Protein import into chloroplasts: new aspects of a well-known topic

Stengel, Anna; Soll, Jürgen; Bölter, Bettina

doi:10.1515/bc.2007.099

Cited by 37 publications

(39 citation statements)

References 49 publications

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“…The rationale behind this proposed function is the presence in TIC55 of redox-active cysteine residues at the C terminus that have been shown to be regulated by the thioredoxin system (Bartsch et al, 2008). Furthermore, the other two components of the so-called redox regulon (Stengel et al, 2007), i.e., TIC62 and TIC32, possess NADPH binding sites and could exert their regulatory role depending on changes of the NADP + /NADPH ratio, a well known readout of the redox state of the chloroplast. Indeed, TIC62 was shown to shuttle between thylakoids and the inner envelope in a NADP + /NADPH ratio-dependent manner (Stengel et al, 2008), which together with its additional ability to bind FNR ) could allow electron fluxes at these membranes to be highly dynamically regulated (Bölter et al, 2015).…”

Section: Discussion Phyllobilin Hydroxylation By Tic55mentioning

confidence: 99%

A Role for TIC55 as a Hydroxylase of Phyllobilins, the Products of Chlorophyll Breakdown during Plant Senescence

et al. 2016

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ORCID IDs: 0000-0002-0044-0490 (M.H.); 0000-0002-7598-3609 (S.A.) Chlorophyll degradation is the most obvious hallmark of leaf senescence. Phyllobilins, linear tetrapyrroles that are derived from opening of the chlorin macrocycle by the Rieske-type oxygenase PHEOPHORBIDE a OXYGENASE (PAO), are the end products of chlorophyll degradation. Phyllobilins carry defined modifications at several peripheral positions within the tetrapyrrole backbone. While most of these modifications are species-specific, hydroxylation at the C3 2 position is commonly found in all species analyzed to date. We demonstrate that this hydroxylation occurs in senescent chloroplasts of Arabidopsis thaliana. Using bell pepper (Capsicum annuum) chromoplasts, we establish that phyllobilin hydroxylation is catalyzed by a membrane-bound, molecular oxygen-dependent, and ferredoxin-dependent activity. As these features resemble the requirements of PAO, we considered membrane-bound Rieske-type oxygenases as potential candidates. Analysis of mutants of the two Arabidopsis Rieske-type oxygenases (besides PAO) uncovered that phyllobilin hydroxylation depends on TRANSLOCON AT THE INNER CHLOROPLAST ENVELOPE55 (TIC55). Our work demonstrates a catalytic activity for TIC55, which in the past has been considered as a redox sensor of protein import into plastids. Given the wide evolutionary distribution of both PAO and TIC55, we consider that chlorophyll degradation likely coevolved with land plants.

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Section: Discussion Phyllobilin Hydroxylation By Tic55mentioning

confidence: 99%

A Role for TIC55 as a Hydroxylase of Phyllobilins, the Products of Chlorophyll Breakdown during Plant Senescence

et al. 2016

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“…1) usually required for insertion into the plastid envelope (53). However, in recent years multiple examples of chloroplast envelope-located membrane proteins lacking N-terminallocated transit peptides have been reported (54), and about FIGURE 7. Histochemical localization of GUS expression under control of the Atndt1 and Atndt2 promoter in A. thaliana.…”

Section: Discussionmentioning

confidence: 99%

Molecular Identification and Functional Characterization of Arabidopsis thaliana Mitochondrial and Chloroplastic NAD+ Carrier Proteins

Palmieri

Rieder

Ventrella

et al. 2009

Journal of Biological Chemistry

157

172

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The Arabidopsis thaliana L. genome contains 58 membrane proteins belonging to the mitochondrial carrier family. Two mitochondrial carrier family members, here named AtNDT1 and AtNDT2, exhibit high structural similarities to the mitochondrial nicotinamide adenine dinucleotide (NAD ؉ ) carrierScNDT1 from bakers' yeast. Expression of AtNDT1 or AtNDT2 restores mitochondrial NAD ؉ transport activity in a yeast mutant lacking ScNDT. Localization studies with green fluorescent protein fusion proteins provided evidence that AtNDT1 resides in chloroplasts, whereas only AtNDT2 locates to mitochondria. Heterologous expression in Escherichia coli followed by purification, reconstitution in proteoliposomes, and uptake experiments revealed that both carriers exhibit a submillimolar affinity for NAD ؉ and transport this compound in a counterexchange mode. Among various substrates ADP and AMP are the most efficient counter-exchange substrates for NAD ؉ .Atndt1-and Atndt2-promoter-GUS plants demonstrate that both genes are strongly expressed in developing tissues and in particular in highly metabolically active cells. The presence of both carriers is discussed with respect to the subcellular localization of de novo NAD ؉ biosynthesis in plants and with respect to both the NAD ؉ -dependent metabolic pathways and the redox balance of chloroplasts and mitochondria.Nucleotides are metabolites of enormous importance for all living cells. They are the essential building blocks for DNA and RNA synthesis, energize most anabolic and many catabolic reactions, and fulfill critical functions in intracellular signal transduction (1, 2). Moreover, nucleotides serve as cofactors for a wide number of enzymes and are, with water, the most highly connected compounds within the metabolic network (3). Among these co-factors nicotinamide adenine dinucleotides are widely used for reductive/oxidative processes, playing important roles in the operation and control of a wide range of dehydrogenase activities. Accordingly, nucleotides are essential in nearly all cell organelles, and transport of these solutes into mitochondria, plastids, the endoplasmic reticulum, the Golgi apparatus, and peroxisomes has been observed (4 -7).Two types of nucleotide transport proteins have been identified to date at the molecular level: nucleotide transporter (NTT) 2 type carriers and members of the mitochondrial carrier family. The former transporters occur in plastids from all plants (8) and in a limited number of intracellular pathogenic bacteria (9). Most NTT-type carrier proteins catalyze an ATP/ADPϩP i counter-exchange mode of transport (10 -13), but several bacterial NTT proteins mediate either H ϩ /nucleotide transport or NAD ϩ /ADP counter-exchange (12,14,15). With the exception of the bacterial NAD ϩ /ADP carrier (14), all NTT proteins exhibit 12 predicted trans-membrane domains, whereas none of the NTT proteins share structural or domain similarities to members of the mitochondrial carrier family (11).Carriers belonging to the mitochondrial carrier family (MC...

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“…(ii) In the course of organelle evolution, most of the endosymbiont's genes were transferred to the host nucleus (5,6) and therefore plastids have to import the vast majority of their protein constituents as precursors in a posttranslational event from the cytosol. In consequence the outer and inner envelope membranes are equipped with abundant protein translocon complexes (7)(8)(9).…”

mentioning

confidence: 99%