Arabidopsis Tic110 Is Essential for the Assembly and Function of the Protein Import Machinery of Plastids

Inaba, Tomoki; Alvarez-Huerta, Mayte; Li, Ming; Bauer, Jörg; Ewers, Carolin; Kessler, Félix; Schnell, Danny J.

doi:10.1105/tpc.105.030700

Cited by 131 publications

(170 citation statements)

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“…Tic110 and Tic40 have been proposed to have roles in the recruitment of stromal molecular chaperones to the stromal face of TIC 2,6,11 . The tic110 and tic40 mutant plants also showed dramatically reduced levels of LHCP, and had few granal stacks 8,42,43 . Thus, LTD may be specifically recruited to the envelope for pLHCP full-length His-tagged LTD was used as the prey, and GsT, full-length GsT-tagged Tic40, and C-terminal parts of Tic110 stromal domain (amino acids 385-1,016) were used as bait, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The protein import complexes located on the outer and inner envelope membranes are termed as TOC (translocon at the outer envelop membrane of chloroplast) and TIC (translocon at the inner envelop membrane of chloroplast) complexes, respectively 1,2,5,6 . The Toc159, Toc75 and Toc34 proteins form the core TOC complex and are involved in protein transport across the outer envelope [6][7][8] . Tic110, Tic20 and Tic21 have been suggested to function as the protein translocation channel of the inner envelope 1,2,7,8 .…”

mentioning

confidence: 99%

“…The Toc159, Toc75 and Toc34 proteins form the core TOC complex and are involved in protein transport across the outer envelope [6][7][8] . Tic110, Tic20 and Tic21 have been suggested to function as the protein translocation channel of the inner envelope 1,2,7,8 . Several stromal proteins, including chaperones, proteases and redox regulators, are also involved in the import process 6,9,10 .…”

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LTD is a protein required for sorting light-harvesting chlorophyll-binding proteins to the chloroplast SRP pathway

Ouyang

et al. 2011

Nat Commun

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Higher plants require chloroplasts for essential functions in photosynthesis and other important physiological processes, such as sugar, lipid and amino-acid biosynthesis. most chloroplast proteins are nuclear-encoded proteins that are synthesized in the cytosol as precursors, and imported into chloroplasts by protein translocases in the outer and inner chloroplast envelope. The imported chloroplast proteins are then translocated into or across the thylakoid membrane by four distinct pathways. However, the mechanisms by which the imported nuclear-encoded proteins are delivered to these pathways remain largely unknown. Here we show that an Arabidopsis ankyrin protein, LTD (mutation of which causes the light-harvesting chlorophyllbinding protein translocation defect), is localized in the chloroplast and using yeast two-hybrid screens demonstrate that LTD interacts with both proteins from the signal recognition particle (sRP) pathway and the inner chloroplast envelope. our study shows that LTD is essential for the import of light-harvesting chlorophyll-binding proteins and subsequent routing of these proteins to the chloroplast sRP-dependent pathway.

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Section: Discussionmentioning

confidence: 99%

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LTD is a protein required for sorting light-harvesting chlorophyll-binding proteins to the chloroplast SRP pathway

Ouyang

et al. 2011

Nat Commun

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“…These functionally-distinct import routes seem to converge at the TIC complex via atTic110 (Ivanova et al , 2004 ). However, the differential expression of Tic20 may suggest that they represent alternative TIC translocation complexes that contribute to the distinct targeting pathways together with the different TOC core complex (Inaba et al , 2005 ;see below). Multiple structural and functionally-distinct TOC core complexes have thus far been reported in Arabidopsis .…”

Section: Multiple Import Pathwaysmentioning

confidence: 99%

“…In this context, multiple import pathways allow efficient targeting of ' housekeeping ' vs. highly expressed proteins (which are required for specialized metabolic functions) in the dynamic nature of plastids (Inaba et al , 2005 ).…”

Section: Multiple Import Pathwaysmentioning

confidence: 99%

The gateway to chloroplast: re-defining the function of chloroplast receptor proteins

Chang¹,

Soll²,

Bölter³

2012

Biological Chemistry

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: Chloroplast biogenesis often requires a tight orchestration between gene expression (both plastidial and nuclear) and translocation of ~ 3000 nuclear-encoded proteins into the organelle. Protein translocation is achieved via two multimeric import machineries at the outer (TOC) and inner (TIC) envelope of chloroplast, respectively. Three components constitute the core element of the TOC complex: a β -barrel protein translocation channel Toc75 and two receptor constituents, Toc159 and Toc34. A diverse set of distinct TOC complexes have recently been characterized and these diversified TOC complexes have evolved to coordinate the translocation of differentially expressed proteins. This review aims to describe the recent discoveries relating to the typical characteristics of these distinct TOC complexes, particularly the receptor constituents, which are the main contributors for TOC complex diversification.

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Protein Translocation across Membranes

Perry

2010

Encyclopedia of Life Sciences

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Cells are divided into compartments that serve to separate and coordinate metabolic processes. In eukaryotic cells, almost all enzymes, along with proteins involved in their maintenance, are encoded by genes in the nucleus. Proteins are translated in the cytoplasm, and must be targeted to the correct compartment within the cell in order to faithfully carry out their function. To achieve this, proteins are synthesized with signal sequences that guide them to receptor proteins that in turn transfer them to large transmembrane protein channels of organelles. The molecular machinery for protein translocation has evolved to capture and recognize proteins with the correct targeting signals encoded in their amino acid sequence. These diverse classes of translocases pass substrate proteins across, or into, membranes cotranslationally or posttranslationally. Protein substrates are moved by active pushing, pulling, electrophoretic and Brownian ratchet mechanisms. Most translocases operate on unfolded polypeptides, whereas some can transport partially or fully folded proteins. Key Concepts: Cells contain sophisticated molecular machines to recognize and translocate proteins across membranes and into their correct organelles. Proteins are targeted to subcellular locations via targeting signals encoded in their amino acid sequence. These usually exist as linear sequences in the N ‐ or C ‐terminal region of the protein; however, some targeting signals occur within internal segments of the substrate polypeptide. Not all targeting signals are well defined. Receptors associated with the translocase and in the cytosol specifically recognize targeting signals. Translocases contain pores through which the substrate proteins can pass. Most translocase pores are only large enough to accommodate unfolded proteins, although some appear to be able to accommodate fully folded polypeptides. Molecular chaperones maintain substrates in an unfolded state before translocation and assist their correct folding after translocation. The force required to translocate proteins across membranes can come from several sources; the electrophoretic potential or pH gradient across the membrane, an ATP‐ or GTP‐driven pushing or pulling mechanism and an ATP‐driven Brownian ratchet mechanism.

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Arabidopsis Tic110 Is Essential for the Assembly and Function of the Protein Import Machinery of Plastids

Cited by 131 publications

References 30 publications

LTD is a protein required for sorting light-harvesting chlorophyll-binding proteins to the chloroplast SRP pathway

LTD is a protein required for sorting light-harvesting chlorophyll-binding proteins to the chloroplast SRP pathway

The gateway to chloroplast: re-defining the function of chloroplast receptor proteins

Protein Translocation across Membranes

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