scholarly journals A novel DNA import system

2016 ◽  
Vol 14 (4) ◽  
pp. 193-193
Author(s):  
Andrea Du Toit
Keyword(s):  
Import System

scholarly journals Peroxisome protein import recapitulated in Xenopus egg extracts

2019 ◽  
Vol 218 (6) ◽  
pp. 2021-2034 ◽  
Author(s):  
Fabian B. Romano ◽  
Neil B. Blok ◽  
Tom A. Rapoport
Keyword(s):  
Strong Evidence ◽  
Protein Import ◽  
Atp Hydrolysis ◽  
In Vitro Assay ◽  
Vitro Assay ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
Import System

Peroxisomes import their luminal proteins from the cytosol. Most substrates contain a C-terminal Ser-Lys-Leu (SKL) sequence that is recognized by the receptor Pex5. Pex5 binds to peroxisomes via a docking complex containing Pex14, and recycles back into the cytosol following its mono-ubiquitination at a conserved Cys residue. The mechanism of peroxisome protein import remains incompletely understood. Here, we developed an in vitro import system based on Xenopus egg extracts. Import is dependent on the SKL motif in the substrate and on the presence of Pex5 and Pex14, and is sustained by ATP hydrolysis. A protein lacking an SKL sequence can be coimported, providing strong evidence for import of a folded protein. The conserved cysteine in Pex5 is not essential for import or to clear import sites for subsequent rounds of translocation. This new in vitro assay will be useful for further dissecting the mechanism of peroxisome protein import.

scholarly journals The Protein Import System of Mitochondria

1996 ◽  
Vol 271 (50) ◽  
pp. 31763-31766 ◽  
Author(s):  
Gottfried Schatz
Keyword(s):  
Protein Import ◽  
Import System

scholarly journals Nuclear Import of Ho Endonuclease Utilizes Two Nuclear Localization Signals and Four Importins of the Ribosomal Import System

2006 ◽  
Vol 281 (18) ◽  
pp. 12218-12226 ◽  
Author(s):  
Anya Bakhrat ◽  
Keren Baranes ◽  
Oleg Krichevsky ◽  
Inna Rom ◽  
Gabriel Schlenstedt ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Localization Signals ◽  
Import System

scholarly journals Intercellular Diffusion of a Fluorescent Sucrose Analog via the Septal Junctions in a Filamentous Cyanobacterium

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Dennis J. Nürnberg ◽  
Vicente Mariscal ◽  
Jan Bornikoel ◽  
Mercedes Nieves-Morión ◽  
Norbert Krauß ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Cell Types ◽  
Cell Junctions ◽  
Filamentous Cyanobacterium ◽  
Nitrogen Fixing ◽  
Filamentous Cyanobacteria ◽  
Triple Mutant ◽  
Vegetative Cells ◽  
Metabolite Exchange ◽  
Import System

ABSTRACTMany filamentous cyanobacteria produce specialized nitrogen-fixing cells called heterocysts, which are located at semiregular intervals along the filament with about 10 to 20 photosynthetic vegetative cells in between. Nitrogen fixation in these complex multicellular bacteria depends on metabolite exchange between the two cell types, with the heterocysts supplying combined-nitrogen compounds but dependent on the vegetative cells for photosynthetically produced carbon compounds. Here, we used a fluorescent tracer to probe intercellular metabolite exchange in the filamentous heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. We show that esculin, a fluorescent sucrose analog, is incorporated by a sucrose import system into the cytoplasm of Anabaena cells. The cytoplasmic esculin is rapidly and reversibly exchanged across vegetative-vegetative and vegetative-heterocyst cell junctions. Our measurements reveal the kinetics of esculin exchange and also show that intercellular metabolic communication is lost in a significant fraction of older heterocysts. SepJ, FraC, and FraD are proteins located at the intercellular septa and are suggested to form structures analogous to gap junctions. We show that a ΔsepJΔfraCΔfraDtriple mutant shows an altered septum structure with thinner septa but a denser peptidoglycan layer. Intercellular diffusion of esculin and fluorescein derivatives is impaired in this mutant, which also shows a greatly reduced frequency of nanopores in the intercellular septal cross walls. These findings suggest that FraC, FraD, and SepJ are important for the formation of junctional structures that constitute the major pathway for feeding heterocysts with sucrose.IMPORTANCEAnabaena and its relatives are filamentous cyanobacteria that exhibit a sophisticated form of prokaryotic multicellularity, with the formation of differentiated cell types, including normal photosynthetic cells and specialized nitrogen-fixing cells called heterocysts. The question of how heterocysts communicate and exchange metabolites with other cells in the filament is key to understanding this form of bacterial multicellularity. Here we provide the first information on the intercellular exchange of a physiologically important molecule, sucrose. We show that a fluorescent sucrose analog can be imported into the Anabaena cytoplasm by a sucrose import system. Once in the cytoplasm, it is rapidly and reversibly exchanged among all of the cells in the filament by diffusion across the septal junctions. Photosynthetically produced sucrose likely follows the same route from cytoplasm to cytoplasm. We identify some of the septal proteins involved in sucrose exchange, and our results indicate that these proteins form structures functionally analogous to metazoan gap junctions.

scholarly journals Origin and Evolutionary Alteration of the Mitochondrial Import System in Eukaryotic Lineages

2017 ◽  
Vol 34 (7) ◽  
pp. 1574-1586 ◽  
Author(s):  
Yoshinori Fukasawa ◽  
Toshiyuki Oda ◽  
Kentaro Tomii ◽  
Kenichiro Imai
Keyword(s):  
Mitochondrial Import ◽  
Import System

scholarly journals Crystal structure of β-L-arabinobiosidase belonging to glycoside hydrolase family 121

2020 ◽  
Author(s):  
Keita Saito ◽  
Alexander Holm Viborg ◽  
Shiho Sakamoto ◽  
Takatoshi Arakawa ◽  
Chihaya Yamada ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Glycoside Hydrolase ◽  
Plant Pathogens ◽  
Catalytic Domain ◽  
Bifidobacterium Longum ◽  
Degradation Pathway ◽  
Site Directed Mutagenesis ◽  
Dimensional Structure ◽  
Glycoside Hydrolase Family ◽  
Import System

AbstractEnzymes acting on α-L-arabinofuranosides have been extensively studied; however, the structures and functions of β-L-arabinofuranosidases are not fully understood. Three enzymes and an ABC transporter in a gene cluster of Bifidobacterium longum JCM 1217 constitute a degradation and import system of β-L-arabinooligosaccharides on plant hydroxyproline-rich glycoproteins. An extracellular β-L-arabinobiosidase (HypBA2) belonging to the glycoside hydrolase (GH) family 121 plays a key role in the degradation pathway by releasing β-1,2-linked arabinofuranose disaccharide (β-Ara2) for the specific sugar importer. Here, we present the crystal structure of the catalytic region of HypBA2 as the first three-dimensional structure of GH121 at 1.85 Å resolution. The HypBA2 structure consists of a central catalytic (α/α)6 barrel domain and two flanking (N- and C-terminal) β-sandwich domains. A pocket in the catalytic domain appears to be suitable for accommodating the β-Ara2 disaccharide; this pocket is highly conserved among GH121 proteins. The three acidic residues Glu383, Asp515, and Glu713, located in this pocket, are completely conserved among all ~270 members of GH121; site-directed mutagenesis analysis showed that they are essential for catalytic activity. The active site of HypBA2 was compared with those of GH63 α-glycosidase, GH94 chitobiose phosphorylase, GH142 β-L-arabinofuranosidase, GH78 α-L-rhamnosidase, and GH37 α,α-trehalase. Based on these analyses, we concluded that the three conserved residues are essential for catalysis and substrate binding. β-L-Arabinobiosidase genes in GH121 are mainly found in the genomes of bifidobacteria and Xanthomonas species, suggesting that the cleavage and specific import system for the β-Ara2 disaccharide on plant hydroxyproline-rich glycoproteins are shared in animal gut symbionts and plant pathogens.

scholarly journals The PEX7-Mediated Peroxisomal Import System Is Required for Fungal Development and Pathogenicity in Magnaporthe oryzae

PLoS ONE ◽  
2011 ◽  
Vol 6 (12) ◽  
pp. e28220 ◽  
Author(s):  
Jaeduk Goh ◽  
Junhyun Jeon ◽  
Kyoung Su Kim ◽  
Jongsun Park ◽  
Sook-Young Park ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Fungal Development ◽  
Import System
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