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Protein unfolding and translocation

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https://www.readbyqxmd.com/read/28421184/the-proteasomal-atpases-use-a-slow-but-highly-processive-strategy-to-unfold-proteins
#1
Aaron Snoberger, Raymond T Anderson, David M Smith
All domains of life have ATP-dependent compartmentalized proteases that sequester their peptidase sites on their interior. ATPase complexes will often associate with these compartmentalized proteases in order to unfold and inject substrates into the protease for degradation. Significant effort has been put into understanding how ATP hydrolysis is used to apply force to proteins and cause them to unfold. The unfolding kinetics of the bacterial ATPase, ClpX, have been shown to resemble a fast motor that traps unfolded intermediates as a strategy to unfold proteins...
2017: Frontiers in Molecular Biosciences
https://www.readbyqxmd.com/read/28419599/mycobacterium-tuberculosis-proteasomal-atpase-mpa-has-a-%C3%AE-grasp-domain-that-hinders-docking-with-the-proteasome-core-protease
#2
Yujie Wu, Kuan Hu, Defeng Li, Lin Bai, Shaoqing Yang, Jordan B Jastrab, Shuhao Xiao, Yonglin Hu, Susan Zhang, K Heran Darwin, Tao Wang, Huilin Li
Mycobacterium tuberculosis (Mtb) has a proteasome system that is essential for its ability to cause lethal infections in mice. A key component of the system is the proteasomal adenosine triphosphatase (ATPase) Mpa, which captures, unfolds, and translocates protein substrates into the Mtb proteasome core particle for degradation. Here, we report the crystal structures of near full-length hexameric Mtb Mpa in apo and ADP-bound forms. Surprisingly, the structures revealed a ubiquitin-like β-grasp domain that precedes the proteasome-activating carboxyl terminus...
April 17, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28417122/frequency-control-of-protein-translocation-across-an-oscillating-nanopore
#3
Fabio Cecconi, Muhammad Adnan Shahzad, Umberto Marini Bettolo Marconi, Angelo Vulpiani
The translocation of a lipid binding protein (LBP) is studied using a phenomenological coarse-grained computational model that simplifies both chain and pore geometry. We investigated via molecular dynamics the interplay between transport and unfolding in the presence of a nanopore whose section oscillates periodically in time with a frequency ω, a motion often referred to as the radial breathing mode (RBM). We found that the LPB when mechanically pulled into the vibrating nanopore exhibits a translocation dynamics that in some frequency range is accelerated and shows a frequency locking to the pore dynamics...
April 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28407373/activation-of-the-arabidopsis-membrane-bound-transcription-factor-bzip28-is-mediated-by-site-2-protease-but-not-site-1-protease
#4
Yuji Iwata, Makoto Ashida, Chisa Hasegawa, Kazuki Tabara, Kei-Ichiro Mishiba, Nozomu Koizumi
The unfolded protein response (UPR) is a homeostatic cellular response conserved in eukaryotic cells to alleviate the accumulation of unfolded proteins in the endoplasmic reticulum (ER). Arabidopsis bZIP28 is a membrane-bound transcription factor activated by proteolytic cleavage in response to ER stress, thereby releasing its cytosolic portion containing the bZIP domain from the membrane to translocate into the nucleus where it induces the transcription of genes encoding ER-resident molecular chaperones and folding enzymes...
April 13, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28397859/an-optimized-transit-peptide-for-effective-targeting-of-diverse-foreign-proteins-into-chloroplasts-in-rice
#5
Bo-Ran Shen, Cheng-Hua Zhu, Zhen Yao, Li-Li Cui, Jian-Jun Zhang, Cheng-Wei Yang, Zheng-Hui He, Xin-Xiang Peng
Various chloroplast transit peptides (CTP) have been used to successfully target some foreign proteins into chloroplasts, but for other proteins these same CTPs have reduced localization efficiencies or fail completely. The underlying cause of the failures remains an open question, and more effective CTPs are needed. In this study, we initially observed that two E.coli enzymes, EcTSR and EcGCL, failed to be targeted into rice chloroplasts by the commonly-used rice rbcS transit peptide (rCTP) and were subsequently degraded...
April 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28389941/fuel-of-the-bacterial-flagellar-type-iii-protein-export-apparatus
#6
Tohru Minamino, Miki Kinoshita, Keiichi Namba
The flagellar type III export apparatus utilizes ATP and proton motive force (PMF) across the cytoplasmic membrane as the energy sources and transports flagellar component proteins from the cytoplasm to the distal growing end of the growing structure to construct the bacterial flagellum beyond the cellular membranes. The flagellar type III export apparatus coordinates flagellar protein export with assembly by ordered export of substrates to parallel with their order of the assembly. The export apparatus is composed of a PMF-driven transmembrane export gate complex and a cytoplasmic ATPase complex...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28286085/hspa5-gene-encoding-hsp70-chaperone-bip-in-the-endoplasmic-reticulum
#7
REVIEW
Jie Wang, Jessica Lee, David Liem, Peipei Ping
The HSPA5 gene (Ensembl ID: ENSG00000044574 (WTSI/EMBL-EBI, 2015)) encodes the binding immunoglobulin protein (BiP), an Hsp70 family chaperone localized in the ER lumen. As a highly conserved molecular chaperone, BiP assists in a wide range of folding processes via its two structural domains, a nucleotide-binding domain (NBD) and substrate-binding domain (SBD). BiP is also an essential component of the translocation machinery for protein import into the ER, a regulator for Ca(2+) homeostasis in the ER, as well as a facilitator of ER-associated protein degradation (ERAD) via retrograde transportation of aberrant proteins across the ER membrane...
March 7, 2017: Gene
https://www.readbyqxmd.com/read/28237106/methods-to-study-chaperone-mediated-autophagy
#8
E Arias
Chaperone-mediated autophagy (CMA), a selective form of degradation of cytosolic proteins in lysosomes, contributes to maintenance of proteostasis and to the cellular adaptation to stress. CMA substrates are selectively recognized and delivered by a cytosolic chaperone to the lysosomal surface, where, upon unfolding, they are internalized through a membrane translocation complex. Defective or dysfunctional CMA has been associated with human pathologies such as neurodegeneration, cancer, immunodeficiency, or diabetes, increasing the overall interest in methods to monitor this selective autophagic pathway...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28223361/covalently-linked-hslu-hexamers-support-a-probabilistic-mechanism-that-links-atp-hydrolysis-to-protein-unfolding-and-translocation
#9
Vladimir Baytshtok, Jiejin Chen, Steven E Glynn, Andrew R Nager, Robert A Grant, Tania A Baker, Robert T Sauer
The HslUV proteolytic machine consists of HslV, a double-ring self-compartmentalized peptidase, and one or two AAA+ HslU ring hexamers that hydrolyze ATP to power the unfolding of protein substrates and their translocation into the proteolytic chamber of HslV. Here, we use genetic tethering and disulfide bonding strategies to construct HslU pseudohexamers containing mixtures of ATPase active and inactive subunits at defined positions in the hexameric ring. Genetic tethering impairs HslV binding and degradation, even for pseudohexamers with six active subunits, but disulfide-linked pseudohexamers do not have these defects, indicating that the peptide tether interferes with HslV interactions...
April 7, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28216041/structure-of-a-type-1-secretion-system-abc-transporter
#10
Jacob L W Morgan, Justin F Acheson, Jochen Zimmer
Type-1 secretion systems (T1SSs) represent a widespread mode of protein secretion across the cell envelope in Gram-negative bacteria. The T1SS is composed of an inner-membrane ABC transporter, a periplasmic membrane-fusion protein, and an outer-membrane porin. These three components assemble into a complex spanning both membranes and providing a conduit for the translocation of unfolded polypeptides. We show that ATP hydrolysis and assembly of the entire T1SS complex is necessary for protein secretion. Furthermore, we present a 3...
March 7, 2017: Structure
https://www.readbyqxmd.com/read/28115689/structural-insights-into-the-functional-cycle-of-the-atpase-module-of-the-26s-proteasome
#11
Marc Wehmer, Till Rudack, Florian Beck, Antje Aufderheide, Günter Pfeifer, Jürgen M Plitzko, Friedrich Förster, Klaus Schulten, Wolfgang Baumeister, Eri Sakata
In eukaryotic cells, the ubiquitin-proteasome system (UPS) is responsible for the regulated degradation of intracellular proteins. The 26S holocomplex comprises the core particle (CP), where proteolysis takes place, and one or two regulatory particles (RPs). The base of the RP is formed by a heterohexameric AAA(+) ATPase module, which unfolds and translocates substrates into the CP. Applying single-particle cryo-electron microscopy (cryo-EM) and image classification to samples in the presence of different nucleotides and nucleotide analogs, we were able to observe four distinct conformational states (s1 to s4)...
February 7, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28115202/secondary-structure-preferences-of-the-anthrax-toxin-protective-antigen-translocase
#12
Debasis Das, Bryan A Krantz
In order for many proteins to move across hydrophobic membrane bilayers, they must be unfolded and translocated by a membrane-embedded channel. These translocase channels interact with the substrate proteins they translocate via hydrophobic pore loops and cleft structures called clamps. The molecular basis for how clamps facilitate unfolding and translocation is poorly understood. Anthrax toxin is composed of three proteins, a translocase channel-forming subunit, called protective antigen (PA), and two substrate proteins, called lethal factor (LF) and edema factor...
March 10, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28069863/ubiquitin-recognition-by-the-proteasome
#13
Yasushi Saeki
The 26S proteasome is a 2.5-MDa complex responsible for the selective, ATP-dependent degradation of ubiquitylated proteins in eukaryotic cells. Substrates in hundreds cellular pathways are timely ubiquitylated and converged to the proteasome by direct recognition or by multiple shuttle factors. Engagement of substrate protein triggers conformational changes of the proteasome, which drive substrate unfolding, deubiquitylation and translocation of substrates to proteolytic sites. Recent studies have challenged the previous paradigm that Lys48-linked tetraubiquitin is a minimal degradation signal: in addition, monoubiquitylation or multiple short ubiquitylations can serve as the targeting signal for proteasomal degradation...
February 1, 2017: Journal of Biochemistry
https://www.readbyqxmd.com/read/28067475/the-chaperonin-tric-forms-an-oligomeric-complex-in-the-malaria-parasite-cytosol
#14
Natalie J Spillman, Josh R Beck, Suresh M Ganesan, Jacquin C Niles, Daniel E Goldberg
The malaria parasite exports numerous proteins into its host red blood cell (RBC). The trafficking of these exported effectors is complex. Proteins are first routed through the secretory system, into the parasitophorous vacuole (PV), a membranous compartment enclosing the parasite. Proteins are then translocated across the PV membrane in a process requiring ATP and unfolding. Once in the RBC compartment the exported proteins are then refolded and further trafficked to their final localizations. Chaperones are important in the unfolding and refolding processes...
January 9, 2017: Cellular Microbiology
https://www.readbyqxmd.com/read/28032645/arabidopsis-b-cell-lymphoma2-bcl-2-associated-athanogene-7-bag7-mediated-heat-tolerance-requires-translocation-sumoylation-and-binding-to-wrky29
#15
Yurong Li, Brett Williams, Martin Dickman
To cope with stress and increased accumulation of misfolded proteins, plants and animals use a survival pathway known as the unfolded protein response (UPR) that signals between the endoplasmic reticulum (ER) and the nucleus to maintain cell homeostasis via proper folding of proteins. B-cell lymphoma2 (Bcl-2)-associated athanogene (BAG) proteins are an evolutionarily conserved family of co-chaperones that are linked to disease states in mammals and responses to environmental stimuli (biotic and abiotic) in plants...
December 29, 2016: New Phytologist
https://www.readbyqxmd.com/read/28010734/proteins-adopt-functionally-active-conformations-after-type-iii-secretion
#16
Kevin James Metcalf, James Lea Bevington, Sandy Lisette Rosales, Lisa Ann Burdette, Elias Valdivia, Danielle Tullman-Ercek
BACKGROUND: Bacterial production of natively folded heterologous proteins by secretion to the extracellular space can improve protein production by simplifying purification and enabling continuous processing. In a typical bacterial protein production process, the protein of interest accumulates in the cytoplasm of the cell, requiring cellular lysis and extensive purification to separate the desired protein from other cellular constituents. The type III secretion system of Gram-negative bacteria is used to secrete proteins from the cytosol to the extracellular space in one step, but proteins must unfold during translocation, necessitating the folding of secreted proteins in the extracellular space for an efficient production process...
December 23, 2016: Microbial Cell Factories
https://www.readbyqxmd.com/read/27981232/strain-dependent-recognition-of-a-unique-degradation-motif-by-clpxp-in-streptococcus-mutans
#17
Biswanath Jana, Liang Tao, Indranil Biswas
Streptococcus mutans, a dental pathogen, has a remarkable ability to cope with environmental stresses. Under stress conditions, cytoplasmic proteases play a major role in controlling the stability of regulatory proteins and preventing accumulation of damaged and misfolded proteins. ClpXP, a well-conserved cytoplasmic proteolytic system, is crucial in maintaining cellular homeostasis in bacteria. ClpX is primarily responsible for recognition of substrates and subsequent translocation of unfolded substrates into the ClpP proteolytic compartment for degradation...
November 2016: MSphere
https://www.readbyqxmd.com/read/27960258/mechanism-of-the-spontaneous-and-directional-membrane-insertion-of-a-2-transmembrane-ion-channel
#18
Steffen Altrichter, Maximilian Haase, Belinda Loh, Andreas Kuhn, Sebastian Leptihn
Protein insertion into membranes is a process occurring in every cell and every cellular compartment. Yet, many thermodynamic aspects of this fundamental biophysical process are not well understood. We investigated physicochemical parameters that influence protein insertion using the model protein KcsA, a 2-transmembrane ion channel. To understand what drives insertion and to identify individual steps of protein integration into a highly apolar environment, we investigated the contribution of electrostatic interactions and lipid composition on protein insertion on a single molecule level...
December 21, 2016: ACS Chemical Biology
https://www.readbyqxmd.com/read/27864322/escherichia-coli-proteome-microarrays-identified-the-substrates-of-clpyq-protease
#19
Chih-Hsuan Tsai, Yu-Hsuan Ho, Tzu-Cheng Sung, Whei-Fen Wu, Chien-Sheng Chen
Proteolysis is a vital mechanism to regulate the cellular proteome in all kingdoms of life, and ATP-dependent proteases play a crucial role within this process. In Escherichia coli, ClpYQ is one of the primary ATP-dependent proteases. In addition to function with removals of abnormal peptides in the cells, ClpYQ degrades regulatory proteins if necessary and thus let cells adjust to various environmental conditions. In E. coli, SulA, RcsA, RpoH and TraJ as well as RNase R, have been identified as natural protein substrates of ClpYQ...
January 2017: Molecular & Cellular Proteomics: MCP
https://www.readbyqxmd.com/read/27844434/mechanically-watching-the-clpxp-proteolytic-machinery
#20
Juan Carlos Cordova, Adrian O Olivares, Matthew J Lang
Energy-dependent protein degradation is studied through the dual bead ClpXP motility assay. Processing of folded proteins involves recognition, unfolding, translocation, and degradation stages. A dual optical trap, in a passive force-clamp geometry, exhibits bead-to-bead displacements that directly follow subprocesses underlying protein degradation. Discrete nanometer-scale displacements of the bead position reveal steps, dwells and pauses during the unfolding and translocation substeps. With a few structural modifications to the protease machinery and an engineered substrate, the assay represents a "chassis" for the measurement of a wide range of substrates and related machinery...
2017: Methods in Molecular Biology
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