The Protein Translocon of the Plastid Envelopes

Vojta, Aleksandar; Alavi, Marcel V.; Becker, Thomas; Hörmann, Friederike; Küchler, Michael; Soll, Jürgen; Thomson, Rowena; Schleiff, Enrico

doi:10.1074/jbc.m401968200

Cited by 63 publications

(68 citation statements)

References 21 publications

(30 reference statements)

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“…Instead, it encodes a short N-terminal leader of 30 amino acids upstream of the conserved Tic22 domain, which may function as a transit peptide to the intermembrane space. This is consistent with recent studies that indicate that PsTic22 contains an atypical N-terminal leader that interacts with the outer membrane Toc complex, but does not enter the stroma (Vojta et al 2004). Similarly, the two P. patens Tic22 homologs detected with BlastP searches also lack predicted transit peptides, but have long N-terminal extensions (supplemental Table 6).…”

Section: Resultssupporting

confidence: 79%

The Chloroplast Protein Translocation Complexes ofChlamydomonas reinhardtii: A Bioinformatic Comparison of Toc and Tic Components in Plants, Green Algae and Red Algae

2008

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The recently completed genome of Chlamydomonas reinhardtii was surveyed for components of the chloroplast protein translocation complexes. Putative components were identified using reciprocal BlastP searches with the protein sequences of Arabidopsis thaliana as queries. As a comparison, we also surveyed the new genomes of the bryophyte Physcomitrella patens, two prasinophyte green algae (Ostreococcus lucimarinus and Ostreococcus tauri), the red alga Cyanidioschizon merolae, and several cyanobacteria. Overall, we found that the components of the import pathway are remarkably well conserved, particularly among the Viridiplantae lineages. Specifically, C. reinhardtii contained almost all the components found in A. thaliana, with two exceptions. Missing from C. reinhardtii are the C-terminal ferredoxin-NADPH-reductase (FNR) binding domain of Tic62 and a full-length, TPR-bearing Toc64. Further, the N-terminal domain of C. reinhardtii Toc34 is highly acidic, whereas the analogous region in C. reinhardtii Toc159 is not. This reversal of the vascular plant model may explain the similarity of C. reinhardtii chloroplast transit peptides to mitochondrial-targeting peptides. Other findings from our genome survey include the absence of Tic22 in both Ostreococcus genomes; the presence of only one Toc75 homolog in C. merolae; and, finally, a distinctive propensity for gene duplication in P. patens.

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Section: Resultssupporting

confidence: 79%

The Chloroplast Protein Translocation Complexes ofChlamydomonas reinhardtii: A Bioinformatic Comparison of Toc and Tic Components in Plants, Green Algae and Red Algae

2008

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“…Nevertheless, these data are not sufficient to prove a cytoplasmic localization ñor do they exelude AMI1 from organdíes, which could have been disrupted during the preparation procedure, thus releasing their soluble proteins. Some recent publications (Vojta et al 2004;Chew et al 2004) assumed a possible plastidial or mitochondrial localization of AMI1, associating AMI1 with two proteins, Toc64-III and mtOM64, mainly based on their primary amino acid sequence homology, emphasized by the clustering of the three proteins into one branch of a phylogenetic tree (Fig. Ib).…”

Section: Subcellular Localization Of Ami1mentioning

confidence: 99%

Subcellular localization and tissue specific expression of amidase 1 from Arabidopsis thaliana

Pollmann

Neu

Lehmann

et al. 2006

Planta

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Amidase 1 (AMIl) from Arabidopsis thaliana converts indole-3-acetamide (IAM), into indole-3-acetic acid (IAA). AMIl is part of a small isogene family comprising seven members in A. thaliana encoding proteins which share a conserved glycine-and serinerich amidase-signature. One member of this family has been characterized as an iV-acylethanolamine-cleaving fatty acid amidohydrolase (FAAH) and two other members are part of the preprotein translocon of the outer envelope of chloroplasts (Toe complex) or mitochondria (Tom complex) and presumably lack enzymatic activity. Among the hitherto characterized proteins of this family, AMIl is the only member with indole-3-acetamide hydrolase activity, and IAM is the preferred substrate while iV-acylethanolamines and oleamide are not hydrolyzed significantly, thus suggesting a role of AMIl in auxin biosynthesis. Whereas the enzymatic function of AMIl has been determined in vitro, the subcellular localization of the enzyme remained unclear. By using different GFP-fusion construets and an A. thaliana transient expression system,

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“…On the other hand, Tic110 features make it a good candidate for a translocation channel: it is conserved in different plastid types from multiple plant species [11]; it is expressed in cells in comparable amounts to Toc75 [97]; it shows channel activity in vitro [81]; it is found associated with precursor proteins and chaperones [77,86]; it forms supercomplexes with the TOC complex [98]; and it is essential for plant development [76]. In any case, Tic110 has an essential role in preprotein recognition on the trans side where it associates with Tic40 which links the central translocation channel to the import motor [99].…”

Section: Models Of Protein Import Through the Toc Complexmentioning

confidence: 99%

Protein import machineries in endosymbiotic organelles

Balsera

Soll

Bölter

2009

Cell. Mol. Life Sci.

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Abstract. Chloroplast and mitochondria, the two organelles with an accepted endosymbiotic origin, have developed multiple translocation pathways to ensure the subcellular allocation of proteins synthesized by cytosolic ribosomes, and to guarantee their assembly into functional complexes in coordination also with organellar-encoded subunits. The evolution of different protein import machineries was thus essential for the development of these two organelles within cells. A general overview of the translocation machineries in chloroplast and mitochondrial membranes involved in targeting and import of nuclearencoded proteins, with special focus on plant cells where the two organelles coexist, is expounded.Keywords. Protein translocation, mitochondria, chloroplasts, thylakoids, dual-targeting, endosymbiotic organelles. Endosymbiosis and the plant cellIt is widely accepted that mitochondria, found in eukaryotic cells, and plastids, just in plant cells, are organelles of endosymbiotic origin [1]. Two independent endosymbiotic events gave rise to the evolution of these organelles in a plant cell. First, mitochondria evolved from a single endosymbiotic event between a host cell and an aerobic a-proteobacterium. As a consequence, a diversity of heterotrophic eukaryotic lineages emerged [2]. Later, plastids were incorporated from a free-living photosynthetic prokaryote, an ancestor of contemporary cyanobacteria, which was engulfed by a heterotrophic eukaryotic host that already contained mitochondria. The primary endosymbiotic event in plastid evolution gave rise to glaucophyta, rhodophyta and viridiplantae lineages [3]. Subsequent endosymbiotic events in plastid evolution have occurred [4]. With time, the majority of the genetic information from the endosymbionts was lost or transferred to the nucleus of the host cell, though some amount of information is still retained by the organelles, thus functioning as a semiautonomous system [5]. Because of the gene relocation in the host cell, several mechanisms were developed to re-target and efficiently transport the proteins acting in the organelles but now expressed in the host cytosol. Some of these machineries were adapted from bacteria; others show

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The Protein Translocon of the Plastid Envelopes

Cited by 63 publications

References 21 publications

The Chloroplast Protein Translocation Complexes ofChlamydomonas reinhardtii: A Bioinformatic Comparison of Toc and Tic Components in Plants, Green Algae and Red Algae

The Chloroplast Protein Translocation Complexes ofChlamydomonas reinhardtii: A Bioinformatic Comparison of Toc and Tic Components in Plants, Green Algae and Red Algae

Subcellular localization and tissue specific expression of amidase 1 from Arabidopsis thaliana

Protein import machineries in endosymbiotic organelles

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