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Université de Neuchâtel

The Novel Chloroplast Outer Membrane Kinase KOC1 Is a Required Component of the Plastid Protein Import Machinery

Zufferey, Mónica ; Montandon, Cyrille ; Douet, Véronique ; Demarsy, Emilie ; Agne, Birgit ; Baginsky, Sacha ; Kessler, Felix

In: Journal of biological chemistry, 2017, vol. 292, no. 17, p. 6952-6964

The biogenesis and maintenance of cell organelles such as mitochondria and chloroplasts require the import of many proteins from the cytosol, a process that is controlled by phosphorylation. In the case of chloroplasts, the import of hundreds of different proteins depends on translocons at the outer and inner chloroplast membrane (TOC and TIC, respectively) complexes. The essential protein TOC159...

Université de Neuchâtel

The Acidic A-Domain of Arabidopsis Toc159 Occurs as a Hyperphosphorylated Protein

Agne, Birgit ; Andrès, Charles ; Montandon, Cyril ; Christ, Bastien ; Ertan, Anouk ; Jung, Friederike ; Infanger, Sibylle ; Bischof, Sylvain ; Baginsky, Sacha ; Kessler, Felix

In: Plant Physiology, 2010, vol. 53, no. 3, p. 1016-1030

The translocon at the outer membrane of the chloroplast assists the import of a large class of preproteins with amino-terminal transit sequences. The preprotein receptors Toc159 and Toc33 in Arabidopsis (Arabidopsis thaliana) are specific for the accumulation of abundant photosynthetic proteins. The receptors are homologous GTPases known to be regulated by phosphorylation within their...

Université de Neuchâtel

Characterization of Chloroplast Protein Import without Tic56, a Component of the 1-Megadalton Translocon at the Inner Envelope Membrane of Chloroplasts

Köhler, Daniel ; Montandon, Cyril ; Hause, Gerd ; Majovsky, Petra ; Kessler, Felix ; Baginsky, Sacha ; Agne, Birgit

In: Plant Physiology, 2015, vol. 167, no. 3, p. 972-990

We report on the characterization of Tic56, a unique component of the recently identified 1-MD translocon at the inner envelope membrane of chloroplasts (TIC) in Arabidopsis (Arabidopsis thaliana) comprising Tic20, Tic100, and Tic214. We isolated Tic56 by copurification with Tandem Affinity Purification-tagged Toc159 in the absence of precursor protein, indicating spontaneous and...

Université de Neuchâtel

The Chloroplast Import Receptor Toc90 Partially Restores the Accumulation of Toc159 Client Proteins in the Arabidopsis thaliana ppi2 Mutant

Infanger, Sibylle ; Bischof, Sylvain ; Hiltbrunner, Andreas ; Agne, Birgit ; Baginsky, Sacha ; Kessler, Felix

In: Molecular Plant, 2011, vol. 4, no. 2, p. 252–263

Successful import of hundreds of nucleus-encoded proteins is essential for chloroplast biogenesis. The import of cytosolic precursor proteins relies on the Toc- (translocon at the outer chloroplast membrane) and Tic- (translocon at the inner chloroplast membrane) complexes. In Arabidopsis thaliana, precursor recognition is mainly mediated by outer membrane receptors belonging to two...

Université de Neuchâtel

Nucleotide binding and dimerization at the chloroplast pre-protein import receptor, atToc33, are not essential in vivo but do increase import efficiency

Aronsson, Henrik ; Combe, Jonathan ; Patel, Ramesh ; Agne, Birgit ; Martin, Meryll ; Kessler, Felix ; Jarvis, Paul

In: The Plant Journal, 2010, vol. 63, no. 2, p. 297-311

The atToc33 protein is one of several pre-protein import receptors in the outer envelope of Arabidopsis chloroplasts. It is a GTPase with motifs characteristic of such proteins, and its loss in the plastid protein import 1 (ppi1) mutant interferes with the import of photosynthesis-related pre-proteins, causing a chlorotic phenotype in mutant plants. To assess the significance of GTPase...

Université de Neuchâtel

The TOC complex: Preprotein gateway to the chloroplast

Andrès, Charles ; Agne, Birgit ; Kessler, Felix

In: Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2010, vol. 1803, no. 6, p. 715-723

Photosynthetic eukaryotes strongly depend on chloroplast metabolic pathways. Most if not all involve nuclear encoded proteins. These are synthesized as cytosolic preproteins with N-terminal, cleavable targeting sequences (transit peptide). Preproteins are imported by a major pathway composed of two proteins complexes: TOC and TIC (Translocon of the Outer and Inner membranes of the...

Université de Neuchâtel

Pheophytin Pheophorbide Hydrolase (Pheophytinase) Is Involved in Chlorophyll Breakdown during Leaf Senescence in Arabidopsis[W],[OA]

Schelbert, Silvia ; Aubry, Sylvain ; Burla, Bo ; Agne, Birgit ; Kessler, Felix ; Krupinska, Karin ; Hörtensteiner, Stefan

In: The Plant Cell, 2009, vol. 21, no. 3, p. 767-785

During leaf senescence, chlorophyll is removed from thylakoid membranes and converted in a multistep pathway to colorless breakdown products that are stored in vacuoles. Dephytylation, an early step of this pathway, increases water solubility of the breakdown products. It is widely accepted that chlorophyll is converted into pheophorbide via chlorophyllide. However, chlorophyllase, which converts...

Université de Neuchâtel

In vivo interaction between atToc33 and atToc159 GTP-binding domains demonstrated in a plant split-ubiquitin system

Rahim, Gwendoline ; Bischof, Sylvain ; Kessler, Felix ; Agne, Birgit

In: Journal of Experimental Botany, 2008, vol. 60, no. 1, p. 257-267

The GTPases atToc33 and atToc159 are pre-protein receptor components of the translocon complex at the outer chloroplast membrane in Arabidopsis. Despite their participation in the same complex in vivo;, evidence for their interaction is still lacking. Here, a split-ubiquitin system is engineered for use in plants, and the in vivo; interaction of the Toc GTPases...

Université de Neuchâtel

The role of GTP binding and hydrolysis at the atToc159 preprotein receptor during protein import into chloroplasts

Wang, Fei ; Agne, Birgit ; Kessler, Felix ; Schnell, Danny J.

In: The Journal of Cell Biology, 2008, vol. 183, no. 1, p. 87-99

The majority of nucleus-encoded chloroplast proteins are targeted to the organelle by direct binding to two membrane-bound GTPase receptors, Toc34 and Toc159. The GTPase activities of the receptors are implicated in two key import activities, preprotein binding and driving membrane translocation, but their precise functions have not been defined. We use a combination of in vivo and in vitro...