Characterization of the protein import apparatus in isolated outer envelopes of chloroplasts

Waegemann, Karin; Soil, Jürgen

doi:10.1111/j.1365-313x.1991.00149.x

Cited by 176 publications

(79 citation statements)

References 35 publications

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“…Together with Toc75, both Toc34 and Toc159 constitute the core components of the Toc complex due to their stable interactions with each other and the transit peptide (Waegemann and Soll 1991). Unlike Toc75, neither GTPase protein has a cyanobacterial ortholog, indicating a eukaryotic origin for these receptor components (Reumann et al 2005).…”

Section: Resultsmentioning

confidence: 99%

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: Resultsmentioning

confidence: 99%

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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“…Low-molecularweight substances (< 10000 Da) can pass rather freely via porin-like proteins through the outer envelope (Flfigge and Benz 1984). Larger molecules such as precursor proteins destined for the inside of the organelle are recognized on the surface (cytosolic leaflet) of the outer envelope by specific receptors and translocated inside the plastid by a multiprotein complex (Waegemann and Soll 1991). Precursor-protein binding capacity is proteasesensitive not only in chloroplasts but also in isolated outer envelopes and membranes obtained from either top or bottom phase of the aqueous two-phase polymer system.…”

Section: Discussionmentioning

confidence: 99%

Outer envelope membranes from chloroplasts are isolated as right-side-out vesicles

Waegemann

Eichacker

Soll

1992

Planta

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Abstract. Outer envelope membranes were isolated from purified chloroplasts of pea leaves. The sidedness of the vesicles was analyzed by (i) aqueous polymer-two phase partitioning, (ii) the effect of limited proteolysis on the outer-envelope proteins (OEP) 86 and OEP 7 in intact organelles and isolated membranes, (iii) fluorescencemicroscopy and finally (iv) binding of precursor polypeptides to isolated outer-membrane vesicles. The results demonstrate that purified outer envelope membranes occur largely (> 90%) as right-side-out vesicles.

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“…Although it is not clear where the ATP-utilizing component may reside, previous studies have shown that a stable association of preproteins with the translocon components, the so-called early import intermediate, was generated under low ATP concentrations (Waegemann and Soll, 1991;Perry and Keegstra, 1994;Schnell et al, 1994;Ma et al, 1996;Akita et al, 1997;Kouranov and Schnell, 1997;Nielsen et al, 1997;Young et al, 1999;Inoue and Akita, 2008). In the presence of higher concentrations of ATP (>1 mM), complete translocation of preproteins across the double envelope of chloroplasts occurs.…”

Section: Introductionmentioning

confidence: 95%

A 1-Megadalton Translocation Complex Containing Tic20 and Tic21 Mediates Chloroplast Protein Import at the Inner Envelope Membrane

et al. 2009

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Chloroplast protein import is mediated by two hetero-oligomeric protein complexes, the Tic and Toc translocons, which are located in the inner and outer envelope membranes. At the inner membrane, many Tic components have been identified and characterized, but it remains unclear how these Tic proteins are organized to form a protein-conducting channel or whether a stable Tic core complex that binds translocating preproteins exists. Here, we report the identification of a 1-megadalton (MD) translocation complex as an intermediate during protein translocation across the inner membrane in Arabidopsis thaliana and pea (Pisum sativum). This complex can be detected by blue native PAGE using the mild detergent digitonin without any chemical cross-linkers. The preprotein arrested in the 1-MD complex can be chased into its fully translocated form after a subsequent incubation. While Tic20 and Tic21 appear to be involved in the 1-MD complex, Tic110, a wellcharacterized Tic component, exists as a distinct entity from the complex. Several lines of evidence suggest that the 1-MD complex functions in between the Toc and Tic110-containing complexes, most likely as a protein-conducting channel at the inner envelope.

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Characterization of the protein import apparatus in isolated outer envelopes of chloroplasts

Cited by 176 publications

References 35 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

Outer envelope membranes from chloroplasts are isolated as right-side-out vesicles

A 1-Megadalton Translocation Complex Containing Tic20 and Tic21 Mediates Chloroplast Protein Import at the Inner Envelope Membrane

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