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Abstract
The folding of proteins into their native structure is crucial for the functioning of all biological processes. Molecular chaperones are guardians of the proteome that assist in protein folding and prevent the accumulation of aberrant protein conformations that can lead to proteotoxicity. ATP-independent chaperones do not require ATP to regulate their functional cycle. Although these chaperones have been traditionally regarded as passive holdases that merely prevent aggregation, recent work has shown that they can directly affect the folding energy landscape by tuning their affinity to various folding states of the client. This review focuses on emerging paradigms in the mechanism of action of ATP-independent chaperones and on the various modes of regulating client binding and release.
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Affiliation(s)
- Rishav Mitra
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, Michigan, USA; .,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Kevin Wu
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, Michigan, USA; .,Department of Biophysics, University of Michigan, Ann Arbor, Michigan, USA
| | - Changhan Lee
- Department of Biological Sciences, Ajou University, Suwon, South Korea
| | - James C A Bardwell
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, Michigan, USA; .,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
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2
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Ji M, Zhao J, Han K, Cui W, Wu X, Chen B, Lu Y, Peng J, Zheng H, Rao S, Wu G, Chen J, Yan F. Turnip mosaic virus P1 suppresses JA biosynthesis by degrading cpSRP54 that delivers AOCs onto the thylakoid membrane to facilitate viral infection. PLoS Pathog 2021; 17:e1010108. [PMID: 34852025 PMCID: PMC8668097 DOI: 10.1371/journal.ppat.1010108] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 12/13/2021] [Accepted: 11/11/2021] [Indexed: 11/18/2022] Open
Abstract
Jasmonic acid (JA) is a crucial hormone in plant antiviral immunity. Increasing evidence shows that viruses counter this host immune response by interfering with JA biosynthesis and signaling. However, the mechanism by which viruses affect JA biosynthesis is still largely unexplored. Here, we show that a highly conserved chloroplast protein cpSRP54 was downregulated in Nicotiana benthamiana infected by turnip mosaic virus (TuMV). Its silencing facilitated TuMV infection. Furthermore, cpSRP54 interacted with allene oxide cyclases (AOCs), key JA biosynthesis enzymes, and was responsible for delivering AOCs onto the thylakoid membrane (TM). Interestingly, TuMV P1 protein interacted with cpSRP54 and mediated its degradation via the 26S proteosome and autophagy pathways. The results suggest that TuMV has evolved a strategy, through the inhibition of cpSRP54 and its delivery of AOCs to the TM, to suppress JA biosynthesis and enhance viral infection. Interaction between cpSRP54 and AOCs was shown to be conserved in Arabidopsis and rice, while cpSRP54 also interacted with, and was degraded by, pepper mild mottle virus (PMMoV) 126 kDa protein and potato virus X (PVX) p25 protein, indicating that suppression of cpSRP54 may be a common mechanism used by viruses to counter the antiviral JA pathway. Jasmonic acid pathway has emerged as one of the predominant battlefields between plants and viruses. Several studies have indicated that, in addition to interfering with JA signaling, plant viruses can also affect JA biosynthesis, but the direct molecular links between them remain elusive. Here, we identify a highly conserved chloroplast protein cpSRP54 as a key positive regulator in JA biosynthesis and a common target for viruses belong to different genera. Through associating with cpSRP54 and inducing its degradation using the protein they encoded, the viruses can inhibit the cpSRP54-facilitated delivery of AOCs to the thylakoid membrane and manipulation of JA-mediated defense. This capability of viruses might define a novel and effective strategy against the antiviral JA pathway.
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Affiliation(s)
- Mengfei Ji
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Jinping Zhao
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Kelei Han
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
| | - Weijun Cui
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
| | - Xinyang Wu
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
| | - Binghua Chen
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
| | - Yuwen Lu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Jiejun Peng
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Hongying Zheng
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Shaofei Rao
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Guanwei Wu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Jianping Chen
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- * E-mail: (JC); (FY)
| | - Fei Yan
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China
- Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- * E-mail: (JC); (FY)
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Shi Y, He Y, Lv X, Wei Y, Zhang X, Xu X, Li L, Wu JL. Chloroplast SRP54s are Essential for Chloroplast Development in Rice. RICE (NEW YORK, N.Y.) 2020; 13:54. [PMID: 32761436 PMCID: PMC7410889 DOI: 10.1186/s12284-020-00415-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/29/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND The chloroplast signal recognition particle 54 (cpSRP54) is known for targeting the light-harvesting complex proteins to thylakoids and plays a critical role for chloroplast development in Arabidopsis, but little is known in rice. Here, we reported two homologous cpSRP54s that affect chloroplast development and plant survival in rice. RESULTS Two rice cpSRP54 homologues, OscpSRP54a and OscpSRP54b, were identified in present study. The defective OscpSRP54a (LOC_Os11g05552) was responsible for the pale green leaf phenotype of the viable pale green leaf 14 (pgl14) mutant. A single nucleotide substitution from G to A at the position 278, the first intron splicing site, was detected in LOC_Os11g05552 in pgl14. The wild type allele could rescue the mutant phenotype. Knockout lines of OscpSRP54b (LOC_Os11g05556) exhibited similar pale green phenotype to pgl14 with reduced chlorophyll contents and impaired chloroplast development, but showed apparently arrested-growth and died within 3 weeks. Both OscpSRP54a and OscpSRP54b were constitutively expressed mainly in shoots and leaves at the vegetative growth stage. Subcellular location indicated that both OscpSRP54a and OscpSRP54b were chloroplast-localized. Both OscpSRP54a and OscpSRP54b were able to interact with OscpSRP43, respectively. The transcript level of OscpSRP43 was significantly reduced while the transcript level of OscpSRP54b was apparently increased in pgl14. In contrast, the transcript levels of OscpSRP54a, OscpSRP43 and OscpSRP54b were all significantly decreased in OscpSRP54b knockout lines. CONCLUSION Our study demonstrated that both OscpSRP54a and OscpSRP54b were essential for normal chloroplast development by interacting with OscpSRP43 in rice. OscpSRP54a and OscpSRP54b might play distinct roles in transporting different chloroplast proteins into thylakoids through cpSRP-mediated pathway.
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Affiliation(s)
- Yongfeng Shi
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Yan He
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xiangguang Lv
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100081 China
| | - Yanlin Wei
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xiaobo Zhang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xia Xu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Liangjian Li
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Jian-li Wu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
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Wild K, Juaire KD, Soni K, Shanmuganathan V, Hendricks A, Segnitz B, Beckmann R, Sinning I. Reconstitution of the human SRP system and quantitative and systematic analysis of its ribosome interactions. Nucleic Acids Res 2019; 47:3184-3196. [PMID: 30649417 PMCID: PMC6451106 DOI: 10.1093/nar/gky1324] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 12/20/2018] [Accepted: 01/02/2019] [Indexed: 12/22/2022] Open
Abstract
Co-translational protein targeting to membranes depends on the regulated interaction of two ribonucleoprotein particles (RNPs): the ribosome and the signal recognition particle (SRP). Human SRP is composed of an SRP RNA and six proteins with the SRP GTPase SRP54 forming the targeting complex with the heterodimeric SRP receptor (SRαβ) at the endoplasmic reticulum membrane. While detailed structural and functional data are available especially for the bacterial homologs, the analysis of human SRP was impeded by the unavailability of recombinant SRP. Here, we describe the large-scale production of all human SRP components and the reconstitution of homogeneous SRP and SR complexes. Binding to human ribosomes is determined by microscale thermophoresis for individual components, assembly intermediates and entire SRP, and binding affinities are correlated with structural information available for all ribosomal contacts. We show that SRP RNA does not bind to the ribosome, while SRP binds with nanomolar affinity involving a two-step mechanism of the key-player SRP54. Ultrasensitive binding of SRP68/72 indicates avidity by multiple binding sites that are dominated by the C-terminus of SRP72. Our data extend the experimental basis to understand the mechanistic principles of co-translational targeting in mammals and may guide analyses of complex RNP–RNP interactions in general.
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Affiliation(s)
- Klemens Wild
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Keven D Juaire
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Komal Soni
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Vivekanandan Shanmuganathan
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Feodor-Lynen-Str. 25, D-81377 Munich, Germany
| | - Astrid Hendricks
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Bernd Segnitz
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Roland Beckmann
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Feodor-Lynen-Str. 25, D-81377 Munich, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
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5
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Ziehe D, Dünschede B, Schünemann D. Molecular mechanism of SRP-dependent light-harvesting protein transport to the thylakoid membrane in plants. PHOTOSYNTHESIS RESEARCH 2018; 138:303-313. [PMID: 29956039 PMCID: PMC6244792 DOI: 10.1007/s11120-018-0544-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 06/20/2018] [Indexed: 05/26/2023]
Abstract
The light-harvesting chlorophyll a/b binding proteins (LHCP) belong to a large family of membrane proteins. They form the antenna complexes of photosystem I and II and function in light absorption and transfer of the excitation energy to the photosystems. As nuclear-encoded proteins, the LHCPs are imported into the chloroplast and further targeted to their final destination-the thylakoid membrane. Due to their hydrophobicity, the formation of the so-called 'transit complex' in the stroma is important to prevent their aggregation in this aqueous environment. The posttranslational LHCP targeting mechanism is well regulated through the interaction of various soluble and membrane-associated protein components and includes several steps: the binding of the LHCP to the heterodimeric cpSRP43/cpSRP54 complex to form the soluble transit complex; the docking of the transit complex to the SRP receptor cpFtsY and the Alb3 translocase at the membrane followed by the release and integration of the LHCP into the thylakoid membrane in a GTP-dependent manner. This review summarizes the molecular mechanisms and dynamics behind the posttranslational LHCP targeting to the thylakoid membrane of Arabidopsis thaliana.
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Affiliation(s)
- Dominik Ziehe
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, Universitätsstraße 150, 44780, Bochum, Germany
| | - Beatrix Dünschede
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, Universitätsstraße 150, 44780, Bochum, Germany
| | - Danja Schünemann
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, Universitätsstraße 150, 44780, Bochum, Germany.
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Ye J, Yang YL, Wei XH, Niu XJ, Wang S, Xu Q, Yuan XP, Yu HY, Wang YP, Feng Y, Wang S. PGL3 is required for chlorophyll synthesis and impacts leaf senescence in rice. J Zhejiang Univ Sci B 2018; 19:263-273. [PMID: 29616502 DOI: 10.1631/jzus.b1700337] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rice leaf color mutants play a great role in research about the formation and development of chloroplasts and the genetic mechanism of the chlorophyll (Chl) metabolism pathway. pgl3 is a rice leaf color mutant derived from Xiushui11 (Oryza sativa L. spp. japonica), treated with ethyl methane sulfonate (EMS). The mutant exhibited a pale-green leaf (pgl) phenotype throughout the whole development as well as reduced grain quality. Map-based cloning of PGL3 revealed that it encodes the chloroplast signal recognition particle 43 kDa protein (cpSRP43). PGL3 affected the Chl synthesis by regulating the expression levels of the Chl synthesis-associated genes. Considerable reactive oxygen species were accumulated in the leaves of pgl3, and the transcription levels of its scavenging genes were down-regulated, indicating that pgl3 can accelerate senescence. In addition, high temperatures could inhibit the plant's growth and facilitate the process of senescence in pgl3.
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Affiliation(s)
- Jing Ye
- College of Agronomy, Shenyang Agricultural University, Shenyang 110866, China.,State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Yao-Long Yang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Xing-Hua Wei
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Xiao-Jun Niu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Shan Wang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Qun Xu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Xiao-Ping Yuan
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Han-Yong Yu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Yi-Ping Wang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Yue Feng
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China
| | - Shu Wang
- College of Agronomy, Shenyang Agricultural University, Shenyang 110866, China
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Complementation of a mutation in CpSRP43 causing partial truncation of light-harvesting chlorophyll antenna in Chlorella vulgaris. Sci Rep 2017; 7:17929. [PMID: 29263352 PMCID: PMC5738337 DOI: 10.1038/s41598-017-18221-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 12/07/2017] [Indexed: 12/17/2022] Open
Abstract
Photosynthesis of microalgae enables conversion of light energy into chemical energy to produce biomass and biomaterials. However, the efficiency of this process must be enhanced, and truncation of light-harvesting complex (LHC) has been suggested to improve photosynthetic efficiency. We reported an EMS-induced mutant (E5) showing partially reduced LHC in Chlorella vulgaris. We determined the mutation by sequencing the whole genome of WT and E5. Augustus gene prediction was used for determining CDS, and non-synonymous changes in E5 were screened. Among these, we found a point mutation (T to A) in a gene homologous to chloroplast signal recognition particle 43 kDa (CpSRP43). The point mutation changed the 102nd valine to glutamic acid (V102E) located in the first chromodomain. Phylogenetic analyses of CpSRP43 revealed that this amino acid was valine or isoleucine in microalgae and plants, suggesting important functions. Transformation of E5 with WT CpSRP43 showed varying degrees of complementation, which was demonstrated by partial recovery of the LHCII proteins to the WT level, and partially restored photosynthetic pigments, photosynthetic ETR, NPQ, and growth, indicating that the V102E mutation was responsible for the reduced LHC in E5.
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8
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Ziehe D, Dünschede B, Schünemann D. From bacteria to chloroplasts: evolution of the chloroplast SRP system. Biol Chem 2017; 398:653-661. [PMID: 28076289 DOI: 10.1515/hsz-2016-0292] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 01/04/2017] [Indexed: 02/02/2023]
Abstract
Chloroplasts derive from a prokaryotic symbiont that lost most of its genes during evolution. As a result, the great majority of chloroplast proteins are encoded in the nucleus and are posttranslationally imported into the organelle. The chloroplast genome encodes only a few proteins. These include several multispan thylakoid membrane proteins which are synthesized on thylakoid-bound ribosomes and cotranslationally inserted into the membrane. During evolution, ancient prokaryotic targeting machineries were adapted and combined with novel targeting mechanisms to facilitate post- and cotranslational protein transport in chloroplasts. This review focusses on the chloroplast signal recognition particle (cpSRP) protein transport system, which has been intensively studied in higher plants. The cpSRP system derived from the prokaryotic SRP pathway, which mediates the cotranslational protein transport to the bacterial plasma membrane. Chloroplasts contain homologs of several components of the bacterial SRP system. The function of these conserved components in post- and/or cotranslational protein transport and chloroplast-specific modifications of these transport mechanisms are described. Furthermore, recent studies of cpSRP systems in algae and lower plants are summarized and their impact on understanding the evolution of the cpSRP system are discussed.
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Affiliation(s)
- Dominik Ziehe
- Molecular Biology of Plant Organelles, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum
| | - Beatrix Dünschede
- Molecular Biology of Plant Organelles, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum
| | - Danja Schünemann
- Molecular Biology of Plant Organelles, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum
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9
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Henderson RC, Gao F, Jayanthi S, Kight A, Sharma P, Goforth RL, Heyes CD, Henry RL, Suresh Kumar TK. Domain Organization in the 54-kDa Subunit of the Chloroplast Signal Recognition Particle. Biophys J 2016; 111:1151-1162. [PMID: 27653474 PMCID: PMC5034345 DOI: 10.1016/j.bpj.2016.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 07/29/2016] [Accepted: 08/02/2016] [Indexed: 10/21/2022] Open
Abstract
Chloroplast signal recognition particle (cpSRP) is a heterodimer composed of an evolutionarily conserved 54-kDa GTPase (cpSRP54) and a unique 43-kDa subunit (cpSRP43) responsible for delivering light-harvesting chlorophyll binding protein to the thylakoid membrane. While a nearly complete three-dimensional structure of cpSRP43 has been determined, no high-resolution structure is yet available for cpSRP54. In this study, we developed and examined an in silico three-dimensional model of the structure of cpSRP54 by homology modeling using cytosolic homologs. Model selection was guided by single-molecule Förster resonance energy transfer experiments, which revealed the presence of at least two distinct conformations. Small angle x-ray scattering showed that the linking region among the GTPase (G-domain) and methionine-rich (M-domain) domains, an M-domain loop, and the cpSRP43 binding C-terminal extension of cpSRP54 are predominantly disordered. Interestingly, the linker and loop segments were observed to play an important role in organizing the domain arrangement of cpSRP54. Further, deletion of the finger loop abolished loading of the cpSRP cargo, light-harvesting chlorophyll binding protein. These data highlight important structural dynamics relevant to cpSRP54's role in the post- and cotranslational signaling processes.
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Affiliation(s)
- Rory C Henderson
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Feng Gao
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Srinivas Jayanthi
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Alicia Kight
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas
| | - Priyanka Sharma
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas
| | - Robyn L Goforth
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas
| | - Colin D Heyes
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Ralph L Henry
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas
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10
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Oryza sativa Chloroplast Signal Recognition Particle 43 (OscpSRP43) Is Required for Chloroplast Development and Photosynthesis. PLoS One 2015; 10:e0143249. [PMID: 26600124 PMCID: PMC4657901 DOI: 10.1371/journal.pone.0143249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/02/2015] [Indexed: 12/26/2022] Open
Abstract
A rice chlorophyll-deficient mutant w67 was isolated from an ethyl methane sulfonate (EMS)-induced IR64 (Oryza sativa L. ssp. indica) mutant bank. The mutant exhibited a distinct yellow-green leaf phenotype in the whole plant growth duration with significantly reduced levels of chlorophyll and carotenoid, impaired chloroplast development and lowered capacity of photosynthesis compared with the wild-type IR64. Expression of a number of genes associated with chlorophyll metabolism, chloroplast biogenesis and photosynthesis was significantly altered in the mutant. Genetic analysis indicated that the yellow-green phenotype was controlled by a single recessive nuclear gene located on the short arm of chromosome 3. Using map-based strategy, the mutation was isolated and predicted to encode a chloroplast signal recognition particle 43 KD protein (cpSRP43) with 388 amino acid residuals. A single base substitution from A to T at position 160 resulted in a premature stop codon. OscpSRP43 was constitutively expressed in various organs with the highest level in the leaf. Functional complementation could rescue the mutant phenotype and subcellular localization showed that the cpSRP43:GFP fusion protein was targeted to the chloroplast. The data suggested that Oryza sativa cpSRP43 (OscpSRP43) was required for the normal development of chloroplasts and photosynthesis in rice.
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11
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Horn A, Hennig J, Ahmed YL, Stier G, Wild K, Sattler M, Sinning I. Structural basis for cpSRP43 chromodomain selectivity and dynamics in Alb3 insertase interaction. Nat Commun 2015; 6:8875. [PMID: 26568381 PMCID: PMC4660199 DOI: 10.1038/ncomms9875] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 10/12/2015] [Indexed: 01/21/2023] Open
Abstract
Canonical membrane protein biogenesis requires co-translational delivery of ribosome-associated proteins to the Sec translocase and depends on the signal recognition particle (SRP) and its receptor (SR). In contrast, high-throughput delivery of abundant light-harvesting chlorophyll a,b-binding proteins (LHCPs) in chloroplasts to the Alb3 insertase occurs post-translationally via a soluble transit complex including the cpSRP43/cpSRP54 heterodimer (cpSRP). Here we describe the molecular mechanisms of tethering cpSRP to the Alb3 insertase by specific interaction of cpSRP43 chromodomain 3 with a linear motif in the Alb3 C-terminal tail. Combining NMR spectroscopy, X-ray crystallography and biochemical analyses, we dissect the structural basis for selectivity of chromodomains 2 and 3 for their respective ligands cpSRP54 and Alb3, respectively. Negative cooperativity in ligand binding can be explained by dynamics in the chromodomain interface. Our study provides a model for membrane recruitment of the transit complex and may serve as a prototype for a functional gain by the tandem arrangement of chromodomains. The chloroplast signal recognition particle delivers LHCPs to the thylakoid membrane by interaction of cpSRP43 with the Alb3 insertase. Here the authors decipher the specific recognition of the Alb3 C-terminal tail within the interface of two communicating chromodomains by structural biochemistry.
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Affiliation(s)
- Annemarie Horn
- Heidelberg University Biochemistry Center (BZH), INF 328, Heidelberg D-69120, Germany
| | - Janosch Hennig
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, Garching DE-85747, Germany.,Institute of Structural Biology, Helmholtz Center Munich, Ingolstädter Landstrasse 1, Neuherberg D-85764, Germany
| | - Yasar L Ahmed
- Heidelberg University Biochemistry Center (BZH), INF 328, Heidelberg D-69120, Germany
| | - Gunter Stier
- Heidelberg University Biochemistry Center (BZH), INF 328, Heidelberg D-69120, Germany
| | - Klemens Wild
- Heidelberg University Biochemistry Center (BZH), INF 328, Heidelberg D-69120, Germany
| | - Michael Sattler
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, Garching DE-85747, Germany.,Institute of Structural Biology, Helmholtz Center Munich, Ingolstädter Landstrasse 1, Neuherberg D-85764, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), INF 328, Heidelberg D-69120, Germany
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12
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Breiman A, Fieulaine S, Meinnel T, Giglione C. The intriguing realm of protein biogenesis: Facing the green co-translational protein maturation networks. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1864:531-50. [PMID: 26555180 DOI: 10.1016/j.bbapap.2015.11.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/05/2015] [Indexed: 01/13/2023]
Abstract
The ribosome is the cell's protein-making factory, a huge protein-RNA complex, that is essential to life. Determining the high-resolution structures of the stable "core" of this factory was among the major breakthroughs of the past decades, and was awarded the Nobel Prize in 2009. Now that the mysteries of the ribosome appear to be more traceable, detailed understanding of the mechanisms that regulate protein synthesis includes not only the well-known steps of initiation, elongation, and termination but also the less comprehended features of the co-translational events associated with the maturation of the nascent chains. The ribosome is a platform for co-translational events affecting the nascent polypeptide, including protein modifications, folding, targeting to various cellular compartments for integration into membrane or translocation, and proteolysis. These events are orchestrated by ribosome-associated protein biogenesis factors (RPBs), a group of a dozen or more factors that act as the "welcoming committee" for the nascent chain as it emerges from the ribosome. In plants these factors have evolved to fit the specificity of different cellular compartments: cytoplasm, mitochondria and chloroplast. This review focuses on the current state of knowledge of these factors and their interaction around the exit tunnel of dedicated ribosomes. Particular attention has been accorded to the plant system, highlighting the similarities and differences with other organisms.
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Affiliation(s)
- Adina Breiman
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France; Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sonia Fieulaine
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France
| | - Thierry Meinnel
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France
| | - Carmela Giglione
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France.
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13
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Trösch R, Töpel M, Flores-Pérez Ú, Jarvis P. Genetic and Physical Interaction Studies Reveal Functional Similarities between ALBINO3 and ALBINO4 in Arabidopsis. PLANT PHYSIOLOGY 2015; 169:1292-306. [PMID: 26265777 PMCID: PMC4587442 DOI: 10.1104/pp.15.00376] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 08/06/2015] [Indexed: 05/20/2023]
Abstract
ALBINO3 (ALB3) is a well-known component of a thylakoid protein-targeting complex that interacts with the chloroplast signal recognition particle (cpSRP) and the cpSRP receptor, chloroplast filamentous temperature-sensitive Y (cpFtsY). Its protein-inserting function has been established mainly for light-harvesting complex proteins, which first interact with the unique chloroplast cpSRP43 component and then are delivered to the ALB3 integrase by a GTP-dependent cpSRP-cpFtsY interaction. In Arabidopsis (Arabidopsis thaliana), a subsequently discovered ALB3 homolog, ALB4, has been proposed to be involved not in light-harvesting complex protein targeting, but instead in the stabilization of the ATP synthase complex. Here, however, we show that ALB3 and ALB4 share significant functional overlap, and that both proteins are required for the efficient insertion of cytochrome f and potentially other subunits of pigment-bearing protein complexes. Genetic and physical interactions between ALB4 and ALB3, and physical interactions between ALB4 and cpSRP, suggest that the two ALB proteins may engage similar sets of interactors for their specific functions. We propose that ALB4 optimizes the insertion of thylakoid proteins by participating in the ALB3-cpSRP pathway for certain substrates (e.g. cytochrome f and the Rieske protein). Although ALB4 has clearly diverged from ALB3 in relation to the partner-recruiting C-terminal domain, our analysis suggests that one putative cpSRP-binding motif has not been entirely lost.
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Affiliation(s)
- Raphael Trösch
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom (R.T., M.T., P.J.); andDepartment of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (U.F.-P., P.J.)
| | - Mats Töpel
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom (R.T., M.T., P.J.); andDepartment of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (U.F.-P., P.J.)
| | - Úrsula Flores-Pérez
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom (R.T., M.T., P.J.); andDepartment of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (U.F.-P., P.J.)
| | - Paul Jarvis
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom (R.T., M.T., P.J.); andDepartment of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (U.F.-P., P.J.)
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14
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Gao F, Kight AD, Henderson R, Jayanthi S, Patel P, Murchison M, Sharma P, Goforth RL, Kumar TKS, Henry RL, Heyes CD. Regulation of Structural Dynamics within a Signal Recognition Particle Promotes Binding of Protein Targeting Substrates. J Biol Chem 2015; 290:15462-15474. [PMID: 25918165 DOI: 10.1074/jbc.m114.624346] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Indexed: 11/06/2022] Open
Abstract
Protein targeting is critical in all living organisms and involves a signal recognition particle (SRP), an SRP receptor, and a translocase. In co-translational targeting, interactions among these proteins are mediated by the ribosome. In chloroplasts, the light-harvesting chlorophyll-binding protein (LHCP) in the thylakoid membrane is targeted post-translationally without a ribosome. A multidomain chloroplast-specific subunit of the SRP, cpSRP43, is proposed to take on the role of coordinating the sequence of targeting events. Here, we demonstrate that cpSRP43 exhibits significant interdomain dynamics that are reduced upon binding its SRP binding partner, cpSRP54. We showed that the affinity of cpSRP43 for the binding motif of LHCP (L18) increases when cpSRP43 is complexed to the binding motif of cpSRP54 (cpSRP54pep). These results support the conclusion that substrate binding to the chloroplast SRP is modulated by protein structural dynamics in which a major role of cpSRP54 is to improve substrate binding efficiency to the cpSRP.
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Affiliation(s)
- Feng Gao
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Alicia D Kight
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | - Rory Henderson
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Srinivas Jayanthi
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Parth Patel
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Marissa Murchison
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Priyanka Sharma
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | - Robyn L Goforth
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | | | - Ralph L Henry
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701.
| | - Colin D Heyes
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701.
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15
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Dünschede B, Träger C, Schröder CV, Ziehe D, Walter B, Funke S, Hofmann E, Schünemann D. Chloroplast SRP54 Was Recruited for Posttranslational Protein Transport via Complex Formation with Chloroplast SRP43 during Land Plant Evolution. J Biol Chem 2015; 290:13104-14. [PMID: 25833951 DOI: 10.1074/jbc.m114.597922] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Indexed: 01/05/2023] Open
Abstract
In bacteria, membrane proteins are targeted cotranslationally via a signal recognition particle (SRP). During the evolution of higher plant chloroplasts from cyanobacteria, the SRP pathway underwent striking adaptations that enable the posttranslational transport of the abundant light-harvesting chlorophyll-a/b-binding proteins (LHCPs). The conserved 54-kDa SRP subunit in higher plant chloroplasts (cpSRP54) is not bound to an SRP RNA, an essential SRP component in bacteria, but forms a stable heterodimer with the chloroplast-specific cpSRP43. This heterodimeric cpSRP recognizes LHCP and delivers it to the thylakoid membrane whereby cpSRP43 plays a central role. This study shows that the cpSRP system in the green alga Chlamydomonas reinhardtii differs significantly from that of higher plants as cpSRP43 is not complexed to cpSRP54 in Chlamydomonas and cpSRP54 is not involved in LHCP recognition. This divergence is attributed to altered residues within the cpSRP54 tail and the second chromodomain of cpSRP43 that are crucial for the formation of the binding interface in Arabidopsis. These changes are highly conserved among chlorophytes, whereas all land plants contain cpSRP proteins with typical interaction motifs. These data demonstrate that the coevolution of LHCPs and cpSRP43 occurred independently of complex formation with cpSRP54 and that the interaction between cpSRP54 and cpSRP43 evolved later during the transition from chlorophytes to land plants. Furthermore, our data show that in higher plants a heterodimeric form of cpSRP is required for the formation of a low molecular weight transit complex with LHCP.
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Affiliation(s)
| | | | | | | | - Björn Walter
- From the Molecular Biology of Plant Organelles and
| | - Silke Funke
- From the Molecular Biology of Plant Organelles and
| | - Eckhard Hofmann
- Protein Crystallography, Ruhr University Bochum, 44780 Bochum, Germany
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16
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Nguyen TX, Jaru-Ampornpan P, Lam VQ, Cao P, Piszkiewicz S, Hess S, Shan SO. Mechanism of an ATP-independent protein disaggregase: I. structure of a membrane protein aggregate reveals a mechanism of recognition by its chaperone. J Biol Chem 2013; 288:13420-30. [PMID: 23525109 DOI: 10.1074/jbc.m113.462812] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND A novel chaperone, cpSRP43, recognizes and disassembles the aggregates formed by its client proteins. RESULTS The client proteins of cpSRP43 form stable disc-shaped aggregates with the chaperone recognition motif displayed onthe surface. CONCLUSION The surface-exposed motif on the aggregate allows it to be recognized by its chaperone. SIGNIFICANCE Understanding the structure and energetics of protein aggregates provides insights into the mechanism of theirDISASSEMBLY.Protein aggregation is detrimental to the maintenance of proper protein homeostasis in all cells. To overcome this problem, cells have evolved a network of molecular chaperones to prevent protein aggregation and even reverse existing protein aggregates. The most extensively studied disaggregase systems are ATP-driven macromolecular machines. Recently, we reported an alternative disaggregase system in which the 38-kDa subunit of chloroplast signal recognition particle (cpSRP43) efficiently reverses the aggregation of its substrates, the light-harvesting chlorophyll a/b-binding (LHC) proteins, in the absence of external energy input. To understand the molecular mechanism of this novel activity, here we used biophysical and biochemical methods to characterize the structure and nature of LHC protein aggregates. We show that LHC proteins form micellar, disc-shaped aggregates that are kinetically stable and detergent-resistant. Despite the nonamyloidal nature, the LHC aggregates have a defined global organization, displaying the chaperone recognition motif on its solvent-accessible surface. These findings suggest an attractive mechanism for recognition of the LHC aggregate by cpSRP43 and provide important constraints to define the capability of this chaperone.
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Affiliation(s)
- Thang X Nguyen
- Division of Chemistry and Chemical Engineering, Beckman Institute, California Institute of Technology, Pasadena, California 91125, USA
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17
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Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43-substrate interaction domain. Biochem J 2011; 437:149-55. [PMID: 21466505 DOI: 10.1042/bj20110270] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A cpSRP [chloroplast SRP (signal recognition particle)] comprising cpSRP54 and cpSRP43 subunits mediates the insertion of light-harvesting proteins into the thylakoid membrane. We dissected its interaction with a full-length membrane protein substrate in aqueous solution by insertion of site-specific photo-activatable cross-linkers into in vitro-synthesized Lhcb1 (major light-harvesting chlorophyll-binding protein of photosystem II). We show that Lhcb1 residues 166-176 cross-link specifically to the cpSRP43 subunit. Some cross-link positions within Lhcb1 are in the 'L18' peptide required for targeting of cpSRP substrates, whereas other cross-linking positions define a new targeting signal in the third transmembrane span. Lhcb1 was not found to cross-link to cpSRP54 at any position, and cross-linking to cpSRP43 is unaffected by the absence of cpSRP54. cpSRP43 thus effectively binds substrates autonomously, and its ability to independently bind an extended 20+-residue substrate region highlights a major difference with other SRP types where the SRP54 subunit binds to hydrophobic target sequences. The results also show that cpSRP43 can bind to a hydrophobic, three-membrane span, substrate in aqueous solution, presumably reflecting a role for cpSRP in the chloroplast stroma. This mode of action, and the specificity of the cpSRP43-substrate interaction, may be associated with cpSRP's unique post-translational mode of action.
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18
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Dünschede B, Bals T, Funke S, Schünemann D. Interaction studies between the chloroplast signal recognition particle subunit cpSRP43 and the full-length translocase Alb3 reveal a membrane-embedded binding region in Alb3 protein. J Biol Chem 2011; 286:35187-95. [PMID: 21832051 DOI: 10.1074/jbc.m111.250746] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Posttranslational targeting of the light-harvesting chlorophyll a,b-binding proteins depends on the function of the chloroplast signal recognition particle, its receptor cpFtsY, and the translocase Alb3. The thylakoid membrane protein Alb3 of Arabidopsis chloroplasts belongs to the evolutionarily conserved YidC/Oxa1/Alb3 protein family; the members of this family facilitate the insertion, folding, and assembly of membrane proteins in bacteria, mitochondria, and chloroplasts. Here, we analyzed the interaction sites of full-length Alb3 with the cpSRP pathway component cpSRP43 by using in vitro and in vivo studies. Bimolecular fluorescence complementation and Alb3 proteoliposome studies showed that the interaction of cpSRP43 is dependent on a binding domain in the C terminus of Alb3 as well as an additional membrane-embedded binding site in the fifth transmembrane domain (TMD5) of Alb3. The C-terminal binding domain was mapped to residues 374-388, and the binding domain within TMD5 was mapped to residues 314-318 located close to the luminal end of TMD5. A direct binding between cpSRP43 and these binding motifs was shown by pepspot analysis. Further studies using blue-native gel electrophoresis revealed that full-length Alb3 is able to form dimers. This finding and the identification of a membrane-embedded cpSRP43 binding site in Alb3 support a model in which cpSRP43 inserts into a dimeric Alb3 translocation pore during cpSRP-dependent delivery of light-harvesting chlorophyll a,b-binding proteins.
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Affiliation(s)
- Beatrix Dünschede
- Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780 Bochum, Germany
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19
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LTD is a protein required for sorting light-harvesting chlorophyll-binding proteins to the chloroplast SRP pathway. Nat Commun 2011; 2:277. [DOI: 10.1038/ncomms1278] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 03/16/2011] [Indexed: 11/08/2022] Open
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20
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Lewis NE, Marty NJ, Kathir KM, Rajalingam D, Kight AD, Daily A, Kumar TKS, Henry RL, Goforth RL. A dynamic cpSRP43-Albino3 interaction mediates translocase regulation of chloroplast signal recognition particle (cpSRP)-targeting components. J Biol Chem 2010; 285:34220-30. [PMID: 20729200 PMCID: PMC2962520 DOI: 10.1074/jbc.m110.160093] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 08/16/2010] [Indexed: 12/31/2022] Open
Abstract
The chloroplast signal recognition particle (cpSRP) and its receptor, chloroplast FtsY (cpFtsY), form an essential complex with the translocase Albino3 (Alb3) during post-translational targeting of light-harvesting chlorophyll-binding proteins (LHCPs). Here, we describe a combination of studies that explore the binding interface and functional role of a previously identified cpSRP43-Alb3 interaction. Using recombinant proteins corresponding to the C terminus of Alb3 (Alb3-Cterm) and various domains of cpSRP43, we identify the ankyrin repeat region of cpSRP43 as the domain primarily responsible for the interaction with Alb3-Cterm. Furthermore, we show Alb3-Cterm dissociates a cpSRP·LHCP targeting complex in vitro and stimulates GTP hydrolysis by cpSRP54 and cpFtsY in a strictly cpSRP43-dependent manner. These results support a model in which interactions between the ankyrin region of cpSRP43 and the C terminus of Alb3 promote distinct membrane-localized events, including LHCP release from cpSRP and release of targeting components from Alb3.
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Affiliation(s)
| | | | | | | | | | - Anna Daily
- Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
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21
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Wang P, Dalbey RE. Inserting membrane proteins: the YidC/Oxa1/Alb3 machinery in bacteria, mitochondria, and chloroplasts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:866-75. [PMID: 20800571 DOI: 10.1016/j.bbamem.2010.08.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 08/18/2010] [Accepted: 08/20/2010] [Indexed: 10/19/2022]
Abstract
The evolutionarily conserved YidC/Oxa1p/Alb3 family of proteins plays important roles in the membrane biogenesis in bacteria, mitochondria, and chloroplasts. The members in this family function as novel membrane protein insertases, chaperones, and assembly factors for transmembrane proteins, including energy transduction complexes localized in the bacterial and mitochondrial inner membrane, and in the chloroplast thylakoid membrane. In this review, we will present recent progress with this class of proteins in membrane protein biogenesis and discuss the structure/function relationships. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Peng Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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22
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Component interactions, regulation and mechanisms of chloroplast signal recognition particle-dependent protein transport. Eur J Cell Biol 2010; 89:965-73. [PMID: 20709425 DOI: 10.1016/j.ejcb.2010.06.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The chloroplast proteome comprises nuclear- and plastome-encoded proteins. In order to function correctly these proteins must be transported, either cotranslationally or posttranslationally, to their final destination in the chloroplast. Here the chloroplast signal recognition particle (cpSRP) which is present in two different stromal pools plays an essential role. On the one hand, the conserved 54kDa subunit (cpSRP54) is associated with 70S ribosomes to function in the cotranslational transport of the plastid-encoded thylakoid membrane protein D1. On the other hand, the cpSRP consists of cpSRP54 and a unique 43kDa subunit (cpSRP43) and facilitates the transport of nuclear-encoded light-harvesting chlorophyll-binding proteins (LHCPs), the most abundant membrane proteins of the thylakoids. In addition to cpSRP, the cpSRP receptor cpFtsY and the thylakoid membrane protein Alb3 are required for posttranslational LHCP integration in a GTP-dependent manner. In contrast to the universally conserved cytosolic SRP, the chloroplast SRP of higher plants lacks an SRP-RNA component. Interestingly, cpSRP-RNA genes have been identified in the plastome of lower plants, indicating that their cpSRP structure resembles the cytosolic SRP.
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23
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Jaru-Ampornpan P, Shen K, Lam VQ, Ali M, Doniach S, Jia TZ, Shan SO. ATP-independent reversal of a membrane protein aggregate by a chloroplast SRP subunit. Nat Struct Mol Biol 2010; 17:696-702. [PMID: 20424608 PMCID: PMC2917185 DOI: 10.1038/nsmb.1836] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 04/20/2010] [Indexed: 02/06/2023]
Abstract
Membrane proteins impose enormous challenges to cellular protein homeostasis during their post-translational targeting, and they require chaperones to keep them soluble and translocation competent. Here we show that a novel targeting factor in the chloroplast signal recognition particle (cpSRP), cpSRP43, is a highly specific molecular chaperone that efficiently reverses the aggregation of its substrate proteins. In contrast to 'ATPases associated with various cellular activities' (AAA(+)) chaperones, cpSRP43 uses specific binding interactions with its substrate to mediate its 'disaggregase' activity. This disaggregase capability can allow targeting machineries to more effectively capture their protein substrates and emphasizes a close connection between protein folding and trafficking processes. Moreover, cpSRP43 provides the first example to our knowledge of an ATP-independent disaggregase and shows that efficient reversal of protein aggregation can be attained by specific binding interactions between a chaperone and its substrate.
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Affiliation(s)
- Peera Jaru-Ampornpan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
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24
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Falk S, Sinning I. cpSRP43 is a novel chaperone specific for light-harvesting chlorophyll a,b-binding proteins. J Biol Chem 2010; 285:21655-61. [PMID: 20498370 PMCID: PMC2898393 DOI: 10.1074/jbc.c110.132746] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The biosynthesis of most membrane proteins is directly coupled to membrane insertion, and therefore, molecular chaperones are not required. The light-harvesting chlorophyll a,b-binding proteins (LHCPs) present a prominent exception as they are synthesized in the cytoplasm, and after import into the chloroplast, they are targeted and inserted into the thylakoid membrane. Upon arrival in the stroma, LHCPs form a soluble transit complex with the chloroplast signal recognition particle (cpSRP) consisting of an SRP54 homolog and the unique cpSRP43 composed of three chromodomains and four ankyrin repeats. Here we describe that cpSRP43 alone prevents aggregation of LHCP by formation of a complex with nanomolar affinity, whereas cpSRP54 is not required for this chaperone activity. Other stromal chaperones like trigger factor cannot replace cpSRP43, which implies that LHCPs require a specific chaperone. Although cpSRP43 does not have an ATPase activity, it can dissolve aggregates of LHCPs similar to chaperones of the Hsp104/ClpB family. We show that the LHCP-cpSRP43 interaction is predominantly hydrophobic but strictly depends on an intact DPLG motif between the second and third transmembrane region. The cpSRP43 ankyrin repeats that provide the binding site for the DPLG motif are sufficient for the chaperone function, whereas the chromodomains are dispensable. Taken together, we define cpSRP43 as a highly specific chaperone for LHCPs in addition to its established function as a targeting factor for this family of membrane proteins.
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Affiliation(s)
- Sebastian Falk
- Heidelberg University Biochemistry Center BZH, INF 328, D-69120 Heidelberg, Germany
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25
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Falk S, Ravaud S, Koch J, Sinning I. The C terminus of the Alb3 membrane insertase recruits cpSRP43 to the thylakoid membrane. J Biol Chem 2009; 285:5954-62. [PMID: 20018841 DOI: 10.1074/jbc.m109.084996] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The YidC/Oxa1/Alb3 family of membrane proteins controls the insertion and assembly of membrane proteins in bacteria, mitochondria, and chloroplasts. Here we describe the molecular mechanisms underlying the interaction of Alb3 with the chloroplast signal recognition particle (cpSRP). The Alb3 C-terminal domain (A3CT) is intrinsically disordered and recruits cpSRP to the thylakoid membrane by a coupled binding and folding mechanism. Two conserved, positively charged motifs reminiscent of chromodomain interaction motifs in histone tails are identified in A3CT that are essential for the Alb3-cpSRP43 interaction. They are absent in the C-terminal domain of Alb4, which therefore does not interact with cpSRP43. Chromodomain 2 in cpSRP43 appears as a central binding platform that can interact simultaneously with A3CT and cpSRP54. The observed negative cooperativity of the two binding events provides the first insights into cargo release at the thylakoid membrane. Taken together, our data show how Alb3 participates in cpSRP-dependent membrane targeting, and our data provide a molecular explanation why Alb4 cannot compensate for the loss of Alb3. Oxa1 and YidC utilize their positively charged, C-terminal domains for ribosome interaction in co-translational targeting. Alb3 is adapted for the chloroplast-specific Alb3-cpSRP43 interaction in post-translational targeting by extending the spectrum of chromodomain interactions.
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Affiliation(s)
- Sebastian Falk
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
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26
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Abstract
The Signal Recognition Particle (SRP) plays a critical role in the sorting of nascent secretory and membrane proteins. Remarkably, this function has been conserved from bacteria, where SRP delivers proteins to the inner membrane, through to eukaryotes, where SRP is required for targeting of proteins to the endoplasmic reticulum. This review focuses on present understanding of SRP structure and function and the relationship between the two. Furthermore, the similarities and differences in the structure, function and cellular role of SRP in bacteria, chloroplasts, fungi and mammals will be stressed.
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Affiliation(s)
- Martin R Pool
- Faculty of Life Sciences, University of Manchester, Manchester, UK.
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27
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Jaru-Ampornpan P, Nguyen TX, Shan SO. A distinct mechanism to achieve efficient signal recognition particle (SRP)-SRP receptor interaction by the chloroplast srp pathway. Mol Biol Cell 2009; 20:3965-73. [PMID: 19587121 DOI: 10.1091/mbc.e08-10-0989] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cotranslational protein targeting by the signal recognition particle (SRP) requires the SRP RNA, which accelerates the interaction between the SRP and SRP receptor 200-fold. This otherwise universally conserved SRP RNA is missing in the chloroplast SRP (cpSRP) pathway. Instead, the cpSRP and cpSRP receptor (cpFtsY) by themselves can interact 200-fold faster than their bacterial homologues. Here, cross-complementation analyses revealed the molecular origin underlying their efficient interaction. We found that cpFtsY is 5- to 10-fold more efficient than Escherichia coli FtsY at interacting with the GTPase domain of SRP from both chloroplast and bacteria, suggesting that cpFtsY is preorganized into a conformation more conducive to complex formation. Furthermore, the cargo-binding M-domain of cpSRP provides an additional 100-fold acceleration for the interaction between the chloroplast GTPases, functionally mimicking the effect of the SRP RNA in the cotranslational targeting pathway. The stimulatory effect of the SRP RNA or the M-domain of cpSRP is specific to the homologous SRP receptor in each pathway. These results strongly suggest that the M-domain of SRP actively communicates with the SRP and SR GTPases and that the cytosolic and chloroplast SRP pathways have evolved distinct molecular mechanisms (RNA vs. protein) to mediate this communication.
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Affiliation(s)
- Peera Jaru-Ampornpan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract
Correct protein function depends on delivery to the appropriate cellular or subcellular compartment. Following the initiation of protein synthesis in the cytosol, many bacterial and eukaryotic proteins must be integrated into or transported across a membrane to reach their site of function. Whereas in the post-translational delivery pathway ATP-dependent factors bind to completed polypeptides and chaperone them until membrane translocation is initiated, a GTP-dependent co-translational pathway operates to couple ongoing protein synthesis to membrane transport. These distinct pathways provide different solutions for the maintenance of proteins in a state that is competent for membrane translocation and their delivery for export from the cytosol.
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Richter CV, Träger C, Schünemann D. Evolutionary substitution of two amino acids in chloroplast SRP54 of higher plants cause its inability to bind SRP RNA. FEBS Lett 2008; 582:3223-9. [PMID: 18755190 DOI: 10.1016/j.febslet.2008.08.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 08/14/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
The chloroplast signal recognition particle (cpSRP) consists of a conserved 54 kDa subunit (cpSRP54) and a unique 43 kDa subunit (cpSRP43) but lacks SRP-RNA, an essential and universally conserved component of cytosolic SRPs. High sequence similarity exists between cpSRP54 and bacterial SRP54 except for a plant-specific C-terminal extension containing the cpSRP43-binding motif. We found that cpSRP54 of higher plants lacks the ability to bind SRP-RNA because of two amino acid substitutions within a region corresponding to the RNA binding domain of cytosolic SRP54, whereas the C-terminal extension does not affect RNA binding. Phylogenetic analysis revealed that these mutations occur in the cpSRP54 homologues of higher plants but not in most algae.
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Affiliation(s)
- Christine V Richter
- Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, 44780 Bochum, Germany
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31
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Radzimanowski J, Ravaud S, Schlesinger S, Koch J, Beyreuther K, Sinning I, Wild K. Crystal Structure of the Human Fe65-PTB1 Domain. J Biol Chem 2008; 283:23113-20. [DOI: 10.1074/jbc.m800861200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Stengel KF, Holdermann I, Cain P, Robinson C, Wild K, Sinning I. Structural basis for specific substrate recognition by the chloroplast signal recognition particle protein cpSRP43. Science 2008; 321:253-6. [PMID: 18621669 DOI: 10.1126/science.1158640] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Secretory and membrane proteins carry amino-terminal signal sequences that, in cotranslational targeting, are recognized by the signal recognition particle protein SRP54 without sequence specificity. The most abundant membrane proteins on Earth are the light-harvesting chlorophyll a/b binding proteins (LHCPs). They are synthesized in the cytoplasm, imported into the chloroplast, and posttranslationally targeted to the thylakoid membrane by cpSRP, a heterodimer formed by cpSRP54 and cpSRP43. We present the 1.5 angstrom crystal structure of cpSRP43 characterized by a unique arrangement of chromodomains and ankyrin repeats. The overall shape and charge distribution of cpSRP43 resembles the SRP RNA, which is absent in chloroplasts. The complex with the internal signal sequence of LHCPs reveals that cpSRP43 specifically recognizes a DPLG peptide motif. We describe how cpSPR43 adapts the universally conserved SRP system to posttranslational targeting and insertion of the LHCP family of membrane proteins.
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Affiliation(s)
- Katharina F Stengel
- Biochemie-Zentrum der Universität Heidelberg, INF328, D-69120 Heidelberg, Germany
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33
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Kathir KM, Rajalingam D, Sivaraja V, Kight A, Goforth RL, Yu C, Henry R, Kumar TKS. Assembly of chloroplast signal recognition particle involves structural rearrangement in cpSRP43. J Mol Biol 2008; 381:49-60. [PMID: 18586266 DOI: 10.1016/j.jmb.2008.05.065] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 05/27/2008] [Accepted: 05/27/2008] [Indexed: 10/22/2022]
Abstract
Signal recognition particle in chloroplasts (cpSRP) exhibits the unusual ability to bind and target full-length proteins to the thylakoid membrane. Unlike cytosolic SRPs in prokaryotes and eukaryotes, cpSRP lacks an RNA moiety and functions as a heterodimer composed of a conserved 54-kDa guanosine triphosphatase (cpSRP54) and a unique 43-kDa subunit (cpSRP43). Assembly of the cpSRP heterodimer is a prerequisite for post-translational targeting activities and takes place through interactions between chromatin modifier domain 2 (CD2) of cpSRP43 and a unique 10-amino-acid region in cpSRP54 (cpSRP54(pep)). We have used multidimensional NMR spectroscopy and other biophysical methods to examine the assembly and structure of the cpSRP43-cpSRP54 interface. Our data show that CD2 of cpSRP43 binds to cpSRP54(pep) in a 1:1 stoichiometry with an apparent K(d) of approximately 1.06 muM. Steady-state fluorescence and far-UV circular dichroism data suggest that the CD2-cpSRP54(pep) interaction causes significant conformational changes in both CD2 and the peptide. Comparison of the three-dimensional solution structures of CD2 alone and in complex with cpSRP54(pep) shows that significant structural changes are induced in CD2 in order to establish a binding interface contributed mostly by residues in the N-terminal segment of CD2 (Phe5-Val10) and an arginine doublet (Arg536 and Arg537) in the cpSRP54 peptide. Taken together, our results provide new insights into the mechanism of cpSRP assembly and the structural forces that stabilize the functionally critical cpSRP43-cpSRP54 interaction.
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Ananthamurthy K, Kathir KM, Kumar TKS, Kight A, Goforth RL, Henry R. H, C and N resonance assignments of the C-terminal domain of the 43 kDa subunit of the chloroplast signal recognition particle. BIOMOLECULAR NMR ASSIGNMENTS 2008; 2:37-39. [PMID: 19112521 PMCID: PMC2609747 DOI: 10.1007/s12104-007-9078-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the assignment of a 109 amino acid C-terminal chromo domain of the chloroplast signal recognition particle cpSRP43 subunit. cpSRP43 plays a crucial role in the targeting of light harvesting chlorophyll proteins to the thylakoids.
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35
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Hernández Torres J, Maldonado MAA, Chomilier J. Tandem duplications of a degenerated GTP-binding domain at the origin of GTPase receptors Toc159 and thylakoidal SRP. Biochem Biophys Res Commun 2007; 364:325-31. [PMID: 17950698 DOI: 10.1016/j.bbrc.2007.10.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 10/03/2007] [Indexed: 11/28/2022]
Abstract
The evolutionary origin of some nuclear encoded proteins that translocate proteins across the chloroplast envelope remains unknown. Therefore, sequences of GTPase proteins constituting the Arabidopsis thaliana translocon at the outer membrane of chloroplast (atToc) complexes were analyzed by means of HCA. In particular, atToc159 and related proteins (atToc132, atToc120, and atToc90) do not have proven homologues of prokaryotic or eukaryotic ancestry. We established that the three domains commonly referred to as A, G, and M originate from the GTPase G domain, tandemly repeated, and probably evolving toward an unstructured conformation in the case of the A domain. It resulted from this study a putative common ancestor for these proteins and a new domain definition, in particular the splitting of A into three domains (A1, A2, and A3), has been proposed. The family of Toc159, previously containing A. thaliana and Pisum sativum, has been extended to Medicago truncatula and Populus trichocarpa and it has been revised for Oryza sativa. They have also been compared to GTPase subunits involved in the cpSRP system. A distant homology has been revealed among Toc and cpSRP GTP-hydrolyzing proteins of A. thaliana, and repetitions of a GTPase domain were also found in cpSRP protein receptors, by means of HCA analysis.
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Affiliation(s)
- Jorge Hernández Torres
- Laboratorio de Biología Molecular, CINBIN, Universidad Industrial de Santander, Bucaramanga, Apartado Aéreo 678, Colombia.
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36
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The structure of the chloroplast signal recognition particle (SRP) receptor reveals mechanistic details of SRP GTPase activation and a conserved membrane targeting site. FEBS Lett 2007; 581:5671-6. [DOI: 10.1016/j.febslet.2007.11.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 11/07/2007] [Accepted: 11/08/2007] [Indexed: 11/19/2022]
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37
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Marín-Navarro J, Manuell AL, Wu J, P Mayfield S. Chloroplast translation regulation. PHOTOSYNTHESIS RESEARCH 2007; 94:359-74. [PMID: 17661159 DOI: 10.1007/s11120-007-9183-z] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 04/19/2007] [Indexed: 05/16/2023]
Abstract
Chloroplast gene expression is primarily controlled during the translation of plastid mRNAs. Translation is regulated in response to a variety of biotic and abiotic factors, and requires a coordinate expression with the nuclear genome. The translational apparatus of chloroplasts is related to that of bacteria, but has adopted novel mechanisms in order to execute the specific roles that this organelle performs within a eukaryotic cell. Accordingly, plastid ribosomes contain a number of chloroplast-unique proteins and domains that may function in translational regulation. Chloroplast translation regulation involves cis-acting RNA elements (located in the mRNA 5' UTR) as well as a set of corresponding trans-acting protein factors. While regulation of chloroplast translation is primarily controlled at the initiation steps through these RNA-protein interactions, elongation steps are also targets for modulating chloroplast gene expression. Translation of chloroplast mRNAs is regulated in response to light, and the molecular mechanisms underlying this response involve changes in the redox state of key elements related to the photosynthetic electron chain, fluctuations of the ADP/ATP ratio and the generation of a proton gradient. Photosynthetic complexes also experience assembly-related autoinhibition of translation to coordinate the expression of different subunits of the same complex. Finally, the localization of all these molecular events among the different chloroplast subcompartments appear to be a crucial component of the regulatory mechanisms of chloroplast gene expression.
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Affiliation(s)
- Julia Marín-Navarro
- Department of Cell Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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38
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Tzvetkova-Chevolleau T, Hutin C, Noël LD, Goforth R, Carde JP, Caffarri S, Sinning I, Groves M, Teulon JM, Hoffman NE, Henry R, Havaux M, Nussaume L. Canonical signal recognition particle components can be bypassed for posttranslational protein targeting in chloroplasts. THE PLANT CELL 2007; 19:1635-48. [PMID: 17513500 PMCID: PMC1913721 DOI: 10.1105/tpc.106.048959] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The chloroplast signal recognition particle (cpSRP) and its receptor (cpFtsY) target proteins both cotranslationally and posttranslationally to the thylakoids. This dual function enables cpSRP to utilize its posttranslational activities for targeting a family of nucleus-encoded light-harvesting chlorophyll binding proteins (LHCPs), the most abundant membrane proteins in plants. Previous in vitro experiments indicated an absolute requirement for all cpSRP pathway soluble components. In agreement, a cpFtsY mutant in Arabidopsis thaliana exhibits a severe chlorotic phenotype resulting from a massive loss of LHCPs. Surprisingly, a double mutant, cpftsy cpsrp54, recovers to a great extent from the chlorotic cpftsy phenotype. This establishes that in plants, a new alternative pathway exists that can bypass cpSRP posttranslational targeting activities. Using a mutant form of cpSRP43 that is unable to assemble with cpSRP54, we complemented the cpSRP43-deficient mutant and found that this subunit is required for the alternative pathway. Along with the ability of cpSRP43 alone to bind the ALBINO3 translocase required for LHCP integration, our results indicate that cpSRP43 has developed features to function independently of cpSRP54/cpFtsY in targeting LHCPs to the thylakoid membranes.
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Affiliation(s)
- Tzvetelina Tzvetkova-Chevolleau
- Direction des Sciences du Vivant, Institut de Biologie Environementale et de Biotechnologie, Service de Biologie Végétale et de Microbiologie Environementale, Commissariat à l'Energie Atomique Cadarache, F-13108 Saint-Paul-lez-Durance Cedex, France
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39
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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.
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Affiliation(s)
- Danja Schünemann
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
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40
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Hilpert K, Winkler DFH, Hancock REW. Cellulose-bound Peptide Arrays: Preparation and Applications. Biotechnol Genet Eng Rev 2007; 24:31-106. [DOI: 10.1080/02648725.2007.10648093] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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41
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van der Sluis EO, Nouwen N, Koch J, de Keyzer J, van der Does C, Tampé R, Driessen AJM. Identification of Two Interaction Sites in SecY that Are Important for the Functional Interaction with SecA. J Mol Biol 2006; 361:839-49. [PMID: 16890955 DOI: 10.1016/j.jmb.2006.07.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 07/03/2006] [Accepted: 07/12/2006] [Indexed: 11/24/2022]
Abstract
The motor protein SecA drives the translocation of (pre-)proteins across the SecYEG channel in the bacterial cytoplasmic membrane by nucleotide-dependent cycles of conformational changes often referred to as membrane insertion/de-insertion. Despite structural data on SecA and an archaeal homolog of SecYEG, the identity of the sites of interaction between SecA and SecYEG are unknown. Here, we show that SecA can be cross-linked to several residues in cytoplasmic loop 5 (C5) of SecY, and that SecA directly interacts with a part of transmembrane segment 4 (TMS4) of SecY that is buried in the membrane region of SecYEG. Mutagenesis of either the conserved Arg357 in C5 or Glu176 in TMS4 interferes with the catalytic activity of SecA but not with binding of SecA to SecYEG. Our data explain how conformational changes in SecA could be directly coupled to the previously proposed opening mechanism of the SecYEG channel.
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Affiliation(s)
- Eli O van der Sluis
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9751 NN Haren, The Netherlands
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42
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Sivaraja V, Kumar TKS, Leena PST, Chang AN, Vidya C, Goforth RL, Rajalingam D, Arvind K, Ye JL, Chou J, Henry R, Yu C. Three-dimensional solution structures of the chromodomains of cpSRP43. J Biol Chem 2005; 280:41465-71. [PMID: 16183644 DOI: 10.1074/jbc.m507077200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chloroplasts contain a unique signal recognition particle (cpSRP). Unlike the cytoplasmic forms, the cpSRP lacks RNA but contains a conserved 54-kDa GTPase and a novel 43-kDa subunit (cpSRP43). Recently, three functionally distinct chromodomains (CDs) have been identified in cpSRP43. In the present study, we report the three-dimensional solution structures of the three CDs (CD1, CD2, and CD3) using a variety of triple resonance NMR experiments. The structure of CD1 consists of a triple-stranded beta-sheet segment. The C-terminal helical segment typically found in the nuclear chromodomains is absent in CD1. The secondary structural elements in CD2 and CD3 include a triple-stranded antiparallel beta-sheet and a C-terminal helix. Interestingly, the orientation of the C-terminal helix is significantly different in the structures of CD2 and CD3. Critical comparison of the structures of the chromodomains of cpSRP43 with those found in nuclear chromodomain proteins revealed that the diverse protein-protein interactions mediated by the CDs appear to stem from the differences that exist in the surface charge potentials of each CD. Results of isothermal titration calorimetry experiments confirmed that only CD2 is involved in binding to cpSRP54. The negatively charged C-terminal helix in CD2 possibly plays a crucial role in the cpSRP54-cpSRP43 interaction.
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Affiliation(s)
- Vaithiyalingam Sivaraja
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA
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43
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Funke S, Knechten T, Ollesch J, Schünemann D. A unique sequence motif in the 54-kDa subunit of the chloroplast signal recognition particle mediates binding to the 43-kDa subunit. J Biol Chem 2005; 280:8912-7. [PMID: 15632183 DOI: 10.1074/jbc.m409992200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chloroplasts contain a novel type of signal recognition particle (cpSRP) that consists of two proteins, cpSRP54 and cpSRP43. cpSRP is involved in the post-translational targeting of the nuclear encoded light-harvesting chlorophyll-binding proteins (LHCPs) to the thylakoid membrane by forming a soluble cpSRP.LHCP transit complex in the stroma. Despite high sequence homology between chloroplast and cytosolic SRP54 proteins, the 54-kDa subunit of cpSRP is unique in its ability to bind cpSRP43. In this report, we identified a 10-amino acid long segment of cpSRP54 that forms the cpSRP43-binding site. This segment is located at position 530-539 close to the C terminus of cpSRP54. In addition, we demonstrate that arginine at position 537 is essential for binding cpSRP43 and that mutation of arginine 536 drastically reduced cpSRP43 binding. Mutations within the cpSRP43-binding site of cpSRP54 that reduced or completely abolished cpSRP complex formation also did inhibit transit complex formation and integration of LHCP into the thylakoid membrane, reflecting the importance of these residues for LHCP targeting. Alignment studies revealed that the cpSRP43-binding site is conserved in chloroplast SRP54 proteins and is not present in any SRP54 subunit of cytosolic SRPs.
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Affiliation(s)
- Silke Funke
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, 44780 Bochum, Germany
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44
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Rosenblad MA, Samuelsson T. Identification of chloroplast signal recognition particle RNA genes. PLANT & CELL PHYSIOLOGY 2004; 45:1633-1639. [PMID: 15574839 DOI: 10.1093/pcp/pch185] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The signal recognition particle (SRP) is a ribonucleoprotein complex responsible for targeting proteins to the ER membrane in eukaryotes, the plasma membrane in bacteria and the thylakoid membrane in chloroplasts. In higher plants two different SRP-dependent mechanisms have been identified: one post-translational for proteins imported to the chloroplast and one co-translational for proteins encoded by the plastid genome. The post-translational chloroplast SRP (cpSRP) consists of the protein subunits cpSRP54 and cpSRP43. An RNA component has not been identified and does not seem to be required for the post-translational cpSRP. The co-translational mechanism is known to involve cpSRP54, but an RNA component has not yet been identified. Several chloroplast genomes have been sequenced recently, making a phylogenetically broad computational search for cpSRP RNA possible. We have analysed chloroplast genomes from 27 organisms. In higher plant chloroplasts, no SRP RNA genes were identified. However, eight plastids from red algae and Chlorophyta were found to contain an SRP RNA gene. These results suggest that SRP RNA forms a complex in these plastids with cpSRP54, reminiscent of the eubacterial SRP.
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Affiliation(s)
- Magnus Alm Rosenblad
- Department of Medical Biochemistry, Goteborg University, Box 440, SE-405 30 Goteborg, Sweden
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45
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Abstract
The signal recognition particle (SRP) directs integral membrane and secretory proteins to the cellular protein translocation machinery during translation. The SRP is an evolutionarily conserved RNA-protein complex whose activities are regulated by GTP hydrolysis. Recent structural investigations of SRP functional domains and interactions provide new insights into the mechanisms of SRP activity in all cells, leading toward a comprehensive understanding of protein trafficking by this elegant pathway.
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Affiliation(s)
- Jennifer A Doudna
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California 94705, USA.
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46
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Goforth RL, Peterson EC, Yuan J, Moore MJ, Kight AD, Lohse MB, Sakon J, Henry RL. Regulation of the GTPase cycle in post-translational signal recognition particle-based protein targeting involves cpSRP43. J Biol Chem 2004; 279:43077-84. [PMID: 15292240 DOI: 10.1074/jbc.m401600200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chloroplast signal recognition particle consists of a conserved 54-kDa GTPase and a novel 43-kDa chromodomain protein (cpSRP43) that together bind light-harvesting chlorophyll a/b-binding protein (LHCP) to form a soluble targeting complex that is subsequently directed to the thylakoid membrane. Homology-based modeling of cpSRP43 indicates the presence of two previously identified chromodomains along with a third N-terminal chromodomain. Chromodomain deletion constructs were used to examine the role of each chromodomain in mediating distinct steps in the LHCP localization mechanism. The C-terminal chromodomain is completely dispensable for LHCP targeting/integration in vitro. The central chromodomain is essential for both targeting complex formation and integration because of its role in binding the M domain of cpSRP54. The N-terminal chromodomain (CD1) is unnecessary for targeting complex formation but is required for integration. This correlates with the ability of CD1 along with the ankyrin repeat region of cpSRP43 to regulate the GTPase cycle of the cpSRP-receptor complex.
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Affiliation(s)
- Robyn L Goforth
- Biological Sciences Department, University of Arkansas, Fayetteville, AK 72701, USA
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47
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Jia L, Dienhart M, Schramp M, McCauley M, Hell K, Stuart RA. Yeast Oxa1 interacts with mitochondrial ribosomes: the importance of the C-terminal region of Oxa1. EMBO J 2004; 22:6438-47. [PMID: 14657017 PMCID: PMC291819 DOI: 10.1093/emboj/cdg624] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The yeast mitochondrial Oxa1 protein is a member of the conserved Oxa1/YidC/Alb3 protein family involved in the membrane insertion of proteins. Oxa1 mediates the insertion of proteins (nuclearly and mitochondrially encoded) into the inner membrane. The mitochondrially encoded substrates interact directly with Oxa1 during their synthesis as nascent chains and in a manner that is supported by the associated ribosome. We have investigated if the Oxa1 complex interacts with the mitochondrial ribosome. Evidence to support a physical association between Oxa1 and the large ribosomal subunit is presented. Our data indicate that the matrix-exposed C-terminal region of Oxa1 plays an important role supporting the ribosomal-Oxa1 interaction. Truncation of this C-terminal segment compromises the ability of Oxa1 to support insertion of substrate proteins into the inner membrane. Oxa1 can be cross-linked to Mrp20, a component of the large ribosomal subunit. Mrp20 is homologous to L23, a subunit located next to the peptide exit tunnel of the ribosome. We propose that the interaction of Oxa1 with the ribosome serves to enhance a coupling of translation and membrane insertion events.
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Affiliation(s)
- Lixia Jia
- Department of Biological Sciences, Marquette University, 530 N. 15th Street, Milwaukee, WI 53233, USA
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48
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Asakura Y, Hirohashi T, Kikuchi S, Belcher S, Osborne E, Yano S, Terashima I, Barkan A, Nakai M. Maize mutants lacking chloroplast FtsY exhibit pleiotropic defects in the biogenesis of thylakoid membranes. THE PLANT CELL 2004; 16:201-14. [PMID: 14688289 PMCID: PMC301405 DOI: 10.1105/tpc.014787] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2003] [Accepted: 11/04/2003] [Indexed: 05/20/2023]
Abstract
A chloroplast signal recognition particle (SRP) that is related to the SRP involved in secretion in bacteria and eukaryotic cells is used for the insertion of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membranes. A conserved component of the SRP mechanism is a membrane-bound SRP receptor, denoted FtsY in bacteria. Plant genomes encode FtsY homologs that are targeted to the chloroplast (cpFtsY). To investigate the in vivo roles of cpFtsY, we characterized maize cpFtsY and maize mutants having a Mu transposon insertion in the corresponding gene (chloroplast SRP receptor1, or csr1). Maize cpFtsY accumulates to much higher levels in leaf tissue than in roots and stems. Interestingly, it is present at similar levels in etiolated and green leaf tissue and was found to bind the prolamellar bodies of etioplasts. A null cpFtsY mutant, csr1-1, showed a substantial loss of leaf chlorophyll, whereas a "leaky" allele, csr1-3, conditioned a more moderate chlorophyll deficiency. Both alleles caused the loss of various LHCPs and the thylakoid-bound photosynthetic enzyme complexes and were seedling lethal. By contrast, levels of the membrane-bound components of the thylakoid protein transport machineries were not altered. The thylakoid membranes in csr1-1 chloroplasts were unstacked and reduced in abundance, but the prolamellar bodies in mutant etioplasts appeared normal. These results demonstrate the essentiality of cpFtsY for the biogenesis not only of the LHCPs but also for the assembly of the other membrane-bound components of the photosynthetic apparatus.
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Affiliation(s)
- Yukari Asakura
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
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Moore M, Goforth RL, Mori H, Henry R. Functional interaction of chloroplast SRP/FtsY with the ALB3 translocase in thylakoids: substrate not required. ACTA ACUST UNITED AC 2003; 162:1245-54. [PMID: 14517205 PMCID: PMC2173952 DOI: 10.1083/jcb.200307067] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Integration of thylakoid proteins by the chloroplast signal recognition particle (cpSRP) posttranslational transport pathway requires the cpSRP, an SRP receptor homologue (cpFtsY), and the membrane protein ALB3. Similarly, Escherichia coli uses an SRP and FtsY to cotranslationally target membrane proteins to the SecYEG translocase, which contains an ALB3 homologue, YidC. In neither system are the interactions between soluble and membrane components well understood. We show that complexes containing cpSRP, cpFtsY, and ALB3 can be precipitated using affinity tags on cpSRP or cpFtsY. Stabilization of this complex with GMP-PNP specifically blocks subsequent integration of substrate (light harvesting chl a/b-binding protein [LHCP]), indicating that the complex occupies functional ALB3 translocation sites. Surprisingly, neither substrate nor cpSRP43, a component of cpSRP, was necessary to form a complex with ALB3. Complexes also contained cpSecY, but its removal did not inhibit ALB3 function. Furthermore, antibody bound to ALB3 prevented ALB3 association with cpSRP and cpFtsY and inhibited LHCP integration suggesting that a complex containing cpSRP, cpFtsY, and ALB3 must form for proper LHCP integration.
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Affiliation(s)
- Misty Moore
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA
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Schünemann D. Structure and function of the chloroplast signal recognition particle. Curr Genet 2003; 44:295-304. [PMID: 14569414 DOI: 10.1007/s00294-003-0450-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2003] [Revised: 09/05/2003] [Accepted: 09/07/2003] [Indexed: 10/26/2022]
Abstract
The targeting of proteins, including the insertion and translocation of proteins in or across membranes, is a fundamental process within a cell, and a variety of specialized mechanisms for protein transport have been developed during evolution. The signal recognition particle (SRP) is found in the cytoplasm of most, if not all, eukaryotes and prokaryotes where it plays a central role in the co-translational insertion of membrane proteins into the endoplasmic reticulum and plasma membrane, respectively. SRP is a ribonucleoprotein consisting of an RNA and at least one polypeptide of approximately 54 kDa (SRP54). Interestingly, chloroplasts contain a specialized type of signal recognition particle. Chloroplast SRP (cpSRP) contains a SRP54 homologue but differs strikingly from cytosolic SRP in various aspects of structure and function. In contrast to cytosolic SRP, it contains a novel protein subunit (cpSRP43) and lacks RNA. CpSRP is also distinctive in its ability to interact with its substrate, light-harvesting chlorophyll a/ b-binding protein, post-translationally. Furthermore, it is remarkable that the 54 kDa subunit of cpSRP is also involved in the co-translational transport of chloroplast-encoded thylakoid proteins, and is therefore able to switch between the co- and post-translational means of interaction with its respective substrate proteins.
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Affiliation(s)
- Danja Schünemann
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, 44780 Bochum, Germany.
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