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Fang C, Ma Y, Yuan L, Wang Z, Yang R, Zhou Z, Liu T, Tian Z. Chloroplast DNA Underwent Independent Selection from Nuclear Genes during Soybean Domestication and Improvement. J Genet Genomics 2016; 43:217-21. [PMID: 27090605 DOI: 10.1016/j.jgg.2016.01.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 01/06/2016] [Accepted: 01/08/2016] [Indexed: 11/22/2022]
Affiliation(s)
- Chao Fang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanming Ma
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; Beijing University of Agriculture, Beijing 102206, China
| | - Lichai Yuan
- The Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Beijing 100193, China
| | - Zheng Wang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Rui Yang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhengkui Zhou
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Tengfei Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhixi Tian
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
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2
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On the origin of chloroplasts, import mechanisms of chloroplast-targeted proteins, and loss of photosynthetic ability — review. Folia Microbiol (Praha) 2009; 54:303-21. [DOI: 10.1007/s12223-009-0048-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 03/31/2009] [Indexed: 10/20/2022]
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3
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Lv HX, Guo GQ, Yang ZN. Translocons on the inner and outer envelopes of chloroplasts share similar evolutionary origin in Arabidopsis thaliana. J Evol Biol 2009; 22:1418-28. [PMID: 19460081 DOI: 10.1111/j.1420-9101.2009.01755.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process of importing nuclear encoded proteins into chloroplasts is mediated by the Translocons on the Outer/Inner Envelope of Chloroplasts (TOC and TIC complex). The ancestor of the TOC complex was formed by pre-existing proteins from the cyanobacterial ancestor; other proteins recruited from the host cell or cyanobacterial ancestor were subsequently integrated into the complex. However, little is known about the origin of the TIC complex. In this work, the origin of the TIC complex was investigated through one of its channel proteins, AtTic21. Phylogenetic analysis suggested that AtTic21 is conserved in photosynthetic organisms. AtTic21 showed 33% sequence identity to a Synechocystis protein SynTic21. The successful genetic complementation of an AtTic21 knockout mutant by SynTic21 plus the transit peptide coding sequence of AtTic21 suggested that SynTic21 is an ortholog of AtTic21. The sequence and functional conservation between SynTic21 and AtTic21 suggested that the TIC complex shares a similar evolutionary origin to the TOC complex.
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Affiliation(s)
- H-X Lv
- Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou, China
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5
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Reumann S, Inoue K, Keegstra K. Evolution of the general protein import pathway of plastids (review). Mol Membr Biol 2005; 22:73-86. [PMID: 16092526 DOI: 10.1080/09687860500041916] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The evolutionary process that transformed a cyanobacterial endosymbiont into contemporary plastids involved not only inheritance but also invention. Because gram-negative bacteria lack a system for polypeptide import, the envelope translocon complex of the general protein import pathway was the most important invention of organelle evolution resulting in a pathway to import back into plastids those nuclear-encoded proteins supplemented with a transit peptide. Genome information of cyanobacteria, phylogenetically diverse plastids, and the nuclei of the first red alga, a diatom, and Arabidopsis thaliana allows us to trace back the evolutionary origin of the twelve currently known translocon components and to partly deduce their assembly sequence. Development of the envelope translocon was initiated by recruitment of a cyanobacterial homolog of the protein-import channel Toc75, which belongs to a ubiquitous and essential family of Omp85/D15 outer membrane proteins of gram-negative bacteria that mediate biogenesis of beta-barrel proteins. Likewise, three other translocon subunits (Tic20, Tic22, and Tic55) and several stromal chaperones have been inherited from the ancestral cyanobacterium and modified to take over the novel function of precursor import. Most of the remaining subunits seem to be of eukaryotic origin, recruited from pre-existing nuclear genes. The next subunits that joined the evolving protein import complex likely were Toc34 and Tic110, as indicated by the presence of homologous genes in the red alga Cyanidioschyzon merolae, followed by the stromal processing peptidase, members of the Toc159 receptor family, Toc64, Tic40, and finally some regulatory redox components (Tic62, Tic32), all of which were probably required to increase specificity and efficiency of precursor import.
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Affiliation(s)
- Sigrun Reumann
- Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Göttingen, Germany.
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6
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Moslavac S, Mirus O, Bredemeier R, Soll J, von Haeseler A, Schleiff E. Conserved pore-forming regions in polypeptide-transporting proteins. FEBS J 2005; 272:1367-78. [PMID: 15752354 DOI: 10.1111/j.1742-4658.2005.04569.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transport of solutes and polypeptides across membranes is an essential process for every cell. In the past, much focus has been placed on helical transporters. Recently, the beta-barrel-shaped transporters have also attracted some attention. The members of this family are found in the outer bacterial membrane and the outer membrane of endosymbiotically derived organelles. Here we analyze the features and the evolutionary development of a specified translocator family, namely the beta-barrel-shaped polypeptide-transporters. We identified sequence motifs, which characterize all transporters of this family, as well as motifs specific for a certain subgroup of proteins of this class. The general motifs are related to the structural composition of the pores. Further analysis revealed a defined distance of two motifs to the C-terminal portion of the proteins. Furthermore, the evolutionary relationship of the proteins and the motifs are discussed.
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7
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Nassoury N, Morse D. Protein targeting to the chloroplasts of photosynthetic eukaryotes: getting there is half the fun. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1743:5-19. [PMID: 15777835 DOI: 10.1016/j.bbamcr.2004.09.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 08/10/2004] [Accepted: 09/17/2004] [Indexed: 11/19/2022]
Abstract
The plastids of many algae are surrounded by three or four membranes, thought to be a consequence of their evolutionary origin through secondary endosymbiosis between photosynthetic and non-photosynthetic eukaryotes. Each membrane constitutes a barrier to the passage of proteins, so protein targeting in these complex plastids has an extra level of difficulty when compared to higher plants. In the latter, protein translocation across the two membranes uses multi-protein complexes that together import proteins possessing an N-terminal leader sequence rich in serine and threonine (S/T). In contrast, while targeting to most complex plastids also involves an S/T-rich region, this region is preceded by an N-terminal hydrophobic signal peptide. This arrangement of peptide sequences suggests that proteins directed to complex plastids pass through the ER, as do other proteins with hydrophobic signal peptides. However, this simplistic view is not always easy to reconcile with what is known about the different secondary plastids. In the first group, with plastids bounded by three membranes, plastid-directed proteins do indeed arrive in Golgi-derived vesicles, but a second hydrophobic region follows the S/T-rich region in all leaders. In the second group, where four membranes completely surround the plastids, it is still not known how the proteins arrive at the plastids, and in addition, one member of this group uses a targeting signal rich in asparagine and lysine in place of the S/T-rich region. In the third group, the fourth bounding membrane is contiguous with the ER, but it is not clear what distinguishes plastid membranes from others in the endomembrane system. Knowing what to expect is important, as genomic sequencing programs may soon be turning up some of the missing pieces in these translocation puzzles.
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Affiliation(s)
- Nasha Nassoury
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 Sherbrooke est, Montreal, Quebec, Canada H1X 2B2
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8
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Affiliation(s)
- Jürgen Soll
- Department für Biologie I, Botanik, Ludwig-Maximilians-Universität München, Menzingerstrasse 67, D-80638 Munich, Germany.
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9
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Martin W, Rujan T, Richly E, Hansen A, Cornelsen S, Lins T, Leister D, Stoebe B, Hasegawa M, Penny D. Evolutionary analysis of Arabidopsis, cyanobacterial, and chloroplast genomes reveals plastid phylogeny and thousands of cyanobacterial genes in the nucleus. Proc Natl Acad Sci U S A 2002; 99:12246-51. [PMID: 12218172 PMCID: PMC129430 DOI: 10.1073/pnas.182432999] [Citation(s) in RCA: 741] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Chloroplasts were once free-living cyanobacteria that became endosymbionts, but the genomes of contemporary plastids encode only approximately 5-10% as many genes as those of their free-living cousins, indicating that many genes were either lost from plastids or transferred to the nucleus during the course of plant evolution. Previous estimates have suggested that between 800 and perhaps as many as 2,000 genes in the Arabidopsis genome might come from cyanobacteria, but genome-wide phylogenetic surveys that could provide direct estimates of this number are lacking. We compared 24,990 proteins encoded in the Arabidopsis genome to the proteins from three cyanobacterial genomes, 16 other prokaryotic reference genomes, and yeast. Of 9,368 Arabidopsis proteins sufficiently conserved for primary sequence comparison, 866 detected homologues only among cyanobacteria and 834 other branched with cyanobacterial homologues in phylogenetic trees. Extrapolating from these conserved proteins to the whole genome, the data suggest that approximately 4,500 of Arabidopsis protein-coding genes ( approximately 18% of the total) were acquired from the cyanobacterial ancestor of plastids. These proteins encompass all functional classes, and the majority of them are targeted to cell compartments other than the chloroplast. Analysis of 15 sequenced chloroplast genomes revealed 117 nuclear-encoded proteins that are also still present in at least one chloroplast genome. A phylogeny of chloroplast genomes inferred from 41 proteins and 8,303 amino acids sites indicates that at least two independent secondary endosymbiotic events have occurred involving red algae and that amino acid composition bias in chloroplast proteins strongly affects plastid genome phylogeny.
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Affiliation(s)
- William Martin
- Institut für Botanik, Heinrich Heine Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
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10
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Abstract
The vast majority of chloroplast proteins are synthesized in precursor form on cytosolic ribosomes. Chloroplast precursor proteins have cleavable, N-terminal targeting signals called transit peptides. Transit peptides direct precursor proteins to the chloroplast in an organelle-specific way. They can be phosphorylated by a cytosolic protein kinase, and this leads to the formation of a cytosolic guidance complex. The guidance complex--comprising precursor, hsp70 and 14-3-3 proteins, as well as several unidentified components--docks at the outer envelope membrane. Translocation of precursor proteins across the envelope is achieved by the joint action of molecular machines called Toc (translocon at the outer envelope membrane of chloroplasts) and Tic (translocon at the inner envelope membrane of chloroplasts), respectively. The action of the Toc/Tic apparatus requires the hydrolysis of ATP and GTP at different levels, indicating energetic requirements and regulatory properties of the import process. The main subunits of the Toc and Tic complexes have been identified and characterized in vivo, in organello and in vitro. Phylogenetic evidence suggests that several translocon subunits are of cyanobacterial origin, indicating that today's import machinery was built around a prokaryotic core.
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Affiliation(s)
- Paul Jarvis
- Department of Biology, University of Leicester, UK.
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11
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Eckart K, Eichacker L, Sohrt K, Schleiff E, Heins L, Soll J. A Toc75-like protein import channel is abundant in chloroplasts. EMBO Rep 2002; 3:557-62. [PMID: 12034753 PMCID: PMC1084144 DOI: 10.1093/embo-reports/kvf110] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2002] [Revised: 03/20/2002] [Accepted: 04/04/2002] [Indexed: 11/12/2022] Open
Abstract
Chloroplasts import post-translationally most of their constituent polypeptides via two distinct translocon units located in the outer and inner envelope. The protein import channel of the translocon of the outer envelope of chloroplasts, Toc75, is the most abundant protein in that membrane. We identify a novel Toc75 homologous protein, atToc75-V, a prominent protein that is clearly localized in the chloroplastic outer envelope. Phylogenetic analysis indicates that Toc75-V is more closely related to its prokaryotic ancestors than to Toc75 from plants. The presence of a second translocation channel suggests that alternative, previously unrecognized import routes into chloroplasts might exist.
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Affiliation(s)
- Kerstin Eckart
- Department für Biologie I, Menzinger Strasse 67, Ludwig-Maximilians-Universität, D-80638 München, Germany
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12
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Abstract
The vast majority of chloroplast proteins are synthesized in precursor form on cytosolic ribosomes. Chloroplast precursor proteins have cleavable, N-terminal targeting signals called transit peptides. Transit peptides direct precursor proteins to the chloroplast in an organelle-specific way. They can be phosphorylated by a cytosolic protein kinase, and this leads to the formation of a cytosolic guidance complex. The guidance complex--comprising precursor, hsp70 and 14-3-3 proteins, as well as several unidentified components--docks at the outer envelope membrane. Translocation of precursor proteins across the envelope is achieved by the joint action of molecular machines called Toc (translocon at the outer envelope membrane of chloroplasts) and Tic (translocon at the inner envelope membrane of chloroplasts), respectively. The action of the Toc/Tic apparatus requires the hydrolysis of ATP and GTP at different levels, indicating energetic requirements and regulatory properties of the import process. The main subunits of the Toc and Tic complexes have been identified and characterized in vivo, in organello and in vitro. Phylogenetic evidence suggests that several translocon subunits are of cyanobacterial origin, indicating that today's import machinery was built around a prokaryotic core.
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Affiliation(s)
- P Jarvis
- Department of Biology, University of Leicester, UK.
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13
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Dalbey RE, Kuhn A. Evolutionarily related insertion pathways of bacterial, mitochondrial, and thylakoid membrane proteins. Annu Rev Cell Dev Biol 2001; 16:51-87. [PMID: 11031230 DOI: 10.1146/annurev.cellbio.16.1.51] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The inner membranes of eubacteria and mitochondria, as well as the chloroplast thylakoid membrane, contain essential proteins that function in oxidative phosphorylation and electron transport processes or in photosynthesis. Because most of the organellar proteins are nuclear encoded, they are synthesized in the cytoplasm and subsequently imported into the organelle before they are inserted into the membrane. This review focuses on the pathways of protein insertion into the inner membrane of eubacteria and mitochondria and into the chloroplast thylakoid membrane. In many respects, insertion of proteins into the inner membrane of bacteria is a process similar to that used by proteins of the thylakoid membrane. In both of these systems a signal recognition particle (SRP) and a SecYE-translocase are involved, as in translocation into the endoplasmic reticulum. The pathway of proteins into the mitochondrial membranes appears to be different in that it involves no SecYE-like components. A conservative pathway, recently identified in mitochondria, involves the Oxa1 protein for the insertion of proteins from the matrix. The presence of Oxa1 homologues in eubacteria and chloroplasts suggests that this pathway is evolutionarily conserved.
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Affiliation(s)
- R E Dalbey
- Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
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Abstract
Plastids originated from an endosymbiotic event between an early eukaryotic host cell and an ancestor of today's cyanobacteria. During the events by which the engulfed endosymbiont was transformed into a permanent organelle, many genes were transferred from the plastidal genome to the nucleus of the host cell. Proteins encoded by these genes are synthesised in the cytosol and subsequently translocated into the plastid. Therefore they contain an N-terminal cleavable transit sequence that is necessary for translocation. The sequence is plastid-specific, thus preventing mistargeting into other organelles. Receptors embedded into the outer envelope of the plastid recognise the transit sequences, and precursor proteins are translocated into the chloroplast by a proteinaceous import machinery located in both the outer and inner envelopes. Inside the stroma the transit sequences are cleaved off and the proteins are further routed to their final locations within the plastid.
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Affiliation(s)
- U C Vothknecht
- Botanisches Institut der Christian-Albrechts-Universität Kiel, Germany
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15
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Abstract
Protein translocation across the bacterial cytoplasmic membrane has been studied extensively in Escherichia coli. The identification of the components involved and subsequent reconstitution of the purified translocation reaction have defined the minimal constituents that allowed extensive biochemical characterization of the so-called translocase. This functional enzyme complex consists of the SecYEG integral membrane protein complex and a peripherally bound ATPase, SecA. Under translocation conditions, four SecYEG heterotrimers assemble into one large protein complex, forming a putative protein-conducting channel. This tetrameric arrangement of SecYEG complexes and the highly dynamic SecA dimer together form a proton-motive force- and ATP-driven molecular machine that drives the stepwise translocation of targeted polypeptides across the cytoplasmic membrane. Recent findings concerning the translocase structure and mechanism of protein translocation are discussed and shine new light on controversies in the field.
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Affiliation(s)
- E H Manting
- Department of Microbiology and Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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16
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Affiliation(s)
- E Hoiczyk
- Laboratory of Cell Biology, The Rockefeller University, New York, New York 10021-6399, USA
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Baumeister S, Burgwedel A, Maier UG, Lingelbach K. Reconstitution of protein transport across the vacuolar membrane in Plasmodium falciparum-infected permeabilized erythrocytes. NOVARTIS FOUNDATION SYMPOSIUM 2000; 226:145-54; discussion 154-6. [PMID: 10645544 DOI: 10.1002/9780470515730.ch11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The parasite Plasmodium falciparum induces morphological and biochemical alterations of its host erythrocyte. Some of these changes are mediated by parasite proteins that are transported to specific destinations within the erythrocyte or to the erythrocyte plasma membrane. The pathways underlying this transport are still unknown. We anticipate that at least some aspects of these pathways may be biologically unique and therefore potential targets for chemotherapeutic intervention. We have utilized bacterial pore-forming proteins to establish an experimental system that allows selective permeabilization of the erythrocyte plasma membrane, without affecting the integrity of the vacuolar membrane and the parasite plasma membrane, in order to study protein transport from the parasite into the host erythrocyte. Physiological properties of the parasite within permeabilized erythrocytes, such as the ability to synthesize proteins, will be described. The permeabilization of infected erythrocytes has allowed the dissection of individual steps in protein transport from the parasite surface across the vacuolar membrane. Possible pathways involved in the trafficking of parasite proteins within the erythrocyte cytosol, i.e. in a cell that normally has no need to transport proteins, will be discussed.
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Affiliation(s)
- S Baumeister
- FB Biologie/Zoologie, Philipps Universität Marburg, Germany
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18
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Abstract
The bacterial origins of plastid division and protein import by plastids are beginning to emerge - thanks largely to the availability of a total genome sequence for a cyanobacterium. Despite existing for hundreds of millions of years within the plant cell host, the chloroplast endosymbiont retains clear hallmarks of its bacterial ancestry. Plastid division relies on proteins that are also responsible for bacterial division, although may of the genes for these proteins have been confiscated by the host. Plastid protein import on the other hand relies on proteins that seem to have functioned originally as exporters but that have now been persuaded to operate in the reverse direction to traffic proteins from the host cell into the endosymbiont.
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Affiliation(s)
- G I McFadden
- Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville, VIC 3010, Australia. . edu.au
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19
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Abstract
Resolving the order of events that occurred during the transition from prokaryotic to eukaryotic cells remains one of the greatest problems in cell evolution. One view, the Archezoa hypothesis, proposes that the endosymbiotic origin of mitochondria occurred relatively late in eukaryotic evolution and that several mitochondrion-lacking protist groups diverged before the establishment of the organelle. Phylogenies based on small subunit ribosomal RNA and several protein-coding genes supported this proposal, placing amitochondriate protists such as diplomonads, parabasalids, and Microsporidia as the earliest diverging eukaryotic lineages. However, trees of other molecules, such as tubulins, heat shock protein 70, TATA box-binding protein, and the largest subunit of RNA polymerase II, indicate that Microsporidia are not deeply branching eukaryotes but instead are close relatives of the Fungi. Furthermore, recent discoveries of mitochondrion-derived genes in the nuclear genomes of entamoebae, Microsporidia, parabasalids, and diplomonads suggest that these organisms likely descend from mitochondrion-bearing ancestors. Although several protist lineages formally remain as candidates for Archezoa, most evidence suggests that the mitochondrial endosymbiosis took place prior to the divergence of all extant eukaryotes. In addition, discoveries of proteobacterial-like nuclear genes coding for cytoplasmic proteins indicate that the mitochondrial symbiont may have contributed more to the eukaryotic lineage than previously thought. As genome sequence data from parabasalids and diplomonads accumulate, it is becoming clear that the last common ancestor of these protist taxa and other extant eukaryotic groups already possessed many of the complex features found in most eukaryotes but lacking in prokaryotes. However, our confidence in the deeply branching position of diplomonads and parabasalids among eukaryotes is weakened by conflicting phylogenies and potential sources of artifact. Our current picture of early eukaryotic evolution is in a state of flux.
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Martin W. A briefly argued case that mitochondria and plastids are descendants of endosymbionts, but that the nuclear compartment is not. Proc Biol Sci 1999. [DOI: 10.1098/rspb.1999.0792] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- William Martin
- Institut für Genetik,Technische Universität Braunschweig, Spielmannstrasse 7, D–38023 Braunschweig, Germany
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21
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Bölter B, Soll J, Schulz A, Hinnah S, Wagner R. Origin of a chloroplast protein importer. Proc Natl Acad Sci U S A 1998; 95:15831-6. [PMID: 9861056 PMCID: PMC28130 DOI: 10.1073/pnas.95.26.15831] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/1998] [Indexed: 11/18/2022] Open
Abstract
During evolution, chloroplasts have relinquished the majority of their genes to the nucleus. The products of transferred genes are imported into the organelle with the help of an import machinery that is distributed across the inner and outer plastid membranes. The evolutionary origin of this machinery is puzzling because, in the putative predecessors, the cyanobacteria, the outer two membranes, the plasma membrane, and the lipopolysaccharide layer lack a functionally similar protein import system. A 75-kDa protein-conducting channel in the outer envelope of pea chloroplasts, Toc75, shares approximately 22% amino acid identity to a similarly sized protein, designated SynToc75, encoded in the Synechocystis PCC6803 genome. Here we show that SynToc75 is located in the outer membrane (lipopolysaccharide layer) of Synechocystis PCC6803 and that SynToc75 forms a voltage-gated, high conductance channel with a high affinity for polyamines and peptides in reconstituted liposomes. These findings suggest that a component of the chloroplast protein import system, Toc75, was recruited from a preexisting channel-forming protein of the cyanobacterial outer membrane. Furthermore, the presence of a protein in the chloroplastic outer envelope homologous to a cyanobacterial protein provides support for the prokaryotic nature of this chloroplastic membrane.
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Affiliation(s)
- B Bölter
- Botanisches Institut, Universität Kiel, Am Botanischen Garten 1-9, D-24118 Kiel, Germany
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22
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Bölter B, May T, Soll J. A protein import receptor in pea chloroplasts, Toc86, is only a proteolytic fragment of a larger polypeptide. FEBS Lett 1998; 441:59-62. [PMID: 9877165 DOI: 10.1016/s0014-5793(98)01525-7] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The protein import complex of the chloroplastic outer envelope (Toc-complex) contains a prominent subunit of 86 kDa molecular weight (Toc86). Toc86 was identified as a putative precursor receptor. The Arabidopsis genome sequencing project indicates that Toc86 represents only a proteolytic fragment of a larger polypeptide of 160 kDa. The 160-kDa protein, which we name Toc160, is only present in significant amounts in pea chloroplasts isolated under stringent conditions. The capacity of chloroplasts to import an in vitro translated precursor protein correlates well with the integrity of Toc160. We conclude that Toc160 is still a bonafide subunit of the protein import machinery of chloroplasts.
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Affiliation(s)
- B Bölter
- Botanisches Institut, Universität Kiel, Germany
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23
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Martin W, Herrmann RG. Gene transfer from organelles to the nucleus: how much, what happens, and Why? PLANT PHYSIOLOGY 1998; 118:9-17. [PMID: 9733521 PMCID: PMC1539188 DOI: 10.1104/pp.118.1.9] [Citation(s) in RCA: 443] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- W Martin
- Institut fur Genetik, Technische Universitat Braunschweig, Spielmannstrasse 7, D-38023 Braunschweig, Germany (W.M.)
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