The physical and functional borders of transit peptide-like sequences in secondary endosymbionts

Felsner, Gregor; Sommer, Maik S.; Maier, Uwe G.

doi:10.1186/1471-2229-10-223

Cited by 20 publications

(20 citation statements)

References 42 publications

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“…Diatom TPs may not need to be as long as plant TPs because they are hidden until the SP is cleaved off after the protein is already partly inserted into the ER, avoiding the danger of misdirection to the mitochondrion. The previously reported net positive charge, which was confirmed for almost all TPs identified in our study, is thought to be required for transit across the plastid envelope, but not for traversing the periplastidal membrane [36]. The TPs were enriched in hydroxylated amino acids that may play a role in keeping the precursor in an import competent state in the periplasm, possibly by interaction with resident chaperones [37,38].…”

Section: Discussionsupporting

confidence: 83%

Proteomic Amino-Termini Profiling Reveals Targeting Information for Protein Import into Complex Plastids

et al. 2013

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In organisms with complex plastids acquired by secondary endosymbiosis from a photosynthetic eukaryote, the majority of plastid proteins are nuclear-encoded, translated on cytoplasmic ribosomes, and guided across four membranes by a bipartite targeting sequence. In-depth understanding of this vital import process has been impeded by a lack of information about the transit peptide part of this sequence, which mediates transport across the inner three membranes. We determined the mature N-termini of hundreds of proteins from the model diatom Thalassiosira pseudonana, revealing extensive N-terminal modification by acetylation and proteolytic processing in both cytosol and plastid. We identified 63 mature N-termini of nucleus-encoded plastid proteins, deduced their complete transit peptide sequences, determined a consensus motif for their cleavage by the stromal processing peptidase, and found evidence for subsequent processing by a plastid methionine aminopeptidase. The cleavage motif differs from that of higher plants, but is shared with other eukaryotes with complex plastids.

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Section: Discussionsupporting

confidence: 83%

Proteomic Amino-Termini Profiling Reveals Targeting Information for Protein Import into Complex Plastids

et al. 2013

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“…Earlier studies have revealed that the presence of a GFP reporter directly adjacent to potential trafficking motifs may either inhibit or be conducive to protein transport2021. We wished to investigate whether the GFP reporter itself may be acting as a spacer which may either increase or decrease export efficiency.…”

Section: Resultsmentioning

confidence: 99%

Trafficking of the exported P. falciparum chaperone PfHsp70x

Rhiel

Bittl

Tribensky

et al. 2016

Sci Rep

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Plasmodium falciparum extensively modifies its chosen host cell, the mature human erythrocyte. This remodelling is carried out by parasite-encoded proteins that are exported into the host cell. To gain access to the human red blood cell, these proteins must cross the parasitophorous vacuole, a membrane bound compartment surrounding the parasite that is generated during the invasion process. Many exported proteins carry a so-called PEXEL/HT signal that directs their transport. We recently reported the unexpected finding of a species-restricted parasite-encoded Hsp70, termed PfHsp70x, which is exported into the host erythrocyte cytosol. PfHsp70x lacks a classical PEXEL/HT motif, and its transport appears to be mediated by a 7 amino acid motif directly following the hydrophobic N-terminal secretory signal. In this report, we analyse this short targeting sequence in detail. Surprisingly, both a reversed and scrambled version of the motif retained the capacity to confer protein export. Site directed mutagenesis of glutamate residues within this region leads to a block of protein trafficking within the lumen of the PV. In contrast to PEXEL-containing proteins, the targeting signal is not cleaved, but appears to be acetylated. Furthermore we show that, like other exported proteins, trafficking of PfHsp70x requires the vacuolar translocon, PTEX.

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“…However, in diatoms intermediates that are transported across only one or two of the four plastid membranes can be discriminated from those imported across all four, and studies in the model system Phaeodactylum tricornutum revealed a complex set of signals [43]. It was shown that the positive net charge of the TP is important to cross the two innermost membranes, and required to cross the second outermost membrane into the PPC [44]. Negative charges in the TP were shown to inhibit entry into the PPC of diatoms [44], but in contrast are required for PPC targeting in chlorarachniophytes [45].…”

Section: Signals For Organellar Targetingmentioning

confidence: 99%

“…It was shown that the positive net charge of the TP is important to cross the two innermost membranes, and required to cross the second outermost membrane into the PPC [44]. Negative charges in the TP were shown to inhibit entry into the PPC of diatoms [44], but in contrast are required for PPC targeting in chlorarachniophytes [45]. This may represent a fundamental difference in these pathways originating from different algal lineages.…”

Section: Signals For Organellar Targetingmentioning

confidence: 99%

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Protein sorting in complex plastids

Sheiner

Striepen

2013

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

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Taming a cyanobacterium in a pivitol event of endosymbiosis brought photosynthesis to eukaryotes, and gave rise to the plastids found in glaucophytes, red and green algae, and the descendants of the latter, the plants. Ultrastructural as well as molecular research over the last two decades has demonstrated that plastids have enjoyed surprising lateral mobility across the tree of life. Numerous independent secondary and tertiary endosymbiosis have led to a spread of plastids into a variety of, up to that point, non-photosynthetic lineages. Happily eating and subsequently domesticating one another protists conquered a wide variety of ecological niches. The elaborate evolution of secondary, or complex, plastids is reflected in the numerous membranes that bound them (three or four compared to the two membranes of the primary plastids). Gene transfer to the host nucleus is a hallmark of endosymbiosis and provides centralized cellular control. Here we review how these proteins find their way back into the stroma of the organelle and describe the advances in the understanding of the molecular mechanisms that allow protein translocation across four membranes.

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The physical and functional borders of transit peptide-like sequences in secondary endosymbionts

Cited by 20 publications

References 42 publications

Proteomic Amino-Termini Profiling Reveals Targeting Information for Protein Import into Complex Plastids

Proteomic Amino-Termini Profiling Reveals Targeting Information for Protein Import into Complex Plastids

Trafficking of the exported P. falciparum chaperone PfHsp70x

Protein sorting in complex plastids

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