Identification of chloroplast envelope proteins in close physical proximity to a partially translocated chimeric precursor protein.

Wu, Chengbiao; Seibert, Fabian S.; Ko, Kenton

doi:10.1016/s0021-9258(18)31630-2

Cited by 112 publications

(41 citation statements)

References 44 publications

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“…We reviewed the discovery and identification process of Tic40 and noted extreme confusion when Tic40 was first isolated. Originally, Tic40 in B. napus was described as Com44/Cim44 both at the outer‐ and inner‐envelope membranes of chloroplasts (Wu et al ., ; Ko et al ., ). Later, it was renamed Toc36, a 36 kDa TOC component at the outer‐envelope membrane (Pang et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Two young genes reshape a novel interaction network in Brassica napus

et al. 2019

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Summary New genes often drive the evolution of gene interaction networks. In Brassica napus, the widely used genic male sterile breeding system 7365ABC is controlled by two young genes, Bnams4b and BnaMs3. However, the interaction mechanism of these two young genes remains unclear. Here, we confirmed that Bnams4b interacts with the nuclear localised E3 ligase BRUTUS (BTS). Ectopic expression of AtBRUTUS (AtBTS) and comparison between Bnams4b‐transgenic Arabidopsis and bts mutants suggested that Bnams4b may drive translocation of BTS to cause various toxic defects. BnaMs3 gained an exclusive interaction with the plastid outer‐membrane translocon Toc33 compared with Bnams3 and AtTic40, and specifically compensated for the toxic effects of Bnams4b. Heat shock treatment also rescued the sterile phenotype, and high temperature suppressed the interaction between Bnams4b and BTS in yeast. Furthermore, the ubiquitin system and TOC (translocon at the outer envelope membrane of chloroplasts) component accumulation were affected in Bnams4b‐transgenic Arabidopsis plants. Taken together, these results indicate that new chimeric Bnams4b carries BTS from nucleus to chloroplast, which may disrupt the normal ubiquitin–proteasome system to cause toxic effects, and these defects can be compensated by BnaMs3−Toc33 interaction or environmental heat shock. It reveals a scenario in which two population‐specific coevolved young genes reshape a novel interaction network in plants.

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Section: Discussionmentioning

confidence: 97%

Two young genes reshape a novel interaction network in Brassica napus

et al. 2019

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“…Chaperones from the Hsp70 family play the important role during protein import into chloroplasts. The chloroplastic outer membrane protein 70 (Com70) is exposed on the cytoplasmic side of the membrane (Ko et al, 1992, Wu et al, 1994. The other, Hsp70 import-associated protein, faces the intermembrane space between the outer and inner envelope membranes (Marshall et al, 1990, Waegemann and Soll, 1991.…”

Section: Protein Import Into Chloroplastsmentioning

confidence: 99%

Protein import into chloroplasts

Soll

Schleiff

2004

Nat Rev Mol Cell Biol

370

187

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Der Import in Chloroplasten eines hybriden Konstrukts, das aus dem Transitpeptid von SSU, dem N-proximal Teil von maturem Tic110 und dem maturen SSU besteht, führte zum erscheinen eines löslichen stromalen Importintermediats und zu der Hypothese, dass Tic110 einen Reexport-Weg vom Stroma in die innere Hüllmembran verwenden könnte. Für das Volllängen-Protein Tic110 war kein lösliches Intermediat beobachtet worden. Eines der Ziele dieser Arbeit war den Importpfad von Tic110 ausführlicher untersuchen. In dieser Arbeit wurde das lösliche stromale Intermediat von Tic110 beobachtet, seine Re-Insertion in die Membran wurde verfolgt, und schließlich wurde das Intermediat isoliert und mit den stromalen Chaperonen Hsp93, Hsp70 und in einem kleineren Ausmaß Cpn60 coimmungefällt. Die erhaltenen Ergebnisse zeigen, dass Tic110, einen Reexport-Weg während seines Imports in die innere Hüllmembran von Chloroplasten verwendet. Tic110 benötigt stromale Chaperone, um seine native Konformation vor der Insertion in die innere Hüllmembran zu erreichen. Der Import mechanismus, der die Proteine zum Intermembranraum von Chloroplasten dirigiert, war noch nicht intensiv untersucht worden. Deshalb wurde der Import von zwei im Intermembranraum lokalisierten Proteinen analysiert: Tic22, ein 22 kDa Protein-Bestandteil des Tic-Komplexes, und MGD1, Synthase des MGDG, des häufigsten Galactolipid. Beide Proteine werden im Kern kodiert und an den Ribosomen im Cytosol mit einer spaltbaren N-terminalen Präsequenz synthetisiert. Tic22 bindet an die Außenseite der inneren Hüllmembran, und im geringerem Maße an die Innenseite der äußeren Hüllmembran. MGD1 scheint über elektrostatische Interaktionen mit den Hüllmembranen zu interagieren. Das Importverhalten von Tic22 und MGD1 und die Lokalisierung von MGD1 wurden in dieser Arbeit untersucht. Die hier präsentierten Ergebnisse zeigen, dass der Import von MGD1 von extern zugefügtem ATP abhängig ist im Gegensatz zu Tic22, dessen Importeffizienz in Anwesenheit von ATP zunimmt. Beide Vorstufenproteine benötigen Protease-sensitive Komponenten auf der Chloroplast-Oberfläche für den erfolgreichen Import. Chemische Quervernetzungen und Immunfällungen haben gezeigt, dass Tic22 und MGD1 während ihrer Translokation mit den Bestandteilen des Toc Komplexes interagieren. Importkompetitions-Experimente zeigten, dass beide Proteine die Toc Maschinerie des allgemeinen Importwegs verwenden. Daraus folgt, dass diese Proteine des Intermembranraums denselben Weg über die äußere Hüllmembran nutzen wie stromale Proteine.

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“…Two members of the hsp70 family of molecular chaperones, Corn70 (Wu et al, 1994) and the hsp70-IAP (Schnell et al, 1994), are also associated with an early import intermediate. Corn70 is peripherally associated with the cytosolic surface of the outer membrane (Wu et al, 1994).…”

mentioning

confidence: 99%

Two components of the chloroplast protein import apparatus, IAP86 and IAP75, interact with the transit sequence during the recognition and translocation of precursor proteins at the outer envelope.

Kouranov

LaSala

et al. 1996

The Journal of Cell Biology

167

223

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Abstract. The interactions of precursor proteins with components of the chloroplast envelope were investigated during the early stages of protein import using a chemical cross-linking strategy. In the absence of energy, two components of the outer envelope import machinery, IAP86 and IAP75, cross-linked to the transit sequence of the precursor to the small subunit of ribulose-l,5-bisphosphate carboxylase (pS) in a precursor binding assay. In the presence of concentrations of ATP or GTP that support maximal precursor binding to the envelope, cross-linking to the transit sequence occurred predominantly with IAP75 and a previously unidentified 21-kD polypeptide of the inner membrane, indicating that the transit sequence had inserted across the outer membrane. Cross-linking of envelope components to sequences in the mature portion of a second precursor, preferredoxin, was detected in the presence of ATP or GTP, suggesting that sequences distant from the transit sequence were brought into the vicinity of the outer membrane under these conditions. IAP75 and a third import component, IAP34, were coimmunoprecipitated with IAP86 antibodies from solubilized envelope membranes, indicating that these three proteins form a stable complex in the outer membrane. On the basis of these observations, we propose that IAP86 and IAP75 act as components of a multisubunit complex to mediate energy-independent recognition of the transit sequence and subsequent nucleoside triphosphateinduced insertion of the transit sequence across the outer membrane.

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Identification of chloroplast envelope proteins in close physical proximity to a partially translocated chimeric precursor protein.

Cited by 112 publications

References 44 publications

Two young genes reshape a novel interaction network in Brassica napus

Two young genes reshape a novel interaction network in Brassica napus

Protein import into chloroplasts

Two components of the chloroplast protein import apparatus, IAP86 and IAP75, interact with the transit sequence during the recognition and translocation of precursor proteins at the outer envelope.

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