101
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Kroll D, Meierhoff K, Bechtold N, Kinoshita M, Westphal S, Vothknecht UC, Soll J, Westhoff P. VIPP1, a nuclear gene of Arabidopsis thaliana essential for thylakoid membrane formation. Proc Natl Acad Sci U S A 2001; 98:4238-42. [PMID: 11274447 PMCID: PMC31209 DOI: 10.1073/pnas.061500998] [Citation(s) in RCA: 262] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2000] [Indexed: 11/18/2022] Open
Abstract
The conversion of light to chemical energy by the process of photosynthesis is localized to the thylakoid membrane network in plant chloroplasts. Although several pathways have been described that target proteins into and across the thylakoids, little is known about the origin of this membrane system or how the lipid backbone of the thylakoids is transported and fused with the target membrane. Thylakoid biogenesis and maintenance seem to involve the flow of membrane elements via vesicular transport. Here we show by mutational analysis that deletion of a single gene called VIPP1 (vesicle-inducing protein in plastids 1) is deleterious to thylakoid membrane formation. Although VIPP1 is a hydrophilic protein it is found in both the inner envelope and the thylakoid membranes. In VIPP1 deletion mutants vesicle formation is abolished. We propose that VIPP1 is essential for the maintenance of thylakoids by a transport pathway not previously recognized.
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Affiliation(s)
- D Kroll
- Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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102
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Westphal S, Heins L, Soll J, Vothknecht UC. Vipp1 deletion mutant of Synechocystis: a connection between bacterial phage shock and thylakoid biogenesis? Proc Natl Acad Sci U S A 2001; 98:4243-8. [PMID: 11274448 PMCID: PMC31210 DOI: 10.1073/pnas.061501198] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plant chloroplasts originated from an endosymbiotic event by which an ancestor of contemporary cyanobacteria was engulfed by an early eukaryotic cell and then transformed into an organelle. Oxygenic photosynthesis is the specific feature of cyanobacteria and chloroplasts, and the photosynthetic machinery resides in an internal membrane system, the thylakoids. The origin and genesis of thylakoid membranes, which are essential for oxygenic photosynthesis, are still an enigma. Vipp1 (vesicle-inducing protein in plastids 1) is a protein located in both the inner envelope and the thylakoids of Pisum sativum and Arabidopsis thaliana. In Arabidopsis disruption of the VIPP1 gene severely affects the plant's ability to form properly structured thylakoids and as a consequence to carry out photosynthesis. In contrast, Vipp1 in Synechocystis appears to be located exclusively in the plasma membrane. Yet, as in higher plants, disruption of the VIPP1 gene locus leads to the complete loss of thylakoid formation. So far VIPP1 genes are found only in organisms carrying out oxygenic photosynthesis. They share sequence homology with a subunit encoded by the bacterial phage shock operon (PspA) but differ from PspA by a C-terminal extension of about 30 amino acids. In two cyanobacteria, Synechocystis and Anabaena, both a VIPP1 and a pspA gene are present, and phylogenetic analysis indicates that VIPP1 originated from a gene duplication of the latter and thereafter acquired its new function. It also appears that the C-terminal extension that discriminates VIPP1 proteins from PspA is important for its function in thylakoid formation.
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Affiliation(s)
- S Westphal
- Botanisches Institut, Christian-Albrecht-Universität Kiel, Am Botanischen Garten 1-9, 24118 Kiel, Germany
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103
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Rujan T, Martin W. How many genes in Arabidopsis come from cyanobacteria? An estimate from 386 protein phylogenies. Trends Genet 2001; 17:113-20. [PMID: 11226586 DOI: 10.1016/s0168-9525(00)02209-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It is well known that chloroplasts and mitochondria donated many genes to nuclear chromosomes during evolution - but how many is "many"? A sample of 3961 Arabidopsis nuclear protein-coding genes was compared with the complete set of proteins from yeast and 17 reference prokaryotic genomes, including one cyanobacterium (the lineage from which plastids arose). The analysis of 386 phylogenetic trees distilled from these data suggests that between approximately 400 (1.6%) and approximately 2200 (9.2%) of Arabidopsis nuclear genes stem from cyanobacteria. The degree of conservation preserved in protein sequences in addition to lateral gene transfer between free-living prokaryotes pose substantial challenges to genome phylogenetics.
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Affiliation(s)
- T Rujan
- Institute of Botany III, Universität Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
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104
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Gabriel K, Buchanan SK, Lithgow T. The alpha and the beta: protein translocation across mitochondrial and plastid outer membranes. Trends Biochem Sci 2001; 26:36-40. [PMID: 11165515 DOI: 10.1016/s0968-0004(00)01684-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In the evolution of mitochondria and plastids from endosymbiotic bacteria, most of the proteins that make up these organelles have become encoded by nuclear genes and must therefore be transported across the organellar membranes, following synthesis in the cytosol. The core component of the protein translocation machines in both the mitochondrial and plastid outer membranes appears to be a beta-barrel protein, perhaps a relic from their bacterial ancestry, distinguishing these translocases from the alpha-helical-based protein translocation pores found in all other eukaryotic membranes.
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Affiliation(s)
- K Gabriel
- Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Parkville, 3010, Australia
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105
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106
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Sergeyenko TV, Los DA. Identification of secreted proteins of the cyanobacterium Synechocystis sp. strain PCC 6803. FEMS Microbiol Lett 2000; 193:213-6. [PMID: 11111026 DOI: 10.1111/j.1574-6968.2000.tb09426.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We investigated the spectrum of secreted proteins in the cyanobacterium Synechocystis, and identified these proteins by amino-terminal sequencing. In total, seven sequences have been determined that corresponded to the proteins Sll0044, Sll1694, Sll1891, Slr0924, Slr0841, Slr0168, and Slr1855. The protein Sll1694 of 18 kDa that formed one of two major bands on SDS-PAGE was identified as cyanobacterial pilin, PilA. The amino-terminal sequence of another protein that formed a second major band was blocked. The analysis of the data revealed that five of seven proteins had distinct putative leader sequences for secretion.
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Affiliation(s)
- T V Sergeyenko
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya street 35, 127276, Moscow, Russia
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107
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Abstract
It is thought that two to three thousand different proteins are targeted to the chloroplast, and the 'transit peptides' that act as chloroplast targeting sequences are probably the largest class of targeting sequences in plants. At a primary structural level, transit peptide sequences are highly divergent in length, composition and organization. An emerging concept suggests that transit peptides contain multiple domains that provide either distinct or overlapping functions. These functions include direct interaction with envelope lipids, chloroplast receptors and the stromal processing peptidase. The genomic organization of transit peptides suggests that these domains might have originated from distinct exons, which were shuffled and streamlined throughout evolution to yield a modern, multifunctional transit peptide. Although still poorly characterized, this evolutionary process could yield transit peptides with different domain organizations. The plasticity of transit peptide design is consistent with the diverse biological functions of chloroplast proteins.
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Affiliation(s)
- B D Bruce
- Dept of Biochemistry, Cellular and Molecular Biology Department, The Center for Legume Research, University of Tennessee-Knoxville, USA.
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108
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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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109
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Sveshnikova N, Grimm R, Soll J, Schleiff E. Topology studies of the chloroplast protein import channel Toc75. Biol Chem 2000; 381:687-93. [PMID: 11030426 DOI: 10.1515/bc.2000.089] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A major goal in understanding protein transport across membranes is the investigation of the structure and regulation of the translocon subunits. We analysed Toc75, a pore-forming subunit of the translocon of the outer envelope of chloroplasts. Toc75 was overexpressed and reconstituted into liposomes. Immunoprecipitation of liposome-reconstituted Toc75 indicates an N(in)-C(in) orientation of Toc75. Limited proteolytic digestion of Toc75 present in outer envelope vesicles with specific proteases combined with amino acid sequencing was used to study the topology of Toc75. Finally, computer modelling based on known protein structures indicates that Toc75 traverses the outer envelope with 16 amphiphilic beta sheets and the topology model is presented.
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110
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Maier UG, Douglas SE, Cavalier-Smith T. The nucleo morph genomes of cryptophytes and chlorarachniophytes. Protist 2000; 151:103-9. [PMID: 10965950 DOI: 10.1078/1434-4610-00011] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- U G Maier
- Cell Biology and Applied Botany, Philipps-University Marburg, Germany.
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111
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Steinkamp T, Hill K, Hinnah SC, Wagner R, Röhl T, Pohlmeyer K, Soll J. Identification of the pore-forming region of the outer chloroplast envelope protein OEP16. J Biol Chem 2000; 275:11758-64. [PMID: 10766798 DOI: 10.1074/jbc.275.16.11758] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chloroplast outer envelope protein OEP16 forms a cation-selective high conductance channel with permeability to amines and amino acids. The region of OEP16 directly involved in channel formation has been identified by electrophysiological analysis of a selection of reconstituted OEP16 mutants. Because analysis of these mutants depended on the use of recombinant protein, we evaluated the electrophysiological properties of OEP16 isolated directly from pea chloroplasts and of the recombinant protein produced in Escherichia coli. The results show that the basic properties like conductance, selectivity, and open probability of the channel formed by native pea OEP16 are comparable with the channel activity formed by the recombinant source of the protein. Following electrophysiological analysis of OEP16 mutants we found that point mutations and insertion of additional amino acid residues in the region of the putative helix 1 (Glu(73) to Val(91)) did not change the properties of the OEP16 channel. The only exception was a Cys(71)-->Ser mutation, which led to a loss of the CuCl(2) sensitivity of the channel. Analysis of N- and C-terminal deletion mutants of OEP16 and mutants containing defined shuffled domains indicated that the minimal continuous region of OEP16, which is able to form a channel in liposomes, lies in the first half of the protein between amino acid residues 21 and 93.
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Affiliation(s)
- T Steinkamp
- Fachbereich Biologie/Chemie, Universität Osnabrück, D-49034 Osnabrück, Germany
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112
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Abstract
Membrane heredity was central to the unique symbiogenetic origin from cyanobacteria of chloroplasts in the ancestor of Plantae (green plants, red algae, glaucophytes) and to subsequent lateral transfers of plastids to form even more complex photosynthetic chimeras. Each symbiogenesis integrated disparate genomes and several radically different genetic membranes into a more complex cell. The common ancestor of Plantae evolved transit machinery for plastid protein import. In later secondary symbiogeneses, signal sequences were added to target proteins across host perialgal membranes: independently into green algal plastids (euglenoids, chlorarachneans) and red algal plastids (alveolates, chromists). Conservatism and innovation during early plastid diversification are discussed.
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113
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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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114
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Abstract
Three proteins from the chloroplastic outer envelope membrane and four proteins from the inner envelope membrane have been identified as components of the chloroplastic protein import apparatus. Multiple molecular chaperones and a stromal processing peptidase are also important components of the import machinery. The interactions of these proteins with each other and with the precursors destined for transport into chloroplasts are gradually being described using both biochemical and genetic strategies. Homologs of some transport components have been identified in cyanobacteria suggesting that at least some of import machinery was inherited from the cyanobacterial ancestors that gave rise to chloroplasts.
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Affiliation(s)
- K Keegstra
- MSU-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824-1312, USA.
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115
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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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116
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Delwiche CF. Tracing the Thread of Plastid Diversity through the Tapestry of Life. Am Nat 1999; 154:S164-S177. [PMID: 10527925 DOI: 10.1086/303291] [Citation(s) in RCA: 203] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Plastids (chloroplasts) are endosymbiotic organelles derived from previously free-living cyanobacteria. They are dependent on their host cell to the degree that the majority of the proteins expressed in the plastid are encoded in the nuclear genome of the host cell, and it is this genetic dependency that distinguishes organelles from obligate endosymbionts. Reduction in the size of the plastid genome has occurred via gene loss, substitution of nuclear genes, and gene transfer. The plastids of Chlorophyta and plants, Rhodophyta, and Glaucocystophyta are primary plastids (i.e., derived directly from a cyanobacterium). These three lineages may or may not be descended from a single endosymbiotic event. All other lineages of plastids have acquired their plastids by secondary (or tertiary) endosymbiosis, in which a eukaryote already equipped with plastids is preyed upon by a second eukaryote. Considerable gene transfer has occurred among genomes and, at times, between organisms. The eukaryotic crown group Alveolata has a particularly complex history of plastid acquisition.
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117
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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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118
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Abstract
Chloroplasts are believed to have originated from a photosynthetic, prokaryotic ancestor. As the result of endosymbiotic evolution, most of the genes of the endocytobiont were displaced to the host nucleus. Today's chloroplasts must import most of their proteins from the cytosol as precursors. Oligomeric protein complexes in the chloroplast outer and inner envelope membranes are responsible for the specific recognition and membrane translocation of precursor proteins. The translocon at the outer membrane of chloroplasts and the inner membrane of chloroplasts act jointly during the import process. Several translocon subunits have been partially characterized in their molecular structure and function. Initial evidence indicates the prokaryotic origin of some chloroplast translocon components.
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Affiliation(s)
- T May
- Botanisches Institut der Universität Kiel, Germany
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119
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Abstract
Chloroplasts have evolved an elaborate system of membrane and soluble subcompartments to organize and regulate photosynthesis and essential aspects of amino acid and lipid metabolism. The biogenesis and maintenance of organellar architecture rely on protein subunits encoded by both nuclear and plastid genomes. Import of nuclear-encoded proteins is mediated by interactions between the intrinsic N-terminal transit sequence of the nuclear-encoded preprotein and a common import machinery at the chloroplast envelope. Recent investigations have shown that there are two unique membrane-bound translocation systems, in the outer and inner envelope membranes, which physically associate during import to transport preproteins from the cytoplasm to the internal stromal compartment. This review discusses current understanding of these translocation systems and models for the way in which they might function.
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Affiliation(s)
- X Chen
- Dept of Biological Sciences, Rutgers, The State University of New Jersey, 101 Warren Street, Newark, NJ 07102, USA
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120
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Affiliation(s)
- A Caliebe
- Botanisches Institut, Christian-Albrechts-Universität Kiel, Germany
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121
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Reumann S, Davila-Aponte J, Keegstra K. The evolutionary origin of the protein-translocating channel of chloroplastic envelope membranes: identification of a cyanobacterial homolog. Proc Natl Acad Sci U S A 1999; 96:784-9. [PMID: 9892711 PMCID: PMC15214 DOI: 10.1073/pnas.96.2.784] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/1998] [Indexed: 11/18/2022] Open
Abstract
The known envelope membrane proteins of the chloroplastic protein import apparatus lack sequence similarity to proteins of other eukaryotic or prokaryotic protein transport systems. However, we detected a putative homolog of the gene encoding Toc75, the protein-translocating channel from the outer envelope membrane of pea chloroplasts, in the genome of the cyanobacterium Synechocystis sp. PCC 6803. We investigated whether the low sequence identity of 21% reflects a structural and functional relationship between the two proteins. We provide evidence that the cyanobacterial protein is also localized in the outer membrane. From this information and the similarity of the predicted secondary structures, we conclude that Toc75 and the cyanobacterial protein, referred to as SynToc75, are structural homologs. synToc75 is essential, as homozygous null mutants were not recovered after directed mutagenesis. Sequence analysis indicates that SynToc75 belongs to a family of outer membrane proteins from Gram-negative bacteria whose function is not yet known. However, we demonstrate that these proteins are related to a specific group of prokaryotic secretion channels that transfer virulence factors, such as hemolysins and adhesins, across the outer membrane.
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Affiliation(s)
- S Reumann
- Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824-1312, USA
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