently, tRNAs are very likely imported in their aminoacylated form. Furthermore, the unexpected absence of tRNA(Met) formyltransferase and peptide deformylase implies that the requirement for a specialized formylmethionyl-tRNA(Met) for translation initiation is bypassed in the mitochondrion of Apicomplexa.
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Affiliation(s)
- Paco Pino
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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