1
|
Ballabani G, Forough M, Kessler F, Shanmugabalaji V. The journey of preproteins across the chloroplast membrane systems. Front Physiol 2023; 14:1213866. [PMID: 37324391 PMCID: PMC10267391 DOI: 10.3389/fphys.2023.1213866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
The photosynthetic capacity of chloroplasts is vital for autotrophic growth in algae and plants. The origin of the chloroplast has been explained by the endosymbiotic theory that proposes the engulfment of a cyanobacterium by an ancestral eukaryotic cell followed by the transfer of many cyanobacterial genes to the host nucleus. As a result of the gene transfer, the now nuclear-encoded proteins acquired chloroplast targeting peptides (known as transit peptides; transit peptide) and are translated as preproteins in the cytosol. Transit peptides contain specific motifs and domains initially recognized by cytosolic factors followed by the chloroplast import components at the outer and inner envelope of the chloroplast membrane. Once the preprotein emerges on the stromal side of the chloroplast protein import machinery, the transit peptide is cleaved by stromal processing peptidase. In the case of thylakoid-localized proteins, cleavage of the transit peptides may expose a second targeting signal guiding the protein to the thylakoid lumen or allow insertion into the thylakoid membrane by internal sequence information. This review summarizes the common features of targeting sequences and describes their role in routing preproteins to and across the chloroplast envelope as well as the thylakoid membrane and lumen.
Collapse
Affiliation(s)
| | | | - Felix Kessler
- *Correspondence: Felix Kessler, ; Venkatasalam Shanmugabalaji,
| | | |
Collapse
|
2
|
Protein Markers for the Identification of Cork Oak Plants Infected with Phytophthora cinnamomi by Applying an (α, β)-k-Feature Set Approach. FORESTS 2022. [DOI: 10.3390/f13060940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cork oak decline in Mediterranean forests is a complex phenomenon, observed with remarkable frequency in the southern part of the Iberian Peninsula, causing the weakening and death of these woody plants. The defoliation of the canopy, the presence of dry peripheral branches, and exudations on the trunk are visible symptoms used for the prognosis of decline, complemented by the presence of Phytophthora cinnamomi identified in the rhizosphere of the trees and adjacent soils. Recently, a large proteomic dataset obtained from the leaves of cork oak plants inoculated and non-inoculated with P. cinnamomi has become available. We explored it to search for an optimal set of proteins, markers of the biological pattern of interaction with the oomycete. Thus, using published data from the cork oak leaf proteome, we mathematically modelled the problem as an α, β-k-Feature Set Problem to select molecular markers. A set of proteins (features) that represent dominant effects on the host metabolism resulting from pathogen action on roots was found. These results contribute to an early diagnosis of biochemical changes occurring in cork oak associated with P. cinnamomi infection. We hypothesize that these markers may be decisive in identifying trees that go into decline due to interactions with the pathogen, assisting the management of cork oak forest ecosystems.
Collapse
|
3
|
Kulichová K, Pieters J, Kumar V, Honys D, Hafidh S. A Plastid-Bound Ankyrin Repeat Protein Controls Gametophyte and Early Embryo Development in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2022; 13:767339. [PMID: 35350296 PMCID: PMC8958021 DOI: 10.3389/fpls.2022.767339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Proplastids are essential precursors for multi-fate plastid biogenesis, including chloroplast differentiation, a powerhouse for photosynthesis in plants. Arabidopsis ankyrin repeat protein (AKRP, AT5G66055) is a plastid-localized protein with a putative function in plastid differentiation and morphogenesis. Loss of function of akrp leads to embryo developmental arrest. Whether AKRP is critical pre-fertilization has remained unresolved. Here, using reverse genetics, we report a new allele, akrp-3, that exhibited a reduced frequency of mutant embryos (<13%) compared to previously reported alleles. akrp-3 affected both male and female gametophytes resulting in reduced viability, incompetence in pollen tube attraction, altered gametic cell fate, and embryo arrest that were depleted of chlorophyll. AKRP is widely expressed, and the AKRP-GFP fusion localized to plastids of both gametophytes, in isolated chloroplast and co-localized with a plastid marker in pollen and pollen tubes. Cell-type-specific complementation of akrp-3 hinted at the developmental timing at which AKRP might play an essential role. Our findings provide a plausible insight into the crucial role of AKRP in the differentiation of both gametophytes and coupling embryo development with chlorophyll synthesis.
Collapse
Affiliation(s)
- Katarína Kulichová
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czechia
| | - Janto Pieters
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czechia
| | - Vinod Kumar
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czechia
| | - David Honys
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czechia
- Department of Plant Experimental Biology, Faculty of Science, Charles University, Prague, Czechia
| | - Said Hafidh
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
4
|
Jiang T, Mu B, Zhao R. Plastid chaperone HSP90C guides precursor proteins to the SEC translocase for thylakoid transport. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:7073-7087. [PMID: 32853383 PMCID: PMC7906790 DOI: 10.1093/jxb/eraa399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 08/24/2020] [Indexed: 05/04/2023]
Abstract
Chloroplast stromal factors involved in regulating thylakoid protein targeting are poorly understood. We previously reported that in Arabidopsis thaliana, the stromal-localized chaperone HSP90C (plastid heat shock protein 90) interacted with the nuclear-encoded thylakoid lumen protein PsbO1 (PSII subunit O isoform 1) and suggested a role for HSP90C in aiding PsbO1 thylakoid targeting. Using in organello transport assays, particularly with model substrates naturally expressed in stroma, we showed that light, exogenous ATP, and HSP90C activity were required for Sec-dependent transport of green fluorescent protein (GFP) led by the PsbO1 thylakoid targeting sequence. Using a previously identified PsbO1T200A mutant, we provided evidence that a stronger interaction between HSP90C and PsbO1 better facilitated its stroma-thylakoid trafficking. We also demonstrated that SecY1, the channel protein of the thylakoid SEC translocase, specifically interacted with HSP90C in vivo. Inhibition of the chaperone ATPase activity suppressed the association of the PsbO1GFP-HSP90C complex with SecY1. Together with analyzing the expression and accumulation of a few other thylakoid proteins that utilize the SRP, TAT, or SEC translocation pathways, we propose a model in which HSP90C forms a guiding complex that interacts with thylakoid protein precursors and assists in their specific targeting to the thylakoid SEC translocon.
Collapse
Affiliation(s)
- Tim Jiang
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Bona Mu
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Rongmin Zhao
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Correspondence:
| |
Collapse
|
5
|
Ouyang M, Li X, Zhang J, Feng P, Pu H, Kong L, Bai Z, Rong L, Xu X, Chi W, Wang Q, Chen F, Lu C, Shen J, Zhang L. Liquid-Liquid Phase Transition Drives Intra-chloroplast Cargo Sorting. Cell 2020; 180:1144-1159.e20. [PMID: 32169217 DOI: 10.1016/j.cell.2020.02.045] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 01/14/2020] [Accepted: 02/20/2020] [Indexed: 12/21/2022]
Abstract
In eukaryotic cells, organelle biogenesis is pivotal for cellular function and cell survival. Chloroplasts are unique organelles with a complex internal membrane network. The mechanisms of the migration of imported nuclear-encoded chloroplast proteins across the crowded stroma to thylakoid membranes are less understood. Here, we identified two Arabidopsis ankyrin-repeat proteins, STT1 and STT2, that specifically mediate sorting of chloroplast twin arginine translocation (cpTat) pathway proteins to thylakoid membranes. STT1 and STT2 form a unique hetero-dimer through interaction of their C-terminal ankyrin domains. Binding of cpTat substrate by N-terminal intrinsically disordered regions of STT complex induces liquid-liquid phase separation. The multivalent nature of STT oligomer is critical for phase separation. STT-Hcf106 interactions reverse phase separation and facilitate cargo targeting and translocation across thylakoid membranes. Thus, the formation of phase-separated droplets emerges as a novel mechanism of intra-chloroplast cargo sorting. Our findings highlight a conserved mechanism of phase separation in regulating organelle biogenesis.
Collapse
Affiliation(s)
- Min Ouyang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Xiaoyi Li
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jing Zhang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing, China
| | - Peiqiang Feng
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Hua Pu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Lingxi Kong
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing, China
| | - Zechen Bai
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing, China
| | - Liwei Rong
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xiumei Xu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, 85 Minglun Street, Kaifeng 475001, China
| | - Wei Chi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing, China
| | - Qiang Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, 85 Minglun Street, Kaifeng 475001, China
| | - Fan Chen
- State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Beijing 100086, China
| | - Congming Lu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, China
| | - Jianren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Lixin Zhang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, 85 Minglun Street, Kaifeng 475001, China.
| |
Collapse
|
6
|
Theg SM. Chloroplast transport and import. PHOTOSYNTHESIS RESEARCH 2018; 138:261-262. [PMID: 30397741 DOI: 10.1007/s11120-018-0593-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 10/03/2018] [Indexed: 06/08/2023]
Affiliation(s)
- Steven M Theg
- Department of Plant Biology, University of California, Davis, Davis, CA, 95616, USA.
| |
Collapse
|
7
|
Day PM, Theg SM. Evolution of protein transport to the chloroplast envelope membranes. PHOTOSYNTHESIS RESEARCH 2018; 138:315-326. [PMID: 30291507 DOI: 10.1007/s11120-018-0540-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/20/2018] [Indexed: 05/11/2023]
Abstract
Chloroplasts are descendants of an ancient endosymbiotic cyanobacterium that lived inside a eukaryotic cell. They inherited the prokaryotic double membrane envelope from cyanobacteria. This envelope contains prokaryotic protein sorting machineries including a Sec translocase and relatives of the central component of the bacterial outer membrane β-barrel assembly module. As the endosymbiont was integrated with the rest of the cell, the synthesis of most of its proteins shifted from the stroma to the host cytosol. This included nearly all the envelope proteins identified so far. Consequently, the overall biogenesis of the chloroplast envelope must be distinct from cyanobacteria. Envelope proteins initially approach their functional locations from the exterior rather than the interior. In many cases, they have been shown to use components of the general import pathway that also serves the stroma and thylakoids. If the ancient prokaryotic protein sorting machineries are still used for chloroplast envelope proteins, their activities must have been modified or combined with the general import pathway. In this review, we analyze the current knowledge pertaining to chloroplast envelope biogenesis and compare this to bacteria.
Collapse
Affiliation(s)
- Philip M Day
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA
| | - Steven M Theg
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA.
| |
Collapse
|
8
|
Fernandez DE. Two paths diverged in the stroma: targeting to dual SEC translocase systems in chloroplasts. PHOTOSYNTHESIS RESEARCH 2018; 138:277-287. [PMID: 29951837 DOI: 10.1007/s11120-018-0541-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
Chloroplasts inherited systems and strategies for protein targeting, translocation, and integration from their cyanobacterial ancestor. Unlike cyanobacteria however, chloroplasts in green algae and plants contain two distinct SEC translocase/integrase systems: the SEC1 system in the thylakoid membrane and the SEC2 system in the inner envelope membrane. This review summarizes the mode of action of SEC translocases, identification of components of the SEC2 system, evolutionary history of SCY and SECA genes, and previous work on the co- and post-translational targeting of lumenal and thylakoid membrane proteins to the SEC1 system. Recent work identifying substrates for the SEC2 system and potential features that may contribute to inner envelope targeting are also discussed.
Collapse
Affiliation(s)
- Donna E Fernandez
- Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
| |
Collapse
|
9
|
Asher A, Ganesan I, Klasek L, Theg SM. Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays. J Vis Exp 2018:58393. [PMID: 30320750 PMCID: PMC6235370 DOI: 10.3791/58393] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Chloroplasts are the organelles in green plants responsible for carrying out numerous essential metabolic pathways, most notably photosynthesis. Within the chloroplasts, the thylakoid membrane system houses all the photosynthetic pigments, reaction center complexes, and most of the electron carriers, and is responsible for light-dependent ATP synthesis. Over 90% of chloroplast proteins are encoded in the nucleus, translated in the cytosol, and subsequently imported into the chloroplast. Further protein transport into or across the thylakoid membrane utilizes one of four translocation pathways. Here, we describe a high-yield method for isolation of transport-competent thylakoids from peas (Pisum sativum), along with transport assays through the three energy-dependent cpTat, cpSec1, and cpSRP-mediated pathways. These methods enable experiments relating to thylakoid protein localization, transport energetics, and the mechanisms of protein translocation across biological membranes.
Collapse
Affiliation(s)
- Anthony Asher
- Department of Plant Biology, University of California - Davis
| | - Iniyan Ganesan
- Department of Plant Biology, University of California - Davis
| | - Laura Klasek
- Department of Plant Biology, University of California - Davis
| | - Steven M Theg
- Department of Plant Biology, University of California - Davis;
| |
Collapse
|
10
|
Jiang T, Oh ES, Bonea D, Zhao R. HSP90C interacts with PsbO1 and facilitates its thylakoid distribution from chloroplast stroma in Arabidopsis. PLoS One 2017; 12:e0190168. [PMID: 29281724 PMCID: PMC5745004 DOI: 10.1371/journal.pone.0190168] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/08/2017] [Indexed: 11/29/2022] Open
Abstract
Arabidopsis plastidic HSP90C is an HSP90 family molecular chaperone that is required for chloroplast development and function. To understand the mechanism of action of HSP90C within the chloroplast, we conducted a yeast two-hybrid screening and revealed it interacts directly with the photosystem II extrinsic protein PsbO1, which performs a canonical function in the thylakoid lumen. To understand the biological significance of HSP90C-PsbO1 interaction, we investigated the role of HSP90C in modulating the stromal and thylakoid distribution of PsbO1GFP fusion protein. Fusion to GFP significantly delays the PsbO1 thylakoid transport and induces a variegation phenotype. Overexpression of HSP90C promotes the thylakoid distribution of PsbO1GFP and alleviates the leaf variegation. By tracking the chloroplast maturation during photomorphogenesis, we observed PsbO1GFP tends to form distinct fluorescent clusters within the stroma with delayed thylakoid membrane biogenesis, while HSP90C overexpression corrects these adverse effects. We also demonstrated that active HSP90C function is specifically required for stable accumulation of mature PsbO1GFP in thylakoid by using specific inhibitor geldanamycin. This study therefore not only identified novel HSP90C interactors, but also reports for the first time that PsbO1 enroute from the cytoplasm to thylakoid lumen is tightly regulated by the HSP90C chaperone complex in plastid stroma; whereas the proper HSP90C homeostasis is also critical for chloroplast maturation and function.
Collapse
Affiliation(s)
- Tim Jiang
- Departments of Biological Sciences and Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Edward Saehong Oh
- Departments of Biological Sciences and Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Diana Bonea
- Departments of Biological Sciences and Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Rongmin Zhao
- Departments of Biological Sciences and Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
| |
Collapse
|
11
|
Li Y, Singhal R, Taylor IW, McMinn PH, Chua XY, Cline K, Fernandez DE. The Sec2 translocase of the chloroplast inner envelope contains a unique and dedicated SECE2 component. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 84:647-658. [PMID: 26406904 DOI: 10.1111/tpj.13028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 08/28/2015] [Accepted: 09/03/2015] [Indexed: 06/05/2023]
Abstract
Biogenesis of chloroplasts involves a series of protein trafficking events. Nuclear-encoded proteins are imported into the organelle, and then trafficked to various chloroplast locations by systems that are directly homologous to bacterial systems. Although the thylakoid-based systems have been studied extensively, much less is known about the systems that reside and function in the inner envelope membrane. One such system, the Sec2 system, is homologous to both the thylakoid-based Sec1 system and bacterial Sec systems, and may mediate both integration and translocation across the inner envelope. At a minimum, this system is expected to include three components, but only two, SCY2 and SECA2, have been identified in Arabidopsis. Bioinformatics and protein modeling were used to identify the protein encoded by At4g38490 as a candidate for the missing component (SECE2). Cellular localization, biochemistry, protein interaction assays in yeast, and co-immunoprecipitation experiments were used to establish that this protein is an integral membrane protein of the inner envelope, and specifically interacts with the SCY2 component in vivo. Sequence analyses indicated that SECE2 proteins are found in a variety of plants, and differ from the thylakoid SECE1 proteins in a stroma-exposed helical domain, which may contribute to their specificity. Finally, a genetic analysis indicated that SECE2 plays an essential role in plant growth and development.
Collapse
Affiliation(s)
- Yubing Li
- Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Rajneesh Singhal
- Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA
| | - Isaiah W Taylor
- Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA
| | - Patrick H McMinn
- Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA
| | - Xien Yu Chua
- Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA
| | - Kenneth Cline
- Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Donna E Fernandez
- Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA
| |
Collapse
|
12
|
Endow JK, Singhal R, Fernandez DE, Inoue K. Chaperone-assisted Post-translational Transport of Plastidic Type I Signal Peptidase 1. J Biol Chem 2015; 290:28778-91. [PMID: 26446787 DOI: 10.1074/jbc.m115.684829] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Indexed: 01/19/2023] Open
Abstract
Type I signal peptidase (SPase I) is an integral membrane Ser/Lys protease with one or two transmembrane domains (TMDs), cleaving transport signals off translocated precursor proteins. The catalytic domain of SPase I folds to form a hydrophobic surface and inserts into the lipid bilayers at the trans-side of the membrane. In bacteria, SPase I is targeted co-translationally, and the catalytic domain remains unfolded until it reaches the periplasm. By contrast, SPases I in eukaryotes are targeted post-translationally, requiring an alternative strategy to prevent premature folding. Here we demonstrate that two distinct stromal components are involved in post-translational transport of plastidic SPase I 1 (Plsp1) from Arabidopsis thaliana, which contains a single TMD. During import into isolated chloroplasts, Plsp1 was targeted to the membrane via a soluble intermediate in an ATP hydrolysis-dependent manner. Insertion of Plsp1 into isolated chloroplast membranes, by contrast, was found to occur by two distinct mechanisms. The first mechanism requires ATP hydrolysis and the protein conducting channel cpSecY1 and was strongly enhanced by exogenously added cpSecA1. The second mechanism was independent of nucleoside triphosphates and proteinaceous components but with a high frequency of mis-orientation. This unassisted insertion was inhibited by urea and stroma extract. During import-chase assays using intact chloroplasts, Plsp1 was incorporated into a soluble 700-kDa complex that co-migrated with the Cpn60 complex before inserting into the membrane. The TMD within Plsp1 was required for the cpSecA1-dependent insertion but was dispensable for association with the 700-kDa complex and also for unassisted membrane insertion. These results indicate cooperation of Cpn60 and cpSecA1 for proper membrane insertion of Plsp1 by cpSecY1.
Collapse
Affiliation(s)
- Joshua K Endow
- From the Department of Plant Sciences, University of California, Davis, California 95616 and
| | - Rajneesh Singhal
- the Department of Botany, University of Wisconsin, Madison, Wisconsin 53706
| | - Donna E Fernandez
- the Department of Botany, University of Wisconsin, Madison, Wisconsin 53706
| | - Kentaro Inoue
- From the Department of Plant Sciences, University of California, Davis, California 95616 and
| |
Collapse
|
13
|
Dittmar J, Schlesier R, Klösgen RB. Tat transport of a Sec passenger leads to both completely translocated as well as membrane-arrested passenger proteins. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:446-53. [PMID: 24321767 DOI: 10.1016/j.bbamcr.2013.11.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/26/2013] [Accepted: 11/29/2013] [Indexed: 11/26/2022]
Abstract
We have studied the membrane transport of the chimeric precursor protein 16/33, which is composed of the Tat(1)-specific transport signal of OEC16 and the Sec passenger protein OEC33, both subunits of the oxygen-evolving system associated with photosystem II. Protein transport experiments performed with isolated pea thylakoids show that the 16/33 chimera is transported in a strictly Tat-dependent manner into the thylakoid vesicles yielding mature OEC33 (mOEC33) in two different topologies. One fraction accumulates in the thylakoid lumen and is thus resistant to externally added protease. A second fraction is arrested during transport in an N-in/C-out topology within the membrane. Chase experiments demonstrate that this membrane-arrested mOEC33 moiety does not represent a translocation intermediate but instead an alternative end product of the transport process. Transport arrest of mOEC33, which is embedded in the membrane with a mildly hydrophobic protein segment, requires more than 26 additional and predominantly hydrophilic residues C-terminal of the membrane-embedded segment. Furthermore, it is stimulated by mutations which potentially affect the conformation of mOEC33 suggesting that at least partial folding of the passenger protein is required for complete membrane translocation.
Collapse
Affiliation(s)
- Julia Dittmar
- Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany
| | - René Schlesier
- Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany
| | - Ralf Bernd Klösgen
- Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany.
| |
Collapse
|
14
|
Järvi S, Gollan PJ, Aro EM. Understanding the roles of the thylakoid lumen in photosynthesis regulation. FRONTIERS IN PLANT SCIENCE 2013; 4:434. [PMID: 24198822 PMCID: PMC3813922 DOI: 10.3389/fpls.2013.00434] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/12/2013] [Indexed: 05/20/2023]
Abstract
It has been known for a long time that the thylakoid lumen provides the environment for oxygen evolution, plastocyanin-mediated electron transfer, and photoprotection. More recently lumenal proteins have been revealed to play roles in numerous processes, most often linked with regulating thylakoid biogenesis and the activity and turnover of photosynthetic protein complexes, especially the photosystem II and NAD(P)H dehydrogenase-like complexes. Still, the functions of the majority of lumenal proteins in Arabidopsis thaliana are unknown. Interestingly, while the thylakoid lumen proteome of at least 80 proteins contains several large protein families, individual members of many protein families have highly divergent roles. This is indicative of evolutionary pressure leading to neofunctionalization of lumenal proteins, emphasizing the important role of the thylakoid lumen for photosynthetic electron transfer and ultimately for plant fitness. Furthermore, the involvement of anterograde and retrograde signaling networks that regulate the expression and activity of lumen proteins is increasingly pertinent. Recent studies have also highlighted the importance of thiol/disulfide modulation in controlling the functions of many lumenal proteins and photosynthetic regulation pathways.
Collapse
Affiliation(s)
| | | | - Eva-Mari Aro
- *Correspondence: Eva-Mari Aro, Molecular Plant Biology, Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland e-mail:
| |
Collapse
|
15
|
Celedon JM, Cline K. Intra-plastid protein trafficking: how plant cells adapted prokaryotic mechanisms to the eukaryotic condition. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:341-51. [PMID: 22750312 DOI: 10.1016/j.bbamcr.2012.06.028] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/11/2012] [Accepted: 06/20/2012] [Indexed: 12/14/2022]
Abstract
Protein trafficking and localization in plastids involve a complex interplay between ancient (prokaryotic) and novel (eukaryotic) translocases and targeting machineries. During evolution, ancient systems acquired new functions and novel translocation machineries were developed to facilitate the correct localization of nuclear encoded proteins targeted to the chloroplast. Because of its post-translational nature, targeting and integration of membrane proteins posed the biggest challenge to the organelle to avoid aggregation in the aqueous compartments. Soluble proteins faced a different kind of problem since some had to be transported across three membranes to reach their destination. Early studies suggested that chloroplasts addressed these issues by adapting ancient-prokaryotic machineries and integrating them with novel-eukaryotic systems, a process called 'conservative sorting'. In the last decade, detailed biochemical, genetic, and structural studies have unraveled the mechanisms of protein targeting and localization in chloroplasts, suggesting a highly integrated scheme where ancient and novel systems collaborate at different stages of the process. In this review we focus on the differences and similarities between chloroplast ancestral translocases and their prokaryotic relatives to highlight known modifications that adapted them to the eukaryotic situation. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
Collapse
Affiliation(s)
- Jose M Celedon
- Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL 32611, USA
| | | |
Collapse
|
16
|
Albiniak AM, Baglieri J, Robinson C. Targeting of lumenal proteins across the thylakoid membrane. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1689-98. [PMID: 22275386 DOI: 10.1093/jxb/err444] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The biogenesis of the plant thylakoid network is an enormously complex process in terms of protein targeting. The membrane system contains a large number of proteins, some of which are synthesized within the organelle, while many others are imported from the cytosol. Studies in recent years have shown that the targeting of imported proteins into and across the thylakoid membrane is particularly complex, with four different targeting pathways identified to date. Two of these are used to target membrane proteins: a signal recognition particle (SRP)-dependent pathway and a highly unusual pathway that appears to require none of the known targeting apparatus. Two further pathways are used to translocate lumenal proteins across the thylakoid membrane from the stroma and, again, the two pathways differ dramatically from each other. One is a Sec-type pathway, in which ATP hydrolysis by SecA drives the transport of the substrate protein through the membrane in an unfolded conformation. The other is the twin-arginine translocation (Tat) pathway, where substrate proteins are transported in a folded state using a unique mechanism that harnesses the proton motive force across the thylakoid membrane. This article reviews progress in studies on the targeting of lumenal proteins, with reference to the mechanisms involved, their evolution from endosymbiotic progenitors of the chloroplast, and possible elements of regulation.
Collapse
Affiliation(s)
- Anna M Albiniak
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
| | | | | |
Collapse
|
17
|
Skalitzky CA, Martin JR, Harwood JH, Beirne JJ, Adamczyk BJ, Heck GR, Cline K, Fernandez DE. Plastids contain a second sec translocase system with essential functions. PLANT PHYSIOLOGY 2011; 155:354-69. [PMID: 21051552 PMCID: PMC3075773 DOI: 10.1104/pp.110.166546] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 11/04/2010] [Indexed: 05/20/2023]
Abstract
Proteins that are synthesized on cytoplasmic ribosomes but function within plastids must be imported and then targeted to one of six plastid locations. Although multiple systems that target proteins to the thylakoid membranes or thylakoid lumen have been identified, a system that can direct the integration of inner envelope membrane proteins from the stroma has not been previously described. Genetics and localization studies were used to show that plastids contain two different Sec systems with distinct functions. Loss-of-function mutations in components of the previously described thylakoid-localized Sec system, designated as SCY1 (At2g18710), SECA1 (At4g01800), and SECE1 (At4g14870) in Arabidopsis (Arabidopsis thaliana), result in albino seedlings and sucrose-dependent heterotrophic growth. Loss-of-function mutations in components of the second Sec system, designated as SCY2 (At2g31530) and SECA2 (At1g21650) in Arabidopsis, result in arrest at the globular stage and embryo lethality. Promoter-swap experiments provided evidence that SCY1 and SCY2 are functionally nonredundant and perform different roles in the cell. Finally, chloroplast import and fractionation assays and immunogold localization of SCY2-green fluorescent protein fusion proteins in root tissues indicated that SCY2 is part of an envelope-localized Sec system. Our data suggest that SCY2 and SECA2 function in Sec-mediated integration and translocation processes at the inner envelope membrane.
Collapse
|
18
|
In silico methods for identifying organellar and suborganellar targeting peptides in Arabidopsis chloroplast proteins and for predicting the topology of membrane proteins. Methods Mol Biol 2011; 774:243-80. [PMID: 21822844 DOI: 10.1007/978-1-61779-234-2_16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Numerous experimental and in silico approaches have been developed for attempting to identify the -subcellular localisation of proteins. Approximately 2,000-4,000 proteins are thought to be targeted to plastids in plants, but a complete and unambiguous catalogue has yet to be drawn up. This article reviews the various prediction methods that identify plastid targeting sequences, and those that can help estimate location and topology within the plastid or plastid membranes. The most successful approaches are described in detail, with detailed notes to help avoid common pitfalls and advice on interpreting conflicting or ambiguous results. In most cases, it is best to try multiple approaches, and we also cover the powerful new integrated databases that provide a selected blend of experimental data and predictions.
Collapse
|
19
|
Liu D, Gong Q, Ma Y, Li P, Li J, Yang S, Yuan L, Yu Y, Pan D, Xu F, Wang NN. cpSecA, a thylakoid protein translocase subunit, is essential for photosynthetic development in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1655-69. [PMID: 20194926 DOI: 10.1093/jxb/erq033] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The endosymbiont-derived Sec-dependent protein sorting pathway is essential for protein import into the thylakoid lumen and is important for the proper functioning of the chloroplast. Two loss-of-function mutants of cpSecA, the ATPase subunit of the chloroplast Sec translocation machinery, were analysed in Arabidopsis. The homozygous mutants were albino and seedling lethal under autotrophic conditions and remained dwarf and infertile with an exogenous carbon supply. They were subject to oxidative stress and accumulated superoxide under normal lighting conditions. Electron microscopy revealed that the chloroplast of the mutants had underdeveloped thylakoid structures. Histochemical GUS assay of the AtcpSecA::GUS transgenic plants confirmed that AtcpSecA was expressed in green organs in a light-inducible way. Real-time RT-PCR and microarray analysis revealed repressed transcription of nucleus- and chloroplast- encoded subunits of photosynthetic complexes, and induced transcription of chloroplast protein translocation machinery and mitochondrion-encoded respiratory complexes in the mutants. It is inferred that AtcpSecA plays an essential role in chloroplast biogenesis, the absence of which triggered a retrograde signal, eventually leading to a reprogramming of chloroplast and mitochondrial gene expression.
Collapse
MESH Headings
- Arabidopsis/genetics
- Arabidopsis/metabolism
- Arabidopsis/physiology
- Arabidopsis/ultrastructure
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Chloroplast Proteins
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation, Plant/genetics
- Gene Expression Regulation, Plant/physiology
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Oligonucleotide Array Sequence Analysis
- Oxidative Stress/genetics
- Oxidative Stress/physiology
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/metabolism
- Plants, Genetically Modified/physiology
- Plants, Genetically Modified/ultrastructure
- Protein Subunits/genetics
- Protein Subunits/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Thylakoids/enzymology
- Thylakoids/ultrastructure
Collapse
Affiliation(s)
- Dong Liu
- Department of Plant Biology and Ecology, Nankai University, Tianjin 300071, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Aldridge C, Cain P, Robinson C. Protein transport in organelles: Protein transport into and across the thylakoid membrane. FEBS J 2009; 276:1177-86. [PMID: 19187234 DOI: 10.1111/j.1742-4658.2009.06875.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The chloroplast thylakoid is the most abundant membrane system in nature, and is responsible for the critical processes of light capture, electron transport and photophosphorylation. Most of the resident proteins are imported from the cytosol and then transported into or across the thylakoid membrane. This minireview describes the multitude of pathways used for these proteins. We discuss the huge differences in the mechanisms involved in the secretory and twin-arginine translocase pathways used for the transport of proteins into the lumen, with an emphasis on the differing substrate conformations and energy requirements. We also discuss the rationale for the use of two different systems for membrane protein insertion: the signal recognition particle pathway and the so-called spontaneous pathway. The recent crystallization of a key chloroplast signal recognition particle component provides new insights into this rather unique form of signal recognition particle.
Collapse
Affiliation(s)
- Cassie Aldridge
- Department of Biological Sciences, University of Warwick, Coventry, UK
| | | | | |
Collapse
|
21
|
Yusa F, Steiner JM, Löffelhardt W. Evolutionary conservation of dual Sec translocases in the cyanelles of Cyanophora paradoxa. BMC Evol Biol 2008; 8:304. [PMID: 18976493 PMCID: PMC2600650 DOI: 10.1186/1471-2148-8-304] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 11/01/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cyanelles, the peptidoglycan-armored plastids of glaucocystophytes, occupy a unique bridge position in between free-living cyanobacteria and chloroplasts. In some respects they side with cyanobacteria whereas other features are clearly shared with chloroplasts. The Sec translocase, an example for "conservative sorting" in the course of evolution, is found in the plasma membrane of all prokaryotes, in the thylakoid membrane of chloroplasts and in both these membrane types of cyanobacteria. RESULTS In this paper we present evidence for a dual location of the Sec translocon in the thylakoid as well as inner envelope membranes of the cyanelles from Cyanophora paradoxa, i. e. conservative sorting sensu stricto. The prerequisite was the generation of specific antisera directed against cyanelle SecY that allowed immunodetection of the protein on SDS gels from both membrane types separated by sucrose density gradient floatation centrifugation. Immunoblotting of blue-native gels yielded positive but differential results for both the thylakoid and envelope Sec complexes, respectively. In addition, heterologous antisera directed against components of the Toc/Tic translocons and binding of a labeled precursor protein were used to discriminate between inner and outer envelope membranes. CONCLUSION The envelope translocase can be envisaged as a prokaryotic feature missing in higher plant chloroplasts but retained in cyanelles, likely for protein transport to the periplasm. Candidate passengers are cytochrome c6 and enzymes of peptidoglycan metabolism. The minimal set of subunits of the Toc/Tic translocase of a primitive plastid is proposed.
Collapse
Affiliation(s)
- Fumie Yusa
- SLT, Nagahama-city, Shiga-ken 526-0829, Japan.
| | | | | |
Collapse
|
22
|
Koussevitzky S, Ne'eman E, Peleg S, Harel E. Polyphenol oxidase can cross thylakoids by both the Tat and the Sec-dependent pathways: a putative role for two stromal processing sites. PHYSIOLOGIA PLANTARUM 2008; 133:266-77. [PMID: 18331405 DOI: 10.1111/j.1399-3054.2008.01074.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Polyphenol oxidase (PPO; EC 1.10.3.2 or EC 1.14.18.1), a thylakoid-lumen protein encoded by a nuclear gene, plays a role in the defense of plants against both herbivores and pathogens. Although previously reported to be a Tat (twin-arginine-dependent translocation) protein, the import of PPO by isolated chloroplasts was inhibited by azide, a diagnostic inhibitor of the Sec-dependent pathway. Import of PPO inhibited thylakoid translocation of a Tat protein and did not affect translocation of Sec-dependent proteins. In contrast, a pre-accumulated iPPO competed with Sec-dependent but not with Tat proteins. A previously reported second processing step in the stroma removes a twin-Arg that is part of a 'Sec-avoidance' motif in the thylakoid targeting domain of PPO. When the second processing site was mutated, the import of the resulting precursor showed Sec-dependent characteristics. The PPO transit peptide could drive thylakoid translocation of a Tat protein in the dark. Azide inhibited the secretion of a PPO intermediate that lacks a twin-Arg to the periplasm of Escherichia coli, but had no effect on the export of the intermediate containing the twin-Arg. PPO is synthesized in plants in response to wound and pathogen-related signals and it is possible that when the Tat pathway is unable to translocate adequate amounts of newly synthesized PPO, translocation is diverted to the Sec-dependent pathway by processing the intermediate at the second site and removing the twin-Arg.
Collapse
Affiliation(s)
- Shai Koussevitzky
- Department of Plant Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | | | | | | |
Collapse
|
23
|
Inserting proteins into the bacterial cytoplasmic membrane using the Sec and YidC translocases. Nat Rev Microbiol 2008; 6:234-44. [PMID: 18246081 DOI: 10.1038/nrmicro3595] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This Review describes the pathways that are used to insert newly synthesized proteins into the cytoplasmic membranes of bacteria, and provides insight into the function of two of the evolutionarily conserved translocases that catalyse this process. These highly sophisticated translocases are responsible for decoding the topogenic sequences within membrane proteins that direct membrane protein insertion and orientation. The role of the Sec and YidC translocases in the folding of bacterial membrane proteins is also highlighted.
Collapse
|
24
|
Jensen PE, Bassi R, Boekema EJ, Dekker JP, Jansson S, Leister D, Robinson C, Scheller HV. Structure, function and regulation of plant photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:335-52. [PMID: 17442259 DOI: 10.1016/j.bbabio.2007.03.004] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Revised: 03/03/2007] [Accepted: 03/06/2007] [Indexed: 12/20/2022]
Abstract
Photosystem I (PSI) is a multisubunit protein complex located in the thylakoid membranes of green plants and algae, where it initiates one of the first steps of solar energy conversion by light-driven electron transport. In this review, we discuss recent progress on several topics related to the functioning of the PSI complex, like the protein composition of the complex in the plant Arabidopsis thaliana, the function of these subunits and the mechanism by which nuclear-encoded subunits can be inserted into or transported through the thylakoid membrane. Furthermore, the structure of the native PSI complex in several oxygenic photosynthetic organisms and the role of the chlorophylls and carotenoids in the antenna complexes in light harvesting and photoprotection are reviewed. The special role of the 'red' chlorophylls (chlorophyll molecules that absorb at longer wavelength than the primary electron donor P700) is assessed. The physiology and mechanism of the association of the major light-harvesting complex of photosystem II (LHCII) with PSI during short term adaptation to changes in light quality and quantity is discussed in functional and structural terms. The mechanism of excitation energy transfer between the chlorophylls and the mechanism of primary charge separation is outlined and discussed. Finally, a number of regulatory processes like acclimatory responses and retrograde signalling is reviewed with respect to function of the thylakoid membrane. We finish this review by shortly discussing the perspectives for future research on PSI.
Collapse
Affiliation(s)
- Poul Erik Jensen
- Plant Biochemistry Laboratory, Department of Plant Biology, Faculty of Life Science, University of Copenhagen, DK-1871 Frederiksberg C, Denmark.
| | | | | | | | | | | | | | | |
Collapse
|
25
|
Abstract
The thylakoid membrane of chloroplasts contains the major photosynthetic complexes, which consist of several either nuclear or chloroplast encoded subunits. The biogenesis of these thylakoid membrane complexes requires coordinated transport and subsequent assembly of the subunits into functional complexes. Nuclear-encoded thylakoid proteins are first imported into the chloroplast and then directed to the thylakoid using different sorting mechanisms. The cpSec pathway and the cpTat pathway are mainly involved in the transport of lumenal proteins, whereas the spontaneous pathway and the cpSRP pathway are used for the insertion of integral membrane proteins into the thylakoid membrane. While cpSec-, cpTat- and cpSRP-mediated targeting can be classified as 'assisted' mechanisms involving numerous components, 'unassisted' spontaneous insertion does not require additional targeting factors. However, even the assisted pathways differ fundamentally with respect to stromal targeting factors, the composition of the translocase and energy requirements.
Collapse
Affiliation(s)
- Danja Schünemann
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
| |
Collapse
|
26
|
Cline K, Theg SM. The Sec and Tat Protein Translocation Pathways in Chloroplasts. MOLECULAR MACHINES INVOLVED IN PROTEIN TRANSPORT ACROSS CELLULAR MEMBRANES 2007. [DOI: 10.1016/s1874-6047(07)25018-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
27
|
Sun C, Rusch SL, Kim J, Kendall DA. Chloroplast SecA and Escherichia coli SecA have distinct lipid and signal peptide preferences. J Bacteriol 2006; 189:1171-5. [PMID: 17142391 PMCID: PMC1797313 DOI: 10.1128/jb.01589-06] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Like prokaryotic Sec-dependent protein transport, chloroplasts utilize SecA. However, we observe distinctive requirements for the stimulation of chloroplast SecA ATPase activity; it is optimally stimulated in the presence of galactolipid and only a small fraction of anionic lipid and by Sec-dependent thylakoid signal peptides but not Escherichia coli signal peptides.
Collapse
Affiliation(s)
- Changqi Sun
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269-3125, USA
| | | | | | | |
Collapse
|
28
|
Dabney-Smith C, Mori H, Cline K. Oligomers of Tha4 organize at the thylakoid Tat translocase during protein transport. J Biol Chem 2006; 281:5476-83. [PMID: 16407186 DOI: 10.1074/jbc.m512453200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Tat (twin arginine translocation) systems of thylakoids and bacteria transport fully folded protein substrates without breaching the permeability barrier of the membrane. Two components of the thylakoid system, cpTatC and Hcf106, compose a precursor-bound receptor complex. The third component, Tha4, assembles with the precursor-bound receptor complex for the translocation step and is thought to compose at least part of the protein-conducting channel. Here, we used two different cross-linking approaches to explore the organization of Tha4 in the translocase. These cross-linking techniques showed that transition to an active protein transport state resulted in an alignment of the Tha4 amphipathic helix and C-terminal tail domains to form Tha4 oligomers. Oligomerization required functional Tha4, a twin arginine signal peptide, and an active cpTatC-Hcf106 receptor complex. The spectrum of oligomers obtained was independent of the mature folded domain of the precursor. We propose a trapdoor mechanism for translocation whereby aligned oligomers of Tha4 amphipathic helices fold into the membrane to allow formfitting passage of precursor proteins.
Collapse
Affiliation(s)
- Carole Dabney-Smith
- Horticultural Sciences Department and the Plant Molecular and Cellular Biology Program, University of Florida, 1109 Fifield Hall, Gainesville, FL 32611, USA
| | | | | |
Collapse
|
29
|
Gutensohn M, Fan E, Frielingsdorf S, Hanner P, Hou B, Hust B, Klösgen RB. Toc, Tic, Tat et al.: structure and function of protein transport machineries in chloroplasts. JOURNAL OF PLANT PHYSIOLOGY 2006; 163:333-47. [PMID: 16386331 DOI: 10.1016/j.jplph.2005.11.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Accepted: 11/13/2005] [Indexed: 05/05/2023]
Abstract
The chloroplast is an organelle of prokaryotic origin that is situated in an eukaryotic cellular environment. As a result of this formerly endosymbiotic situation, the chloroplast houses a unique set of protein transport machineries. Among those are evolutionarily young transport pathways which are responsible for the import of the nuclear-encoded proteins into the organelle as well as ancient pathways operating in the 'export' of proteins from the stroma (the former cyanobacterial cytosol) across the thylakoid membrane into the thylakoid lumen. In this review, we have tried to address the main features of these various transport pathways.
Collapse
Affiliation(s)
- Michael Gutensohn
- Institut für Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, D-06120 Halle (Saale), Germany
| | | | | | | | | | | | | |
Collapse
|
30
|
Inoue K, Baldwin AJ, Shipman RL, Matsui K, Theg SM, Ohme-Takagi M. Complete maturation of the plastid protein translocation channel requires a type I signal peptidase. J Cell Biol 2005; 171:425-30. [PMID: 16275749 PMCID: PMC2171254 DOI: 10.1083/jcb.200506171] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Accepted: 09/28/2005] [Indexed: 11/22/2022] Open
Abstract
The protein translocation channel at the plastid outer envelope membrane, Toc75, is essential for the viability of plants from the embryonic stage. It is encoded in the nucleus and is synthesized with a bipartite transit peptide that is cleaved during maturation. Despite its important function, the molecular mechanism and the biological significance of the full maturation of Toc75 remain unclear. In this study, we show that a type I signal peptidase (SPase I) is responsible for this process. First, we demonstrate that a bacterial SPase I converted Toc75 precursor to its mature form in vitro. Next, we show that disruption of a gene encoding plastidic SPase I (Plsp1) resulted in the accumulation of immature forms of Toc75, severe reduction of plastid internal membrane development, and a seedling lethal phenotype. These phenotypes were rescued by the overexpression of Plsp1 complementary DNA. Plsp1 appeared to be targeted both to the envelope and to the thylakoidal membranes; thus, it may have multiple functions.
Collapse
Affiliation(s)
- Kentaro Inoue
- Department of Plant Sciences, College of Agricultural and Environmental Sciences, University of California, Davis, CA 95616, USA.
| | | | | | | | | | | |
Collapse
|
31
|
The complexity of pathways for protein import into thylakoids: it's not easy being green. Biochem Soc Trans 2005. [DOI: 10.1042/bst0331024] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Numerous proteins are transported into or across the chloroplast thylakoid membrane. To date, two major pathways have been identified for the transport of luminal proteins (the Sec- and Tat-dependent pathways) and it is now clear that these protein translocases use fundamentally different transport mechanisms. Integral membrane proteins are inserted by means of at least two further pathways. One involves the input of numerous targeting factors, including SRP (signal recognition particle), FtsY and Albino3. Surprisingly, the other pathway does not involve any of the known chloroplastic targeting factors, and insertion is energy-independent, raising the possibility of an unusual ‘spontaneous’ insertion mechanism.
Collapse
|
32
|
Abstract
The vast majority of the approximately 3000 different proteins required to build a fully functional chloroplast are encoded by the nuclear genome and translated on cytosolic ribosomes. As chloroplasts are each surrounded by a double-membrane system, or envelope, sophisticated mechanisms are necessary to mediate the import of these nucleus-encoded proteins into chloroplasts. Once inside the organelle, many chloroplast proteins engage one of four additional protein sorting mechanisms that direct targeting to the internal thylakoid membrane system.
Collapse
Affiliation(s)
- Paul Jarvis
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK.
| | | |
Collapse
|
33
|
Peltier JB, Ytterberg AJ, Sun Q, van Wijk KJ. New Functions of the Thylakoid Membrane Proteome of Arabidopsis thaliana Revealed by a Simple, Fast, and Versatile Fractionation Strategy. J Biol Chem 2004; 279:49367-83. [PMID: 15322131 DOI: 10.1074/jbc.m406763200] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Identification of membrane proteomes remains challenging. Here, we present a simple, fast, and scalable off-line procedure based on three-phase partitioning with butanol to fractionate membrane proteomes in combination with both in-gel and in-solution digestions and mass spectrometry. This should help to further accelerate the field of membrane proteomics. Using this new strategy, we analyzed the salt-stripped thylakoid membrane of chloroplasts of Arabidopsis thaliana. 242 proteins were identified, at least 40% of which are integral membrane proteins. The functions of 86 proteins are unknown; these include proteins with TPR, PPR, rhodanese, and DnaJ domains. These proteins were combined with all known thylakoid proteins and chloroplast (associated) envelope proteins, collected from primary literature, resulting in 714 non-redundant proteins. They were assigned to functional categories using a classification developed for MapMan (Thimm, O., Blasing, O., Gibon, Y., Nagel, A., Meyer, S., Kruger, P., Selbig, J., Muller, L. A., Rhee, S. Y., and Stitt, M. (2004) Plant J. 37, 914-939), updated with information from primary literature. The analysis elucidated the likely location of many membrane proteins, including 190 proteins of unknown function, holding the key to better understanding the two membrane systems. The three-phase partitioning procedure added a new level of dynamic resolution to the known thylakoid proteome. An automated strategy was developed to track possible ambiguous identifications to more than one gene model or family member. Mass spectrometry search results, ambiguities, and functional classifications can be searched via the Plastid Proteome Database.
Collapse
|
34
|
Spence E, Bailey S, Nenninger A, Møller SG, Robinson C. A homolog of Albino3/OxaI is essential for thylakoid biogenesis in the cyanobacterium Synechocystis sp. PCC6803. J Biol Chem 2004; 279:55792-800. [PMID: 15498761 DOI: 10.1074/jbc.m411041200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
YidC/OxaI play essential roles in the insertion of a wide range of membrane proteins in Eschericha coli and mitochondria, respectively. In contrast, the chloroplast thylakoid homolog Albino3 (Alb3) facilitates the insertion of only a specialized subset of proteins, and the vast majority insert into thylakoids by a pathway that is so far unique to chloroplasts. In this study, we have analyzed the role of Alb3 in the cyanobacterium Synechocystis sp. PCC6803, which contains internal thylakoids that are similar in some respects to those of chloroplasts. The single alb3 gene (slr1471) was disrupted by the introduction of an antibiotic cassette, and photoautotrophic growth resulted in the generation of a merodiploid species (but not full segregation), indicating an essential role for Alb3 in maintaining the photosynthetic apparatus. Thylakoid organization is lost under these conditions, and the levels of photosynthetic pigments fall to approximately 40% of wild-type levels. Photosynthetic electron transport and oxygen evolution are reduced by a similar extent. Growth on glucose relieves the selective pressure to maintain photosynthetic competence, and under these conditions, the cells become completely bleached, again indicating that Alb3 is essential for thylakoid biogenesis. Full segregation could not be achieved under any growth regime, strongly suggesting that the slr1471 open reading frame is essential for cell viability.
Collapse
Affiliation(s)
- Edward Spence
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
| | | | | | | | | |
Collapse
|
35
|
Chou ML, Fitzpatrick LM, Tu SL, Budziszewski G, Potter-Lewis S, Akita M, Levin JZ, Keegstra K, Li HM. Tic40, a membrane-anchored co-chaperone homolog in the chloroplast protein translocon. EMBO J 2003; 22:2970-80. [PMID: 12805212 PMCID: PMC162133 DOI: 10.1093/emboj/cdg281] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The function of Tic40 during chloroplast protein import was investigated. Tic40 is an inner envelope membrane protein with a large hydrophilic domain located in the stroma. Arabidopsis null mutants of the atTic40 gene were very pale green and grew slowly but were not seedling lethal. Isolated mutant chloroplasts imported precursor proteins at a lower rate than wild-type chloroplasts. Mutant chloroplasts were normal in allowing binding of precursor proteins. However, during subsequent translocation across the inner membrane, fewer precursors were translocated and more precursors were released from the mutant chloroplasts. Cross-linking experiments demonstrated that Tic40 was part of the translocon complex and functioned at the same stage of import as Tic110 and Hsp93, a member of the Hsp100 family of molecular chaperones. Tertiary structure prediction and immunological studies indicated that the C-terminal portion of Tic40 contains a TPR domain followed by a domain with sequence similarity to co-chaperones Sti1p/Hop and Hip. We propose that Tic40 functions as a co-chaperone in the stromal chaperone complex that facilitates protein translocation across the inner membrane.
Collapse
Affiliation(s)
- Ming-Lun Chou
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Kroth PG. Protein transport into secondary plastids and the evolution of primary and secondary plastids. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 221:191-255. [PMID: 12455749 DOI: 10.1016/s0074-7696(02)21013-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Chloroplasts are key organelles in algae and plants due to their photosynthetic abilities. They are thought to have evolved from prokaryotic cyanobacteria taken up by a eukaryotic host cell in a process termed primary endocytobiosis. In addition, a variety of organisms have evolved by subsequent secondary endocytobioses, in which a heterotrophic host cell engulfed a eukaryotic alga. Both processes dramatically enhanced the complexity of the resulting cells. Since the first version of the endosymbiotic theory was proposed more than 100 years ago, morphological, physiological, biochemical, and molecular data have been collected substantiating the emerging picture about the origin and the relationship of individual organisms with different primary or secondary chloroplast types. Depending on their origin, plastids in different lineages may have two, three, or four envelope membranes. The evolutionary success of endocytobioses depends, among other factors, on the specific exchange of molecules between the host and endosymbiont. This raises questions concerning how targeting of nucleus-encoded proteins into the different plastid types occurs and how these processes may have developed. Most studies of protein translocation into plastids have been performed on primary plastids, but in recent years more complex protein-translocation systems of secondary plastids have been investigated. Analyses of transport systems in different algal lineages with secondary plastids reveal that during evolution existing translocation machineries were recycled or recombined rather than being developed de novo. This review deals with current knowledge about the evolution and function of primary and secondary plastids and the respective protein-targeting systems.
Collapse
Affiliation(s)
- Peter G Kroth
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
37
|
Fitter DW, Martin DJ, Copley MJ, Scotland RW, Langdale JA. GLK gene pairs regulate chloroplast development in diverse plant species. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 31:713-27. [PMID: 12220263 DOI: 10.1046/j.1365-313x.2002.01390.x] [Citation(s) in RCA: 224] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chloroplast biogenesis is a complex process that requires close co-ordination between two genomes. Many of the proteins that accumulate in the chloroplast are encoded by the nuclear genome, and the developmental transition from proplastid to chloroplast is regulated by nuclear genes. Here we show that a pair of Golden 2-like (GLK) genes regulates chloroplast development in Arabidopsis. The GLK proteins are members of the GARP superfamily of transcription factors, and phylogenetic analysis demonstrates that the maize, rice and Arabidopsis GLK gene pairs comprise a distinct group within the GARP superfamily. Further phylogenetic analysis suggests that the gene pairs arose through separate duplication events in the monocot and dicot lineages. As in rice, AtGLK1 and AtGLK2 are expressed in partially overlapping domains in photosynthetic tissue. Insertion mutants demonstrate that this expression pattern reflects a degree of functional redundancy as single mutants display normal phenotypes in most photosynthetic tissues. However, double mutants are pale green in all photosynthetic tissues and chloroplasts exhibit a reduction in granal thylakoids. Products of several genes involved in light harvesting also accumulate at reduced levels in double mutant chloroplasts. GLK genes therefore regulate chloroplast development in diverse plant species.
Collapse
Affiliation(s)
- David W Fitter
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | | | | | | | | |
Collapse
|
38
|
Yuan J, Kight A, Goforth RL, Moore M, Peterson EC, Sakon J, Henry R. ATP stimulates signal recognition particle (SRP)/FtsY-supported protein integration in chloroplasts. J Biol Chem 2002; 277:32400-4. [PMID: 12105232 DOI: 10.1074/jbc.m206192200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signal recognition particle (SRP) and its receptor (FtsY in prokaryotes) are essential for cotranslational protein targeting to the endoplasmic reticulum in eukaryotes and the cytoplasmic membrane in prokaryotes. An SRP/FtsY-like protein targeting/integration pathway in chloroplasts mediates the posttranslational integration of the light-harvesting chlorophyll a/b-binding protein (LHCP) into thylakoid membranes. GTP, chloroplast SRP (cpSRP), and chloroplast FtsY (cpFtsY) are required for LHCP integration into thylakoid membranes. Here, we report the reconstitution of the LHCP integration reaction with purified recombinant proteins and salt-washed thylakoids. Our data demonstrate that cpSRP and cpFtsY are the only soluble protein components required for LHCP integration. In addition, our studies reveal that ATP, though not absolutely required, remarkably stimulates LHCP integration into salt-washed thylakoids. ATP stimulates LHCP integration by a mechanism independent of the thylakoidal pH gradient (DeltapH) and exerts no detectable effect on the formation of the soluble LHCP-cpSRP-targeting complex. Taken together, our results indicate the participation of a thylakoid ATP-binding protein in LHCP integration.
Collapse
Affiliation(s)
- Jianguo Yuan
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | | | | | | | | | | | | |
Collapse
|
39
|
Steiner JM, Köcher T, Nagy C, Löffelhardt W. Chloroplast SecE: evidence for spontaneous insertion into the thylakoid membrane. Biochem Biophys Res Commun 2002; 293:747-52. [PMID: 12054533 DOI: 10.1016/s0006-291x(02)00285-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
SecE, an essential component of the bacterial SecAYEG translocase, mediates protein translocation across the cytoplasmic membrane. In the thylakoid membranes of chloroplasts an SecE homologue, cpSecE, has recently been identified. In this report we show that insertion of cpSecE does not require stromal extract, indicating that signal recognition particle is not involved. Removal of nucleoside triphosphates has apparently no effect on the integration, again ruling out an involvement of SRP or its partner protein, FtsY. The use of well-known inhibitors of the Sec- and Tat pathways, sodium azide and nigericin, respectively, also had no influence on membrane insertion. The data presented here point towards cpSecE as another passenger of a wholly spontaneous import/insertion pathway in the thylakoids of chloroplasts.
Collapse
Affiliation(s)
- Jürgen M Steiner
- Institut für Biochemie und Molekulare Zellbiologie der Universität Wien, Ludwig-Boltzmann-Forschungsstelle für Biochemie, Dr. Bohrgasse 9, A-1030 Vienna, Austria
| | | | | | | |
Collapse
|
40
|
Mori H, Cline K. Post-translational protein translocation into thylakoids by the Sec and DeltapH-dependent pathways. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1541:80-90. [PMID: 11750664 DOI: 10.1016/s0167-4889(01)00150-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Two distinct protein translocation pathways that employ hydrophobic signal peptides function in the plant thylakoid membrane. These two systems are precursor specific and distinguished by their energy and component requirements. Recent studies have shown that one pathway is homologous to the bacterial general export system called Sec. The other one, called the DeltapH-dependent pathway, was originally considered to be unique to plant thylakoids. However, it is now known that homologous transport systems are widely present in prokaryotes and even present in archaea. Here we review these protein transport pathways and discuss their capabilities and mechanisms of operation.
Collapse
Affiliation(s)
- H Mori
- Horticultural Sciences and Plant Molecular and Cellular Biology, University of Florida, 1137 Fifield Hall, Gainesville, FL 32611, USA
| | | |
Collapse
|
41
|
Molik S, Karnauchov I, Weidlich C, Herrmann RG, Klösgen RB. The Rieske Fe/S protein of the cytochrome b6/f complex in chloroplasts: missing link in the evolution of protein transport pathways in chloroplasts? J Biol Chem 2001; 276:42761-6. [PMID: 11526115 DOI: 10.1074/jbc.m106690200] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rieske Fe/S protein, a nuclear-encoded subunit of the cytochrome b(6)/f complex in chloroplasts, is retarded in the stromal space after import into the chloroplast and only slowly translocated further into the thylakoid membrane system. As shown by the sensitivity to nigericin and to specific competitor proteins, thylakoid transport takes place by the DeltapH-dependent TAT pathway. The Rieske protein is an untypical TAT substrate, however. It is only the second integral membrane protein shown to utilize this pathway, and it is the first authentic substrate without a cleavable signal peptide. Transport is instead mediated by the NH(2)-terminal membrane anchor, which lacks, however, the twin-arginine motif indicative of DeltapH/TAT-dependent transport signals. Furthermore, transport is affected by sodium azide as well as by competitor proteins for the Sec pathway in chloroplasts, demonstrating for the first time some cross-talk of the two pathways. This might take place in the stroma where the Rieske protein accumulates after import in several complexes of high molecular mass, among which the cpn60 complex is the most prominent. These untypical features suggest that the Rieske protein represents an intermediate or early state in the evolution of the thylakoidal protein transport pathways.
Collapse
Affiliation(s)
- S Molik
- Institut für Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, D-06120 Halle (Saale), Germany
| | | | | | | | | |
Collapse
|
42
|
Röhl T, van Wijk KJ. In vitro reconstitution of insertion and processing of cytochrome f in a homologous chloroplast translation system. J Biol Chem 2001; 276:35465-72. [PMID: 11459839 DOI: 10.1074/jbc.m103005200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Using a homologous chloroplast translation system, we have reconstituted insertion and processing of the chloroplast-encoded thylakoid protein cytochrome f (pCytf). Cross-linking demonstrated that pCytf nascent chains when attached to the 70 S ribosome tightly interact with cpSecA, but this is strictly dependent on thylakoid membranes and a functional signal peptide. This indicates that cpSecA is only operative in pCytf biogenesis when it is bound to the membrane, most likely as part of the Sec translocon. No evidence for interaction between the 54-kDa subunit of the chloroplast signal recognition particle (cpSRP) and the pCytf nascent chain could be detected, suggesting that pCytf, in contrast to the polytopic D1 protein, does not require cpSRP for targeting. Insertion of pCytf occurred only co-translationally, resulting in processing and accumulation of both the processed signal peptide and the mature protein in the thylakoid. This co-translational membrane insertion and processing required a functional signal peptide and was inhibited by azide, demonstrating that cpSecA is essential for translocation of the soluble luminal domain. pCytf also associated post-translationally with thylakoids, but the soluble N-terminal domain could not be translocated into the lumen. This is the first study in which synthesis, targeting, and insertion of a chloroplast-encoded thylakoid membrane protein is reconstituted from exogenous transcripts and using the chloroplast translational machinery.
Collapse
Affiliation(s)
- T Röhl
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
| | | |
Collapse
|
43
|
Motohashi R, Nagata N, Ito T, Takahashi S, Hobo T, Yoshida S, Shinozaki K. An essential role of a TatC homologue of a Delta pH- dependent protein transporter in thylakoid membrane formation during chloroplast development in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2001; 98:10499-504. [PMID: 11526245 PMCID: PMC56989 DOI: 10.1073/pnas.181304598] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2001] [Accepted: 06/15/2001] [Indexed: 11/18/2022] Open
Abstract
At least three transport systems function in targeting nuclear-encoded chloroplast proteins to the chloroplast thylakoid membrane. One of these systems requires a thylakoid pH gradient and is named the DeltapH-dependent protein transport system. A similar DeltapH export system of Escherichia coli contains four components, twin arginine translocation A (TatA), TatB, TatC, and TatE. TatC is a major component of the DeltapH-dependent protein transporter in E. coli and functions in the translocation of tightly folded proteins across membranes. We have isolated four transposon-inserted albino mutants named albino and pale green 2 (apg2) from Arabidopsis thaliana and showed that the transposons were inserted into different sites of a single gene. The APG2 gene product (named cpTatC) has sequence similarity with bacterial TatC and contains six putative transmembrane domains, including bacterial TatC proteins and a transit peptide in its N terminus. apg2 mutants showed albino phenotypes and could not grow in soil. The apg2 plastids were highly vacuolated, lacked internal membrane structures and lamellae of the thylakoid membrane, and contained many densely stained globule structures, like undifferentiated proplastids. Immunoblot analysis detected no thylakoid membrane proteins such as D1, light-harvesting complex, and OE23 in apg2 plastids, whereas soluble proteins such as rubisco large and small subunits were not decreased. These results indicate an essential role of cpTatC in chloroplast development, especially in thylakoid membrane formation.
Collapse
Affiliation(s)
- R Motohashi
- Plant Functional Genomics Group, The Institute of Physical and Chemical Research (Japan) (RIKEN) Genomic Sciences Center, 3-1-1 Koyadai, Tsukuba 305-0074, Japan
| | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
Cellular membranes act as semipermeable barriers to ions and macromolecules. Specialized mechanisms of transport of proteins across membranes have been developed during evolution. There are common mechanistic themes among protein translocation systems in bacteria and in eukaryotic cells. Here we review current understanding of mechanisms of protein transport across the bacterial plasma membrane as well as across several organelle membranes of yeast and mammalian cells. We consider a variety of organelles including the endoplasmic reticulum, outer and inner membranes of mitochondria, outer, inner, and thylakoid membranes of chloroplasts, peroxisomes, and lysosomes. Several common principles are evident: (a) multiple pathways of protein translocation across membranes exist, (b) molecular chaperones are required in the cytosol, inside the organelle, and often within the organelle membrane, (c) ATP and/or GTP hydrolysis is required, (d) a proton-motive force across the membrane is often required, and (e) protein translocation occurs through gated, aqueous channels. There are exceptions to each of these common principles indicating that our knowledge of how proteins translocate across membranes is not yet complete.
Collapse
Affiliation(s)
- F A Agarraberes
- Department of Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | | |
Collapse
|
45
|
Fröderberg L, Röhl T, van Wijk KJ, de Gier JW. Complementation of bacterial SecE by a chloroplastic homologue. FEBS Lett 2001; 498:52-6. [PMID: 11389897 DOI: 10.1016/s0014-5793(01)02494-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The SecE protein is an essential component of the SecAYE-translocase, which mediates protein translocation across the cytoplasmic membrane in bacteria. In the thylakoid membranes of chloroplasts, a protein homologous to SecE, chloroplastic (cp) SecE, has been identified. However, the functional role of cpSecE has not been established experimentally. In this report we show that cpSecE in cells depleted for bacterial SecE (i) supports growth, (ii) stabilizes, just like bacterial SecE, the Sec-translocase core component SecY, and (iii) supports Sec-dependent protein translocation. This indicates that cpSecE can functionally replace bacterial SecE in vivo, and strongly suggests that the thylakoid membrane contains a SecAYE-like translocase with functional and structural similarities to the bacterial complex. This study further underscores the evolutionary link between chloroplasts and bacteria.
Collapse
Affiliation(s)
- L Fröderberg
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | | | | | | |
Collapse
|
46
|
Robinson C, Bolhuis A. Protein targeting by the twin-arginine translocation pathway. Nat Rev Mol Cell Biol 2001; 2:350-6. [PMID: 11331909 DOI: 10.1038/35073038] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The twin-arginine translocation pathway operates in the thylakoid membrane of chloroplasts and in the plasma membrane of most free-living bacteria. Its main function is to transport fully folded proteins across the membrane. Three important tat genes have been identified and the sequences of the encoded proteins, together with the unusual properties of the pathway, indicate that the Tat system is completely different from other protein translocases.
Collapse
Affiliation(s)
- C Robinson
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom.
| | | |
Collapse
|
47
|
Robinson C, Thompson SJ, Woolhead C. Multiple pathways used for the targeting of thylakoid proteins in chloroplasts. Traffic 2001; 2:245-51. [PMID: 11285134 DOI: 10.1034/j.1600-0854.2001.1r010.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The assembly of the chloroplast thylakoid membrane requires the import of numerous proteins from the cytosol and their targeting into or across the thylakoid membrane. It is now clear that multiple pathways are involved in the thylakoid-targeting stages, depending on the type of protein substrate. Two very different pathways are used by thylakoid lumen proteins; one is the Sec pathway which has been well-characterised in bacteria, and which involves the threading of the substrate through a narrow channel. In contrast, the more recently characterised twin-arginine translocation (Tat) system is able to translocate fully folded proteins across this membrane. Recent advances on bacterial Tat systems shed further light on the structure and function of this system. Membrane proteins, on the other hand, use two further pathways. One is the signal recognition particle-dependent pathway, involving a complex interplay between many different factors, whereas other proteins insert without the assistance of any known apparatus. This article reviews advances in the study of these pathways and considers the rationale behind the surprising complexity.
Collapse
Affiliation(s)
- C Robinson
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom.
| | | | | |
Collapse
|
48
|
Proteins Involved in Biogenesis of the Thylakoid Membrane. REGULATION OF PHOTOSYNTHESIS 2001. [DOI: 10.1007/0-306-48148-0_9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
|
49
|
Settles AM, Baron A, Barkan A, Martienssen RA. Duplication and suppression of chloroplast protein translocation genes in maize. Genetics 2001; 157:349-60. [PMID: 11139515 PMCID: PMC1461481 DOI: 10.1093/genetics/157.1.349] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The HCF106 (high chlorophyll fluorescence) gene of maize encodes a chloroplast membrane protein required for translocation of a subset of proteins across the thylakoid membrane. Mutations in HCF106 caused by the insertion of Robertson's Mutator transposable elements have been mapped to chromosome 2S. Here we show that there is a closely related homolog of HCF106 encoded elsewhere in the maize genome (HCF106c) that can partially compensate for these mutations. This homolog maps on chromosome 10L and is part of the most recent set of segmental duplications in the maize genome. Triple mutants that are disrupted in both the HCF106 and Sec-dependent protein translocation pathways provide evidence that they act independently. The HCF106c gene accounts for a previously reported exception to the correlation between epigenetic suppression of hcf106 and methylation of Mutator transposons. We also demonstrate that insertions of Robertson's Mutator elements into either introns or promoters can lead to mutations whose phenotypes are suppressed in the absence of Mu activity, while alleles with insertions in both positions are not suppressed. The implications of these observations are discussed.
Collapse
Affiliation(s)
- A M Settles
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | | | | | | |
Collapse
|
50
|
Inagaki J, Fujita Y, Hase T, Yamamoto Y. Protein translocation within chloroplast is similar in Euglena and higher plants. Biochem Biophys Res Commun 2000; 277:436-42. [PMID: 11032741 DOI: 10.1006/bbrc.2000.3702] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is currently thought that chloroplasts of higher plants were derived from endosymbiont oxygenic photosynthetic bacteria (primary endosymbiosis), while Euglena, a photosynthetic protista, gained chloroplasts by secondary endosymbiosis (i.e., incorporation of a photosynthetic eukaryote into heterotrophic eukaryotic host). To examine if the protein transport inside chloroplasts is similar between these organisms, we carried out heterologous protein import experiments with Euglena precursor proteins and spinach chloroplasts. The precursor of a 30-kDa subunit of the oxygen-evolving complex (OEC30) from the thylakoid lumen of Euglena chloroplasts contained the N-terminal signal, stroma targeting, and thylakoid transfer domains. Truncated preOEC30s lacking the N-terminal domain were post-translationally imported into spinach chloroplasts, transported into the thylakoid lumen, and processed to a mature protein. These results showed that protein translocations within chloroplasts in Euglena and higher plants are similar and supported the hypothesis that Euglena chloroplasts are derived from the ancestral Chlorophyta.
Collapse
Affiliation(s)
- J Inagaki
- Department of Cell Chemistry, Institute of Cellular and Molecular Biology, Okayama, 700-8558, Japan.
| | | | | | | |
Collapse
|