A plastid enzyme arrested in the step of precursor translocation in vivo.

Reinbothe, Steffen; Reinbothe, Christiane; Neumann, D.; Apel, Klaus

doi:10.1073/pnas.93.21.12026

Cited by 29 publications

(31 citation statements)

References 52 publications

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“…1, lanes g and h versus e and f and SI Fig. 8A, lanes [11][12][13][14][15][16][17][18][19][20], we assumed that a factor may be present in wheat germ extract that triggered substrate-independent import of pPORA. Consistent with this view, import of reticulocytetranslated pPORA into Pchlide-free chloroplasts could be rescued by addition of wheat germ extract (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Ivanova et al (12) and Kubis et al (13) discovered that the main presequence receptor atToc159 interacts with precursors to photosynthetic proteins, but it displayed little activity in binding assays with nonphotosynthetic precursors including that of NADPH:protochlorophyllide (Pchlide) oxidoreductase A (pPORA) (14). Import of this nucleus-encoded enzyme was shown to depend on the presence of Pchlide (15)(16)(17) and involve a translocon not identical with the Toc159-and Toc75-containing translocon used by photosynthetic precursors (18)(19)(20). Biochemical studies identified the pPORA translocon to consist of several unique components, called Pchlide-dependent translocon (Ptc) proteins, of which Ptc52 most likely operated as a Pchlide a oxygenase.…”

mentioning

confidence: 99%

“…Biochemical studies identified the pPORA translocon to consist of several unique components, called Pchlide-dependent translocon (Ptc) proteins, of which Ptc52 most likely operated as a Pchlide a oxygenase. The detection of such activity would imply a tight coupling of tetrapyrrole precursor biosynthesis and protein import and suggest a photoprotective role of the Pchlide-dependent pPORA import pathway for plant de-etiolation (15)(16)(17)(18)(19)(20).…”

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confidence: 99%

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A substrate-independent, 14:3:3 protein-mediated plastid import pathway of NADPH:protochlorophyllide oxidoreductase A

Schemenewitz

Pollmann²,

Reinbothe³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Plastids are semiautonomous organelles that contain only limited coding information in their own DNA. Because most of their genome was transferred to the nucleus after their endosymbiotic origin, plastids must import the major part of their protein constituents from the cytosol. The exact role of cytosolic targeting factors in the regulation of plastid protein import has not been determined. Here, we report that the nucleus-encoded NADPH: protochlorophyllide (Pchlide) oxidoreductase A plastid precursor (pPORA) can use two different plastid import pathways that differ by the requirements for cytosolic 14:3:3 proteins and Hsp70. pPORA synthesized in a wheat germ lysate segregated into different precursor fractions. While import of free pPORA and only Hsp70-complexed pPORA was Pchlide-dependent and involved the previously identified Pchlide-dependent translocon, 14:3:3 proteinand Hsp70-complexed pPORA was transported into Pchlide-free chloroplasts through the Toc75-containing standard translocon at the outer chloroplast membrane/translocon at the inner chloroplast membrane machinery. A 14:3:3 protein binding site was identified in the mature region of the 35 S-pPORA, which governed 14:3:3 protein-and Hsp70-mediated, Pchlide-independent plastid import. Collectively, our results reveal that the import of pPORA into the plastids is tightly regulated and involves different cytosolic targeting factors and plastid envelope translocon complexes.barley ͉ chloroplast biogenesis ͉ guidance complex ͉ protein import

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A substrate-independent, 14:3:3 protein-mediated plastid import pathway of NADPH:protochlorophyllide oxidoreductase A

Schemenewitz

Pollmann²,

Reinbothe³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…According to previous work, this 44-kDa protein most likely represented the cytosolic precursor of the pPORA (14). Import of this nucleusencoded plastid protein requires protochlorophyllide (Pchlide) (14)(15)(16)(17) and is due to the operation of an import pathway that has been proposed to be unique compared with the import pathways of other precursors (18).…”

mentioning

confidence: 99%

The outer plastid envelope protein Oep16: Role as precursor translocase in import of protochlorophyllide oxidoreductase A

Reinbothe

Quigley

Springer

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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A 16-kDa plastid envelope protein was identified by chemical crosslinking that interacts with the precursor of NADPH:protochlorophyllide oxdidoreductase A (pPORA) during its posttranslational import into isolated barley chloroplasts. Protein purification and subsequent protein sequencing showed that the 16-kDa protein is an ortholog of a previously identified outer plastid envelope protein, Oep16. A protein of identical size was present in barley etioplasts and interacted with pPORA. Similar 16-kDa proteindependent crosslink products of pPORA were detected in wheat, pea, and Arabidopsis chloroplasts. Database analyses revealed that the 16-kDa protein belongs to a family of preprotein and amino acid transporters found in free-living bacteria and endosymbiotic mitochondria and chloroplasts. Antibodies raised against the 16-kDa protein inhibited import of pPORA, highlighting its role in protein import.

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“…IB demonstrates that three POR-related proteins could be detected, displaying molecular masses of 44, 38 and 36kDa, respectively. According to our previous studies [24,46], these POR proteins were likely to represent the cytosolic precursor of the PORA, pPORA (44kDa), the mature PORB (38kDa) and the mature PORA (36kDa). Large-scale isolation from múltiple gels of the 44, 38 and 36kDa bands plus subsequent sequencing of proteolytic fragments generated with cyanogen bromide or different proteases confirmed that the 44kDa protein indeed represents the pPORA and its mature, 36kDa form, whereas the partial sequence information for the 38kDa band demonstrated that it is identical with PORB (Fig.…”

Section: Pora and Porb Are Developmentally Expressed Across The Barlementioning

confidence: 99%

LHPP, the light-harvesting NADPH:protochlorophyllide (Pchlide) oxidoreductase:Pchlide complex of etiolated plants, is developmentally expressed across the barley leaf gradient

et al. 2004

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NADPH:protochlorophyllide oxidoreductase is a key enzyme for the light-induced greening of etiolated angiosperm plants. In barley, two POR proteins exist termed PORA and PORB that have previously been proposed to stmcturally and functionally cooperate in terms of a higher molecular mass light-harvesting complex named LHPP, in the prolamellar body of etioplasts [Nature 397 (1999) 80]. In this study we examined the expression pattern of LHPP during seedling etiolation and de-etiolation under different experimental conditions. Our results show that LHPP is developmentally expressed across the barley leaf gradient. We further provide evidence that LHPP operates both in plants that etiolate completely before being exposed to white light and in plants that etiolate only partially and begin light-harvesting as soon as traces of light become available in the uppermost parts of the soil. As a result of light absorption, in either case LHPP converts Pchlide a to chlorophyllide (Chlide) a and in turn disintegrates. The released Chlide a, as well as Chlide b produced upon LHPP's light-dependent dissociation, which leads to the activation of the PORA as a Pchlide £-reducing enzyme, then bind to homologs of water-soluble chlorophyll proteins of Brassicaceae. We propose that these proteins transfer Chlide a and Chlide b\o the thylakoids, where their esterification with phytol and assembly into the photosynthetic membrane complexes ultimately takes place. Presumably due to the tight coupling of LHPP synthesis and degradation, as well as WSCP formation and photosynthetic membrane assembly, eflficient photo-protection is conferred onto the plant.

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A plastid enzyme arrested in the step of precursor translocation in vivo.

Abstract: The key enzyme of chlorophyll biosynthesis in higher plants, NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR, EC 1.3

Cited by 29 publications

References 52 publications

A substrate-independent, 14:3:3 protein-mediated plastid import pathway of NADPH:protochlorophyllide oxidoreductase A

A substrate-independent, 14:3:3 protein-mediated plastid import pathway of NADPH:protochlorophyllide oxidoreductase A

The outer plastid envelope protein Oep16: Role as precursor translocase in import of protochlorophyllide oxidoreductase A

LHPP, the light-harvesting NADPH:protochlorophyllide (Pchlide) oxidoreductase:Pchlide complex of etiolated plants, is developmentally expressed across the barley leaf gradient

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