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https://www.readbyqxmd.com/read/28439563/mechanism-of-vps4-hexamer-function-revealed-by-cryo-em
#1
Min Su, Emily Z Guo, Xinqiang Ding, Yan Li, Jeffrey T Tarrasch, Charles L Brooks, Zhaohui Xu, Georgios Skiniotis
Vps4 is a member of AAA(+) ATPase (adenosine triphosphatase associated with diverse cellular activities) that operates as an oligomer to disassemble ESCRT-III (endosomal sorting complex required for transport III) filaments, thereby catalyzing the final step in multiple ESCRT-dependent membrane remodeling events. We used electron cryo-microscopy to visualize oligomers of a hydrolysis-deficient Vps4 (vacuolar protein sorting-associated protein 4) mutant in the presence of adenosine 5'-triphosphate (ATP). We show that Vps4 subunits assemble into an asymmetric hexameric ring following an approximate helical path that sequentially stacks substrate-binding loops along the central pore...
April 2017: Science Advances
https://www.readbyqxmd.com/read/28416111/structural-analysis-reveals-features-of-ribosome-assembly-factor-nsa1-wdr74-important-for-localization-and-interaction-with-rix7-nvl2
#2
Yu-Hua Lo, Erin M Romes, Monica C Pillon, Mack Sobhany, Robin E Stanley
Ribosome assembly is a complex process that requires hundreds of essential assembly factors, including Rix7 (NVL2 in mammals) and Nsa1 (WDR74 in mammals). Rix7 is a type II double ring, AAA-ATPase, which is closely related to the well-known Cdc48/p97. Previous studies in Saccharomyces cerevisiae suggest that Rix7 mediates the release of Nsa1 from nucleolar pre-60S particles; however, the underlying mechanisms of this release are unknown. Through multiple structural analyses we show that S. cerevisiae Nsa1 is composed of an N-terminal seven-bladed WD40 domain followed by a lysine-rich C terminus that extends away from the WD40 domain and is required for nucleolar localization...
April 12, 2017: Structure
https://www.readbyqxmd.com/read/28400297/characterization-of-ecca3-a-cbbx-family-atpase-from-the-esx-3-secretion-pathway-of-m-tuberculosis
#3
Amit Gaur, Vijay Kumar Sharma, Sonal Shree, Niyati Rai, Ravishankar Ramachandran
EccA family proteins are conserved components of ESX secretion pathways in M. tuberculosis H37Rv. Here, we report the characterization of EccA3 (Rv0282), a CbbX family AAA (ATPases Associated with diverse cellular Activities) protein from the ESX-3 pathway that is required for in vitro growth of mycobacteria, secretion of virulence factors, and acquisition of iron and zinc. EccA3 is a thermostable ATPase with a molecular weight of ~68kDa. It exists as a dodecamer in the apo form and associates as a hexamer in the presence of ATP...
April 8, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28389272/characterization-of-ciliobrevin-a-mediated-dynein-atpase-inhibition-on-flagellar-motility-of-leishmania-donovani
#4
G Srinivas Reddy, Aakash Gautam Mukhopadhyay, Chinmoy Sankar Dey
Axonemal dyneins are members of AAA+ proteins involved in force generation and are responsible for flagellar motility in eukaryotes. In this study, we characterized the effects of ciliobrevin A (CbA), a dynein ATPase inhibitor, on flagella driven motility of the protozoan parasite Leishmania donovani. Using fast-capture video microscopy, we observed that CbA decreased flagellar beat frequency of swimming parasites in a concentration-dependent manner. Beat frequency of live and reactivated L. donovani decreased by approximately 89% and 41% respectively in the presence of 250μM CbA...
April 5, 2017: Molecular and Biochemical Parasitology
https://www.readbyqxmd.com/read/28379137/structural-basis-of-protein-translocation-by-the-vps4-vta1-aaa-atpase
#5
Nicole Monroe, Han Han, Peter S Shen, Wesley I Sundquist, Christopher P Hill
Many important cellular membrane fission reactions are driven by ESCRT pathways, which culminate in disassembly of ESCRT-III polymers by the AAA ATPase Vps4. We report a 4.3 Å resolution cryo-EM structure of the active Vps4 hexamer with its cofactor Vta1, ADP•BeFx, and an ESCRT-III substrate peptide. Four Vps4 subunits form a helix whose interfaces are consistent with ATP-binding, is stabilized by Vta1, and binds the substrate peptide. The fifth subunit approximately continues this helix but appears to be dissociating...
April 5, 2017: ELife
https://www.readbyqxmd.com/read/28352916/a-threonine-turnstile-defines-a-dynamic-amphiphilic-binding-motif-in-the-aaa-atpase-p97-allosteric-binding-site
#6
James C Burnett, Chaemin Lim, Brian D Peyser, Lalith P Samankumara, Marina Kovaliov, Raffaele Colombo, Stacie L Bulfer, Matthew G LaPorte, Ann R Hermone, Connor F McGrath, Michelle R Arkin, Rick Gussio, Donna M Huryn, Peter Wipf
The turnstile motion of two neighboring threonines sets up a dynamic side chain interplay that can accommodate both polar and apolar ligands in a small molecule allosteric protein binding site. A computational model based on SAR data and both X-ray and cryo-EM structures of the AAA ATPase p97 was used to analyze the effects of paired threonines at the inhibitor site. Specifically, the Thr side chain hydroxyl groups form a hydrogen bonding network that readily accommodates small, highly polar ligand substituents...
March 29, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28318378/pexophagy-is-responsible-for-65-of-cases-of-peroxisome-biogenesis-disorders
#7
Taras Y Nazarko
Peroxisome biogenesis disorders (PBDs) is a group of diseases caused by mutations in one of the peroxins, proteins responsible for biogenesis of the peroxisomes. In recent years, it became clear that many peroxins (e.g., PEX3 and PEX14) play additional roles in peroxisome homeostasis (such as promoting autophagic degradation of peroxisomes or pexophagy), which are often opposite to their originally established functions in peroxisome formation and maintenance. Even more interesting, the peroxins that make up the peroxisomal AAA ATPase complex (AAA-complex) in yeast (Pex1, Pex6 and Pex15) or mammals (PEX1, PEX6, PEX26) are responsible for the downregulation of pexophagy...
February 28, 2017: Autophagy
https://www.readbyqxmd.com/read/28303975/a-conserved-inter-domain-communication-mechanism-regulates-the-atpase-activity-of-the-aaa-protein-drg1
#8
Michael Prattes, Mathias Loibl, Gertrude Zisser, Daniel Luschnig, Lisa Kappel, Ingrid Rössler, Manuela Grassegger, Altijana Hromic, Elmar Krieger, Karl Gruber, Brigitte Pertschy, Helmut Bergler
AAA-ATPases fulfil essential roles in different cellular pathways and often act in form of hexameric complexes. Interaction with pathway-specific substrate and adaptor proteins recruits them to their targets and modulates their catalytic activity. This substrate dependent regulation of ATP hydrolysis in the AAA-domains is mediated by a non-catalytic N-terminal domain. The exact mechanisms that transmit the signal from the N-domain and coordinate the individual AAA-domains in the hexameric complex are still the topic of intensive research...
March 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28287898/consequences-of-a-tight-squeeze-nuclear-envelope-rupture-and-repair
#9
Philipp Isermann, Jan Lammerding
Cell migration through tight spaces can induce substantial deformations of the nucleus and cause nuclear envelope (NE) rupture, resulting in uncontrolled exchange of nuclear and cytosolic proteins. These events can cause DNA damage and, in severe cases, nuclear fragmentation, challenging the integrity of the genomic material. Cells overcome NE ruptures during interphase by repairing the NE using components of the endosomal sorting complexes required for transport (ESCRT) machinery. Paralleling the molecular mechanism employed during NE reformation in late mitosis, ESCRT-III subunits and the associated AAA-ATPase VPS4B are recruited to NE rupture sites and help restore NE integrity...
March 13, 2017: Nucleus
https://www.readbyqxmd.com/read/28275610/mutant-analysis-reveals-allosteric-regulation-of-clpb-disaggregase
#10
Kamila B Franke, Bernd Bukau, Axel Mogk
The members of the hexameric AAA+ disaggregase of E. coli and S. cerevisiae, ClpB, and Hsp104, cooperate with the Hsp70 chaperone system in the solubilization of aggregated proteins. Aggregate solubilization relies on a substrate threading activity of ClpB/Hsp104 fueled by ATP hydrolysis in both ATPase rings (AAA-1, AAA-2). ClpB/Hsp104 ATPase activity is controlled by the M-domains, which associate to the AAA-1 ring to downregulate ATP hydrolysis. Keeping M-domains displaced from the AAA-1 ring by association with Hsp70 increases ATPase activity due to enhanced communication between protomers...
2017: Frontiers in Molecular Biosciences
https://www.readbyqxmd.com/read/28242746/torsina-regulates-the-linc-to-moving-nuclei
#11
Daniel A Starr, Lesilee S Rose
How LINC complexes are regulated to connect nuclei to the cytoskeleton during nuclear migration is unknown. Saunders et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201507113) show that the AAA+ ATPase torsinA and its partner LAP1 are required for nuclear migration during fibroblast polarization by mediating the dynamics of LINC complexes.
March 6, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/28242745/torsina-controls-tan-line-assembly-and-the-retrograde-flow-of-dorsal-perinuclear-actin-cables-during-rearward-nuclear-movement
#12
Cosmo A Saunders, Nathan J Harris, Patrick T Willey, Brian M Woolums, Yuexia Wang, Alex J McQuown, Amy Schoenhofen, Howard J Worman, William T Dauer, Gregg G Gundersen, G W Gant Luxton
The nucleus is positioned toward the rear of most migratory cells. In fibroblasts and myoblasts polarizing for migration, retrograde actin flow moves the nucleus rearward, resulting in the orientation of the centrosome in the direction of migration. In this study, we report that the nuclear envelope-localized AAA+ (ATPase associated with various cellular activities) torsinA (TA) and its activator, the inner nuclear membrane protein lamina-associated polypeptide 1 (LAP1), are required for rearward nuclear movement during centrosome orientation in migrating fibroblasts...
March 6, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/28223493/crystal-structure-of-aquifex-aeolicus-%C3%AF-n-bound-to-promoter-dna-and-the-structure-of-%C3%AF-n-holoenzyme
#13
Elizabeth A Campbell, Shreya Kamath, Kanagalaghatta R Rajashankar, Mengyu Wu, Seth A Darst
The bacterial σ factors confer promoter specificity to the RNA polymerase (RNAP). One alternative σ factor, σ(N), is unique in its structure and functional mechanism, forming transcriptionally inactive promoter complexes that require activation by specialized AAA(+) ATPases. We report a 3.4-Å resolution X-ray crystal structure of a σ(N) fragment in complex with its cognate promoter DNA, revealing the molecular details of promoter recognition by σ(N) The structure allowed us to build and refine an improved σ(N)-holoenzyme model based on previously published 3...
March 7, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28223361/covalently-linked-hslu-hexamers-support-a-probabilistic-mechanism-that-links-atp-hydrolysis-to-protein-unfolding-and-translocation
#14
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/28205175/membrane-extraction-of-hmg-coa-reductase-as-determined-by-susceptibility-of-lumenal-epitope-to-in-vitro-protease-digestion
#15
Lindsey L Morris, Russell A DeBose-Boyd
Although many aspects of the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway have been elucidated, methods to detect and examine intermediate steps in the process are lacking. Here, we describe the use of a protease protection assay to study the metabolically regulated ERAD substrate HMG CoA reductase. Studies utilizing this assay reveal that ubiquitinated reductase becomes extracted across the ER membrane prior to its cytosolic release and proteasomal degradation through reactions mediated by distinct AAA-ATPases...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28188183/variants-of-the-sir4-coiled-coil-domain-improve-binding-to-sir3-for-heterochromatin-formation-in-saccharomyces-cerevisiae
#16
Anke Samel, Adam Rudner, Ann E Ehrenhofer-Murray
Heterochromatin formation in the yeast Saccharomyces cerevisiae is characterized by the assembly of the Silent Information Regulator (SIR) complex, which consists of the histone deacetylase Sir2 and the structural components Sir3 and Sir4, and binds to unmodified nucleosomes to provide gene silencing. Sir3 contains an AAA(+) ATPase-like domain, and mutations in an exposed loop on the surface of this domain abrogate Sir3 silencing function in vivo, as well in vitro binding to the Sir2/Sir4 subcomplex. Here, we found that the removal of a single methyl group in the C-terminal coiled-coil domain (mutation T1314S) of Sir4 was sufficient to restore silencing at the silent mating-type loci HMR and HML to a Sir3 version with a mutation in this loop...
April 3, 2017: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/28157697/trip13-impairs-mitotic-checkpoint-surveillance-and-is-associated-with-poor-prognosis-in-multiple-myeloma
#17
Yi Tao, Guang Yang, Hongxing Yang, Dongliang Song, Liangning Hu, Bingqian Xie, Houcai Wang, Lu Gao, Minjie Gao, Hongwei Xu, Zhijian Xu, Xiaosong Wu, Yiwen Zhang, Weiliang Zhu, Fenghuang Zhan, Jumei Shi
AAA-ATPase TRIP13 is one of the chromosome instability gene recently established in multiple myeloma (MM), the second most common and incurable hematological malignancy. However, the specific function of TRIP13 in MM is largely unknown. Using sequential gene expression profiling, we demonstrated that high TRIP13 expression levels were positively correlated with progression, disease relapse, and poor prognosis in MM patients. Overexpressing human TRIP13 in myeloma cells prompted cell growth and drug resistance, and overexpressing murine TRIP13, which shares 93% sequence identity with human TRIP13, led to colony formation of NIH/3T3 fibroblasts in vitro and tumor formation in vivo...
February 1, 2017: Oncotarget
https://www.readbyqxmd.com/read/28118071/the-role-of-wrnip1-in-genome-maintenance
#18
Akari Yoshimura, Masayuki Seki, Takemi Enomoto
WRNIP1 interacts with WRN helicase, which is defective in the premature aging disease Werner syndrome. WRNIP1 belongs to the AAA+ ATPase family and is conserved from Escherichia coli to human. The protein contains an ubiquitin-binding zinc finger (UBZ) domain at the N terminus and an ATPase domain in the middle region. In addition to WRN, WRNIP1 interacts with proteins involved in multiple cellular pathways, including RAD18, monoubiquitylated PCNA, DNA polymerase δ, RAD51, and ATMIN. Mgs1, the yeast homolog of WRNIP1, may act downstream of ubiquitylation of PCNA to mobilize DNA polymerase δ...
March 19, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28115689/structural-insights-into-the-functional-cycle-of-the-atpase-module-of-the-26s-proteasome
#19
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/28112645/structure-of-the-active-form-of-human-origin-recognition-complex-and-its-atpase-motor-module
#20
Ante Tocilj, Kin Fan On, Zuanning Yuan, Jingchuan Sun, Elad Elkayam, Huilin Li, Bruce Stillman, Leemor Joshua-Tor
Binding of the Origin Recognition Complex (ORC) to origins of replication marks the first step in the initiation of replication of the genome in all eukaryotic cells. Here, we report the structure of the active form of human ORC determined by X-ray crystallography and cryo-electron microscopy. The complex is composed of an ORC1/4/5 motor module lobe in an organization reminiscent of the DNA polymerase clamp loader complexes. A second lobe contains the ORC2/3 subunits. The complex is organized as a double-layered shallow corkscrew, with the AAA+ and AAA+-like domains forming one layer, and the winged-helix domains (WHDs) forming a top layer...
January 23, 2017: ELife
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