Toc64 - A Preprotein-receptor at the Outer Membrane with Bipartide Function

Qbadou, Soumya; Becker, Thomas; Bionda, Tihana; Reger, Katharina; Ruprecht, Maike; Soll, Jürgen; Schleiff, Enrico

doi:10.1016/j.jmb.2007.01.047

Cited by 81 publications

(82 citation statements)

References 49 publications

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“…In other cases, the Hsp70 and type III J-domain protein are recruited independently to the site of action, where the J-domain protein stimulates ATP hydrolysis by the partner Hsp70. This can be observed for the import machinery of mitochondria and chloroplasts (Westermann and Neupert, 1997;Becker et al, 2004;Kozany et al, 2004;Qbadou et al, 2007). The divergence of the C terminus among the type III J-domain proteins and their uniqueness suggests the possibility that they bind very different proteins.…”

Section: Discussionmentioning

confidence: 93%

OWL1: An Arabidopsis J-Domain Protein Involved in Perception of Very Low Light Fluences

Kneissl¹,

Wachtler

Chua

et al. 2009

Plant Cell

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Section: Discussionmentioning

confidence: 93%

OWL1: An Arabidopsis J-Domain Protein Involved in Perception of Very Low Light Fluences

Kneissl¹,

Wachtler

Chua

et al. 2009

Plant Cell

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“…genomes contain a full-length Toc64 ortholog, including the TPR domain (Table 1). However, the prasinophyte orthologs retain a serine residue in the catalytic triad of the amidase, which distinguishes them from the vascular plant Toc64 proteins (Figure 9) (Sohrt and Soll 2000;Qbadou et al 2007). Similarly, the three full-length Toc64 orthologs detected in P. patens (Table 1) contain the catalytic serine residue within their amidase domains (Figure 9).…”

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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“…Thus, the role of the cytosolic domain of METAXIN remains unclear in other organisms; however, its ability to interact with a variety of precursor proteins suggests it may play another role in addition to the assembly of b-barrel proteins and thus interact with proteins on both the outside and inside of the outer membrane. Notably, At TOC64-III in chloroplasts has been proposed to play a role in precursor binding on the cytosolic and inter envelope space (Qbadou et al, 2007).…”

Section: A Multifunctional Metaxin?mentioning

confidence: 99%

Functional Definition of Outer Membrane Proteins Involved in Preprotein Import into Mitochondria

et al. 2007

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The role of plant mitochondrial outer membrane proteins in the process of preprotein import was investigated, as some of the principal components characterized in yeast have been shown to be absent or evolutionarily distinct in plants. Three outer membrane proteins of Arabidopsis thaliana mitochondria were studied: TOM20 (translocase of the outer mitochondrial membrane), METAXIN, and mtOM64 (outer mitochondrial membrane protein of 64 kD). A single functional Arabidopsis TOM20 gene is sufficient to produce a normal multisubunit translocase of the outer membrane complex. Simultaneous inactivation of two of the three TOM20 genes changed the rate of import for some precursor proteins, revealing limited isoform subfunctionalization. Inactivation of all three TOM20 genes resulted in severely reduced rates of import for some but not all precursor proteins. The outer membrane protein METAXIN was characterized to play a role in the import of mitochondrial precursor proteins and likely plays a role in the assembly of β-barrel proteins into the outer membrane. An outer mitochondrial membrane protein of 64 kD (mtOM64) with high sequence similarity to a chloroplast import receptor was shown to interact with a variety of precursor proteins. All three proteins have domains exposed to the cytosol and interacted with a variety of precursor proteins, as determined by pull-down and yeast two-hybrid interaction assays. Furthermore, inactivation of one resulted in protein abundance changes in the others, suggesting functional redundancy. Thus, it is proposed that all three components directly interact with precursor proteins to participate in early stages of mitochondrial protein import.

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Toc64 - A Preprotein-receptor at the Outer Membrane with Bipartide Function

Cited by 81 publications

References 49 publications

OWL1: An Arabidopsis J-Domain Protein Involved in Perception of Very Low Light Fluences

OWL1: An Arabidopsis J-Domain Protein Involved in Perception of Very Low Light Fluences

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

Functional Definition of Outer Membrane Proteins Involved in Preprotein Import into Mitochondria

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