Molecular interactions within the plant TOC complex

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Maik S. Sommer ◽  
Enrico Schleiff
Keyword(s):  
Molecular Interactions ◽  
Protein Transport ◽  
Protein Import ◽  
Current Knowledge ◽  
Transport Processes ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Molecules ◽  
Membrane Bound ◽  
Cellular Compartments

Abstract Protein transport, especially into different cellular compartments, is a highly coordinated and regulated process. The molecular machineries which carry out these transport processes are highly complex in structure, function, and regulation. In the case of chloroplasts, thousands of protein molecules have been estimated to be transported across the double-membrane bound envelope per minute. In this brief review, we summarize current knowledge about the molecular interplay during precursor protein import into chloroplasts, focusing on the initial events at the outer envelope.

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 Protein partners of dynamin-1 in the retina

2013 ◽  
Vol 30 (4) ◽  
pp. 129-139 ◽  
Author(s):  
GREGORY H. GROSSMAN ◽  
LINDSEY A. EBKE ◽  
CRAIG D. BEIGHT ◽  
GEENG-FU JANG ◽  
JOHN W. CRABB ◽  
...  
Keyword(s):  
Protein Transport ◽  
Plexiform Layer ◽  
Specific Protein ◽  
Membrane Dynamics ◽  
Second Order ◽  
Transport Processes ◽  
Mouse Retina ◽  
Inner Plexiform Layer ◽  
Cellular Compartments ◽  
Dynamin 2

AbstractDynamin proteins are involved in vesicle generation, providing mechanical force to excise newly formed vesicles from membranes of cellular compartments. In the brain, dynamin-1, dynamin-2, and dynamin-3 have been well studied; however, their function in the retina remains elusive. A retina-specific splice variant of dynamin-1 interacts with the photoreceptor-specific protein Tubby-like protein 1 (Tulp1), which when mutated causes an early onset form of autosomal recessive retinitis pigmentosa. Here, we investigated the role of the dynamins in the retina, using immunohistochemistry to localize dynamin-1, dynamin-2, and dynamin-3 and immunoprecipitation followed by mass spectrometry to explore dynamin-1 interacting proteins in mouse retina. Dynamin-2 is primarily confined to the inner segment compartment of photoreceptors, suggesting a role in outer segment protein transport. Dynamin-3 is present in the terminals of photoreceptors and dendrites of second-order neurons but is most pronounced in the inner plexiform layer where second-order neurons relay signals from photoreceptors. Dynamin-1 appears to be the dominant isoform in the retina and is present throughout the retina and in multiple compartments of the photoreceptor cell. This suggests that it may function in multiple cellular pathways. Surprisingly, dynamin-1 expression and localization did not appear to be disrupted in tulp1−/− mice. Immunoprecipitation experiments reveal that dynamin-1 associates primarily with proteins involved in cytoskeletal-based membrane dynamics. This finding is confirmed by western blot analysis. Results further implicate dynamin-1 in vesicular protein transport processes relevant to synaptic and post-Golgi pathways and indicate a possible role in photoreceptor stability.

Protein transport across the peroxisomal membrane

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Wolfgang Girzalsky ◽  
Harald W. Platta ◽  
Ralf Erdmann
Keyword(s):  
Protein Transport ◽  
Protein Import ◽  
Current Knowledge ◽  
Soluble Proteins ◽  
Matrix Proteins ◽  
Peroxisomal Membrane ◽  
Oligomeric Proteins ◽  
Peroxisomal Protein ◽  
Polypeptide Chains

AbstractThe maintenance of peroxisome function depends on the formation of the peroxisomal membrane and the subsequent import of both membrane and matrix proteins. Without exception, peroxisomal matrix proteins are nuclear encoded, synthesized on free ribosomes and subsequently imported post-translationally. In contrast to other translocation systems that transport unfolded polypeptide chains, the peroxisomal import apparatus can facilitate the transport of folded and oligomeric proteins across the peroxisomal membrane. The peroxisomal protein import is mediated by cycling receptors that shuttle between the cytosol and peroxisomal lumen and depends on ATP and ubiquitin. In this brief review, we will summarize our current knowledge on the import of soluble proteins into the peroxisomal matrix.

ATP-driven processes of peroxisomal matrix protein import

2017 ◽  
Vol 398 (5-6) ◽  
pp. 607-624 ◽  
Author(s):  
Daniel P. Schwerter ◽  
Immanuel Grimm ◽  
Harald W. Platta ◽  
Ralf Erdmann
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Atp Hydrolysis ◽  
Current Knowledge ◽  
Model Organism ◽  
Peroxisomal Membrane ◽  
Dual Localization ◽  
Import Receptors ◽  
Membrane Bound ◽  
Atp Binding And Hydrolysis

Abstract In peroxisomal matrix protein import two processes directly depend on the binding and hydrolysis of ATP, both taking place at the late steps of the peroxisomal import cycle. First, ATP hydrolysis is required to initiate a ubiquitin-transfer cascade to modify the import (co-)receptors. These receptors display a dual localization in the cytosol and at the peroxisomal membrane, whereas only the membrane bound fraction receives the ubiquitin modification. The second ATP-dependent process of the import cycle is carried out by the two AAA+-proteins Pex1p and Pex6p. These ATPases form a heterohexameric complex, which is recruited to the peroxisomal import machinery by the membrane anchor protein Pex15p. The Pex1p/Pex6p complex recognizes the ubiquitinated import receptors, pulls them out of the membrane and releases them into the cytosol. There the deubiquitinated receptors are provided for further rounds of import. ATP binding and hydrolysis are required for Pex1p/Pex6p complex formation and receptor export. In this review, we summarize the current knowledge on the peroxisomal import cascade. In particular, we will focus on the ATP-dependent processes, which are so far best understood in the model organism Saccharomyces cerevisiae.

Topology Studies of the Chloroplast Protein Import Channel Toc75

2000 ◽  
Vol 381 (8) ◽  
pp. 687-693 ◽  
Author(s):  
N. Sveshnikova ◽  
R. Grimm ◽  
J. Soll ◽  
E. Schleiff
Keyword(s):  
Protein Transport ◽  
Protein Import ◽  
Computer Modelling ◽  
Protein Structures ◽  
Beta Sheets ◽  
Proteolytic Digestion ◽  
Major Goal ◽  
Amino Acid Sequencing ◽  
Outer Envelope ◽  
Topology Model

Abstract A major goal in understanding protein transport across membranes is the investigation of the structure and regulation of the translocon subunits. We analysed Toc75, a pore-forming subunit of the translocon of the outer envelope of chloroplasts. Toc75 was over-expressed and reconstituted into liposomes. Immunoprecipitation of liposome-reconstituted Toc75 indicates an Nin-Cin orientation of Toc75. Limited proteolytic digestion of Toc75 present in outer envelope vesicles with specific proteases combined with amino acid sequencing was used to study the topology of Toc75. Finally, computer modelling based on known protein structures indicates that Toc75 traverses the outer envelope with 16 amphiphilic beta sheets and the topology model is presented.

Protein trafficking to plastids: one theme, many variations

2008 ◽  
Vol 413 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Takehito Inaba ◽  
Danny J. Schnell
Keyword(s):  
Gene Expression ◽  
Plant Development ◽  
Protein Trafficking ◽  
Protein Import ◽  
Current Knowledge ◽  
Regulatory Mechanisms ◽  
Diverse Group ◽  
Double Membrane ◽  
Plastid Envelope ◽  
Plastid Protein

Plastids are a diverse group of essential organelles in plants that include chloroplasts. The biogenesis and maintenance of these organelles relies on the import of thousands of nucleus-encoded proteins. The complexity of plastid structure has resulted in the evolution of at least four general import pathways that target proteins into and across the double membrane of the plastid envelope. Several of these pathways can be further divided into specialty pathways that mediate and regulate the import of specific classes of proteins. The co-ordination of import by these specialized pathways with changes in gene expression is critical for plastid and plant development. Moreover, protein import is acutely regulated in response to physiological and metabolic changes within the cell. In the present review we summarize the current knowledge of the mechanism of import via these pathways and highlight the regulatory mechanisms that integrate the plastid protein-trafficking pathways with the developmental and metabolic state of the plant.

The ultrastructure of the double membrane-bound bodies and endoplasmic reticulum in serial sections of wheat spot mosaic-affected wheat plants

1990 ◽  
Vol 48 (3) ◽  
pp. 694-695
Author(s):  
M. H. Chen ◽  
C. Hiruki
Keyword(s):  
Endoplasmic Reticulum ◽  
High Resolution ◽  
Membrane Structure ◽  
Mosaic Disease ◽  
Serial Sections ◽  
Thin Sections ◽  
Double Membrane ◽  
Southern Alberta ◽  
Membrane Bound ◽  
Scanning Em

Wheat spot mosaic disease was first discovered in southern Alberta, Canada, in 1956. A hitherto unidentified disease-causing agent, transmitted by the eriophyid mite, caused chlorosis, stunting and finally severe necrosis resulting in the death of the affected plants. Double membrane-bound bodies (DMBB), 0.1-0.2 μm in diameter were found to be associated with the disease.Young tissues of leaf and root from 4-wk-old infected wheat plants were fixed, dehydrated, and embedded in Spurr’s resin. Serial sections were collected on slot copper grids and stained. The thin sections were then examined with a Hitachi H-7000 TEM at 75 kV. The membrane structure of the DMBBs was studied by numbering them individually and tracing along the sections to see any physical connection with endoplasmic reticulum (ER) membranes. For high resolution scanning EM, a modification of Tanaka’s method was used. The specimens were examined with a Hitachi Model S-570 SEM in its high resolution mode at 20 kV.

Portein-gold labelling of ultrathin sections of wheat spot mosaic-affected wheat plants

1990 ◽  
Vol 48 (3) ◽  
pp. 680-681
Author(s):  
K. S. Zaychuk ◽  
M. H. Chen ◽  
C. Hiruki
Keyword(s):  
Osmium Tetroxide ◽  
Rnase A ◽  
Leaf Ultrastructure ◽  
Double Membrane ◽  
Young Root ◽  
Leaf Tissues ◽  
Membrane Bound ◽  
Ultrathin Sections ◽  
Gold Labelling ◽  
Electron Dense Core

Wheat spot mosaic (WSpM), which frequently occurs with wheat streak mosaic virus was first reported in 1956 from Alberta. Singly isolated, WSpM causes chlorotic spots, chlorosis, stunting, and sometimes death of the wheat plants. The vector responsible for transmission is the eriophyid mite, Eriophyes tulipae Kiefer. The examination of leaf ultrastructure by electron microscopy has revealed double membrane bound bodies (DMBB’s) 0.1-0.2 μm in diameter. Dispersed fibrils within these bodies suggested the presence of nucleic acid. However, neither ribosomes characteristic of bacteria, mycoplasma and the psittacosis group of organisms nor an electron dense core characteristic of many viruses was commonly evident.In an attempt to determine if the DMBB’s contain nucleic acids, RNase A, DNase I, and lactoferrin protein were conjugated with 10 nm colloidal gold as previously described. Young root and leaf tissues from WSpM-affected wheat plants were fixed in glutaraldehyde, postfixed in osmium tetroxide,and embedded in Spurr’s resin.

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.

Single- or double-membrane-bound vesicles and P, Ca, and Fe-containing granules in Xanthomonas citri cultured on a solid medium

Micron ◽  
2021 ◽  
Vol 143 ◽  
pp. 103024
Author(s):  
Junhyung Park ◽  
A Reum Je ◽  
Sang Gil Lee ◽  
Jae Hyuck Jang ◽  
Yang Hoon Huh ◽  
...  
Keyword(s):  
Solid Medium ◽  
Xanthomonas Citri ◽  
Double Membrane ◽  
Membrane Bound
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