Organelle import of proteins with dual targeting properties into mitochondria and chloroplasts takes place by the general import pathways

Langner, Uwe; Baudisch, Bianca; Klösgen, Ralf Bernd

doi:10.4161/psb.29301

Cited by 12 publications

(11 citation statements)

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“…MU-LOC was developed to predict mitochondrial proteins in plant cells, where one of the challenges is that hundreds of proteins are dually targeted to mitochondria and plastids [ 30 , 31 ]. The protein features used to discriminate (see above) are actually species/kingdom neutral, so MU-LOC should also be able to predict mitochondrial localization in animal cells.…”

Section: Mitochondrial Transporters—predictionsmentioning

confidence: 99%

Proteomic and Bioinformatic Profiling of Transporters in Higher Plant Mitochondria

et al. 2020

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To function as a metabolic hub, plant mitochondria have to exchange a wide variety of metabolic intermediates as well as inorganic ions with the cytosol. As identified by proteomic profiling or as predicted by MU-LOC, a newly developed bioinformatics tool, Arabidopsis thaliana mitochondria contain 128 or 143 different transporters, respectively. The largest group is the mitochondrial carrier family, which consists of symporters and antiporters catalyzing secondary active transport of organic acids, amino acids, and nucleotides across the inner mitochondrial membrane. An impressive 97% (58 out of 60) of all the known mitochondrial carrier family members in Arabidopsis have been experimentally identified in isolated mitochondria. In addition to many other secondary transporters, Arabidopsis mitochondria contain the ATP synthase transporters, the mitochondria protein translocase complexes (responsible for protein uptake across the outer and inner membrane), ATP-binding cassette (ABC) transporters, and a number of transporters and channels responsible for allowing water and inorganic ions to move across the inner membrane driven by their transmembrane electrochemical gradient. A few mitochondrial transporters are tissue-specific, development-specific, or stress-response specific, but this is a relatively unexplored area in proteomics that merits much more attention.

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Section: Mitochondrial Transporters—predictionsmentioning

confidence: 99%

Proteomic and Bioinformatic Profiling of Transporters in Higher Plant Mitochondria

et al. 2020

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“…These proteins harbor an ambiguous targeting signal (Small et al, 1998 ; Silva-Filho, 2003 ; Yogev and Pines, 2011 ) that induces the concomitant transport to alternative destinations by overlapping targeting signals (Figure 4C ). Such targeting signals have been predominantly found in plant proteins bilocalized to mitochondria and chloroplasts (Carrie and Small, 2013 ; Baudisch et al, 2014 ) and use the traditional import pathways into these organelles (Langner et al, 2014 ). The amino acid composition of N-terminal sequences encoding ambiguous targeting signals show properties of both targeting signals, which emphasizes the intermediate state of such peptides (Pujol et al, 2007 ).…”

Section: Dual Targeting and Bilocalization Of Proteinsmentioning

confidence: 99%

The similarity between N-terminal targeting signals for protein import into different organelles and its evolutionary relevance

2015

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The proper distribution of proteins between the cytosol and various membrane-bound compartments is crucial for the functionality of eukaryotic cells. This requires the cooperation between protein transport machineries that translocate diverse proteins from the cytosol into these compartments and targeting signal(s) encoded within the primary sequence of these proteins that define their cellular destination. The mechanisms exerting protein translocation differ remarkably between the compartments, but the predominant targeting signals for mitochondria, chloroplasts and the ER share the N-terminal position, an α-helical structural element and the removal from the core protein by intraorganellar cleavage. Interestingly, similar properties have been described for the peroxisomal targeting signal type 2 mediating the import of a fraction of soluble peroxisomal proteins, whereas other peroxisomal matrix proteins encode the type 1 targeting signal residing at the extreme C-terminus. The structural similarity of N-terminal targeting signals poses a challenge to the specificity of protein transport, but allows the generation of ambiguous targeting signals that mediate dual targeting of proteins into different compartments. Dual targeting might represent an advantage for adaptation processes that involve a redistribution of proteins, because it circumvents the hierarchy of targeting signals. Thus, the co-existence of two equally functional import pathways into peroxisomes might reflect a balance between evolutionary constant and flexible transport routes.

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“…One way to distinguish between chloroplast and mitochondrial import of a candidate protein are competition experiments in which saturating amounts of an unlabelled precursor protein with known organelle targeting specificity are added together with the radiolabelled candidate protein to the in organello assays (Rödiger et al, 2011; Baudisch and Klösgen, 2012; Langner et al, 2014). Here we have used the precursor of the mitochondrial Rieske protein as competitor, which was obtained by heterologous overexpression in E. coli and subsequent purification.…”

Section: Resultsmentioning

confidence: 99%

“…Incubation with intact mitochondria or chloroplasts isolated from pea leaves was performed as described in Rödiger et al (2010) with the exception that the transport assays were additionally supplemented with 2 mM NADH. Competition experiments were performed as described (Molik et al, 2001; Langner et al, 2014).…”

Section: Methodsmentioning

confidence: 99%

Dual targeting of TatA points to a chloroplast-like Tat pathway in plant mitochondria

Bennewitz

Sharma

Tannert

et al. 2020

Preprint

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The biogenesis of membrane-bound electron transport chains requires membrane translocation pathways for folded proteins carrying complex cofactors, like the Rieske Fe/S proteins. Two independent systems were developed during evolution, namely the Twinarginine translocation (Tat) pathway, which is present in bacteria and chloroplasts, and the Bcs1 pathway found in mitochondria of yeast and mammals. Mitochondria of plants carry a Tat-like pathway which was hypothesized to operate with only two subunits, a TatB-like protein and a TatC homolog (OrfX), but lacking TatA. Here we show that the nuclearly encoded TatA has dual targeting properties, i.e., it can be imported into both, chloroplasts and mitochondria. Dual targeting of TatA was observed with in organello experiments employing isolated chloroplasts and mitochondria as well as after transient expression of suitable reporter constructs in epidermal leaf cells. The extent of transport of these constructs into mitochondria of transiently transformed leaf cells was relatively low, causing a demand for highly sensitive methods to be detected, like the sasplitGFP approach. Yet, the dual import of TatA into mitochondria and chloroplasts observed here points to a common mechanism of Tat transport for folded proteins within both endosymbiotic organelles.

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Organelle import of proteins with dual targeting properties into mitochondria and chloroplasts takes place by the general import pathways

Cited by 12 publications

References 12 publications

Proteomic and Bioinformatic Profiling of Transporters in Higher Plant Mitochondria

Proteomic and Bioinformatic Profiling of Transporters in Higher Plant Mitochondria

The similarity between N-terminal targeting signals for protein import into different organelles and its evolutionary relevance

Dual targeting of TatA points to a chloroplast-like Tat pathway in plant mitochondria

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