scholarly journals The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP

2002 ◽  
Vol 159 (5) ◽  
pp. 833-843 ◽  
Author(s):  
Matthew D. Smith ◽  
Andreas Hiltbrunner ◽  
Felix Kessler ◽  
Danny J. Schnell
Keyword(s):  
Envelope Membrane ◽  
Outer Envelope ◽  
Gtpase Domain ◽  
Gtp Hydrolysis ◽  
Gtp Binding ◽  
Direct Binding ◽  
Outer Envelope Membrane ◽  
Preprotein Translocation ◽  
Initial Binding ◽  
Intrinsic Gtpase Activity

The multimeric translocon at the outer envelope membrane of chloroplasts (Toc) initiates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two Toc GTPases, Toc159 and Toc33/34, mediate preprotein recognition and regulate preprotein translocation. Although these two proteins account for the requirement of GTP hydrolysis for import, the functional significance of GTP binding and hydrolysis by either GTPase has not been defined. A recent study indicates that Toc159 is equally distributed between a soluble cytoplasmic form and a membrane-inserted form, raising the possibility that it might cycle between the cytoplasm and chloroplast as a soluble preprotein receptor. In the present study, we examined the mechanism of targeting and insertion of the Arabidopsis thaliana orthologue of Toc159, atToc159, to chloroplasts. Targeting of atToc159 to the outer envelope membrane is strictly dependent only on guanine nucleotides. Although GTP is not required for initial binding, the productive insertion and assembly of atToc159 into the Toc complex requires its intrinsic GTPase activity. Targeting is mediated by direct binding between the GTPase domain of atToc159 and the homologous GTPase domain of atToc33, the Arabidopsis Toc33/34 orthologue. Our findings demonstrate a role for the coordinate action of the Toc GTPases in assembly of the functional Toc complex at the chloroplast outer envelope membrane.

Detection of small GTP-binding proteins in the outer envelope membrane of pea chloroplasts

1992 ◽  
pp. 209-212
Author(s):  
Yukio Nagano ◽  
Kazumasa Sekiguchi ◽  
Nobuhiko Mural ◽  
Ryuichi Matsuno ◽  
Yukiko Sasaki
Keyword(s):  
Binding Proteins ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Outer Envelope Membrane

Detection of small GTP-binding proteins in the outer envelope membrane of pea chloroplasts

FEBS Letters ◽  
1991 ◽  
Vol 293 (1-2) ◽  
pp. 124-126 ◽  
Author(s):  
Yukiko Sasaki ◽  
Kazumasa Sekiguchi ◽  
Yukio Nagano ◽  
Ryuichi Matsuno
Keyword(s):  
Binding Proteins ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Outer Envelope Membrane

scholarly journals Insertion of plastidic β-barrel proteins into the outer envelopes of plastids involves an intermembrane space intermediate formed with Toc75-V/OEP80

2021 ◽  
Author(s):  
Lucia E Gross ◽  
Anna Klinger ◽  
Nicole Spies ◽  
Theresa Ernst ◽  
Nadine Flinner ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Import ◽  
Membrane Insertion ◽  
Intermembrane Space ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Pea Proteins ◽  
Outer Envelope Membrane ◽  
Correct Topology ◽  
Shed Light

Abstract The insertion of organellar membrane proteins with the correct topology requires the following: First, the proteins must contain topogenic signals for translocation across and insertion into the membrane. Second, proteinaceous complexes in the cytoplasm, membrane, and lumen of organelles are required to drive this process. Many complexes required for the intracellular distribution of membrane proteins have been described, but the signals and components required for the insertion of plastidic β-barrel-type proteins into the outer membrane are largely unknown. The discovery of common principles is difficult, as only a few plastidic β-barrel proteins exist. Here, we provide evidence that the plastidic outer envelope β-barrel proteins OEP21, OEP24, and OEP37 from pea (Pisum sativum) and Arabidopsis thaliana contain information defining the topology of the protein. The information required for translocation of pea proteins across the outer envelope membrane is present within the six N-terminal β-strands. This process requires the action of TOC (translocon of the outer chloroplast membrane). After translocation into the intermembrane space, β-barrel proteins interact with TOC75-V, as exemplified by OEP37 and P39, and are integrated into the membrane. The membrane insertion of plastidic β-barrel proteins is affected by mutation of the last β-strand, suggesting that this strand contributes to the insertion signal. These findings shed light on the elements and complexes involved in plastidic β-barrel protein import.

Mechanism of protein import across the chloroplast envelope

2000 ◽  
Vol 28 (4) ◽  
pp. 485-491 ◽  
Author(s):  
K. Chen ◽  
X. Chen ◽  
D. J. Schnell
Keyword(s):  
Protein Import ◽  
Essential Elements ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Subunits ◽  
Targeting Signals ◽  
Outer Envelope Membrane ◽  
Envelope Membranes

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toe apparatus) and inner (Tic apparatus) envelope membranes.

scholarly journals Spinach hexokinase I is located in the outer envelope membrane of plastids

FEBS Letters ◽  
1999 ◽  
Vol 461 (1-2) ◽  
pp. 13-18 ◽  
Author(s):  
Anika Wiese ◽  
Ferdi Gröner ◽  
Uwe Sonnewald ◽  
Heike Deppner ◽  
Jens Lerchl ◽  
...  
Keyword(s):  
Envelope Membrane ◽  
Outer Envelope ◽  
Outer Envelope Membrane

scholarly journals Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

2016 ◽  
Vol 113 (38) ◽  
pp. 10714-10719 ◽  
Author(s):  
Amélie A. Kelly ◽  
Barbara Kalisch ◽  
Georg Hölzl ◽  
Sandra Schulze ◽  
Juliane Thiele ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Lipid Transfer ◽  
Terminal Sequence ◽  
Outer Envelope ◽  
Outer Envelope Membrane ◽  
Envelope Reconstruction ◽  
Envelope Membranes

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.

scholarly journals Lipids Guide the Way: Targeting Proteins to the Chloroplast Outer Envelope Membrane

2014 ◽  
Vol 30 (5) ◽  
pp. 493-495
Author(s):  
Lynn G.L. Richardson ◽  
Yamuna D. Paila ◽  
Danny J. Schnell
Keyword(s):  
Envelope Membrane ◽  
Outer Envelope ◽  
Outer Envelope Membrane ◽  
The Way
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