The Experts below are selected from a list of 384 Experts worldwide ranked by ideXlab platform
Wolfgang Baumeister - One of the best experts on this subject based on the ideXlab platform.
-
proteomics analysis of thermoplasma acidophilum with a focus on protein complexes
Molecular & Cellular Proteomics, 2007Co-Authors: Na Sun, Wolfgang Baumeister, Frank Siedler, Florian Beck, Roland Wilhelm Knispel, Beatrix Scheffer, Stephan Nickell, Istvan NagyAbstract:Two-dimensional gel electrophoresis (2DE) and MALDI-TOF MS were used to obtain a global view of the cytoplasmic proteins expressed by Thermoplasma acidophilum. In addition, glycerol gradient ultracentrifugation coupled to 2DE-MALDI-TOF MS analysis was used to identify subunits of macromolecular complexes. With the 2DE proteomics approach, over 900 spots were resolved of which 271 proteins were identified. A significant number of these form macromolecular complexes, among them the ribosome, proteasome, and Thermosome, which are expressed at high levels. In the glycerol gradient heavy fractions, 10 as yet uncharacterized proteins (besides the well known ribosomal subunits, translation initiation factor eIF-6-related protein, elongation factor 1, and DNA-dependent RNA polymerase) were identified that are putative building blocks of protein complexes. These proteins belong to the categories of hypothetical or conserved hypothetical proteins, and they are present in the cytosol at low concentrations. Although these proteins exhibit homology to known sequences, their structures, subunit compositions, and biological functions are not yet known.
-
nmr studies on the substrate binding domains of the Thermosome structural plasticity in the protrusion region
Journal of Molecular Biology, 2004Co-Authors: Markus Heller, Wolfgang Baumeister, Michael John, Murray Coles, Gundula Bosch, Horst KesslerAbstract:Group II chaperonins close their cavity with the help of conserved, helical extensions, the so-called protrusions, which emanate from the apical or substrate-binding domains. A comparison of previously solved crystal structures of the apical domains of the Thermosome from Thermoplasma acidophilum showed structural plasticity in the protrusion parts induced by extensive packing interactions. In order to assess the influence of the crystal contacts we investigated both the alpha and beta-apical domains (alpha-ADT and beta-ADT) in solution by NMR spectroscopy. Secondary structure assignments and 15N backbone relaxation measurements showed mostly rigid structural elements in the globular parts of the domains, but revealed intrinsic structural disorder and partial helix fraying in the protrusion regions. On the other hand, a beta-turn-motif conserved in archaeal group II chaperonins might facilitate substrate recognition. Our results help us to specify the idea of the open, substrate-accepting state of the Thermosome and may provide an additional jigsaw piece in understanding the mode of substrate binding of group II chaperonins.
-
atp induced structural change of the Thermosome is temperature dependent
Journal of Structural Biology, 2001Co-Authors: Irina Gutsche, Wolfgang Baumeister, Jorg Holzinger, Nadine R Rauh, R P MayAbstract:Protein folding by chaperonins is powered by ATP binding and hydrolysis. ATPase activity drives the folding machine through a series of conformational rearrangements, extensively described for the group I chaperonin GroEL from Escherichia coli but still poorly understood for the group II chaperonins. The latter--archaeal Thermosome and eukaryotic TRiC/CCT--function independently of a GroES-like cochaperonin and are proposed to rely on protrusions of their own apical domains for opening and closure in an ATP-controlled fashion. Here we use small-angle neutron scattering to analyze structural changes of the recombinant alpha-only and the native alphabeta-Thermosome from Thermoplasma acidophilum upon their ATPase cycling in solution. We show that specific high-salt conditions, but not the presence of MgATP alone, induce formation of higher order Thermosome aggregates. The mechanism of the open-closed transition of the Thermosome is strongly temperature-dependent. ATP binding to the chaperonin appears to be a two-step process: at lower temperatures an open state of the ATP-Thermosome is predominant, whereas heating to physiological temperatures induces its switching to a closed state. Our data reveal an analogy between the ATPase cycles of the two groups of chaperonins and enable us to put forward a model of Thermosome action.
-
toward detecting and identifying macromolecules in a cellular context template matching applied to electron tomograms
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Jochen Bohm, Stephan Nickell, Achilleas S Frangakis, Reiner Hegerl, Dieter Typke, Wolfgang BaumeisterAbstract:Electron tomography is the only technique available that allows us to visualize the three-dimensional structure of unfixed and unstained cells currently with a resolution of 6–8 nm, but with the prospect to reach 2–4 nm. This raises the possibility of detecting and identifying specific macromolecular complexes within their cellular context by virtue of their structural signature. Templates derived from the high-resolution structure of the molecule under scrutiny are used to search the reconstructed volume. Here we outline and test a computationally feasible two-step procedure: In a first step, mean-curvature motion is used for segmentation, yielding subvolumes that contain with a high probability macromolecules in the expected size range. Subsequently, the particles contained in the subvolumes are identified by cross-correlation, using a set of three-dimensional templates. With simulated and real tomographic data we demonstrate that such an approach is feasible and we explore the detection limits. Even structurally similar particles, such as the Thermosome, GroEL, and the 20S proteasome can be identified with high fidelity. This opens up exciting prospects for mapping the territorial distribution of macromolecules and for analyzing molecular interactions in situ.
-
crystal structure of the beta apical domain of the Thermosome reveals structural plasticity in the protrusion region
Journal of Molecular Biology, 2000Co-Authors: Gundula Bosch, Wolfgang Baumeister, Larsoliver EssenAbstract:Abstract The crystal structure of the β-apical domain of the Thermosome, an archaeal group II chaperonin from Thermoplasma acidophilum , has been determined at 2.8 A resolution. The structure shows an invariant globular core from which a 25 A long protrusion emanates, composed of an elongated α-helix (H10) and a long extended stretch consisting of residues GluB245-ThrB253. A comparison with previous apical domain structures reveals a large segmental displacement of the protruding part of helix H10 via the hinge GluB276-ValB278. The region comprising residues GluB245-ThrB253 adopts an extended β-like conformation rather than the α-helix seen in the α-apical domain. Consequently, it appears that the protrusions of the apical domains from group II chaperonins might assume a variety of context-dependent conformations during an open, substrate-accepting state of the chaperonin. Sequence variations in the protrusion regions that are found in the eukaryotic TRiC/CCT subunits may provide different structural propensities and hence serve different roles in substrate recognition.
Baumeister W. - One of the best experts on this subject based on the ideXlab platform.
-
ATP-induced structural change of the Thermosome is temperature-dependent
2001Co-Authors: Holzinger J., Baumeister W., Rauh N., May R. P.Abstract:Protein folding by chaperonins is powered by ATP binding and hydrolysis. ATPase activity drives the folding machine through a series of conformational rearrangements, extensively described for the group I chaperonin GroEL from Escherichia coli but still poorly understood for the group II chaperonins. The latter-archaeal Thermosome and eukaryotic TMUCCT-function independently of a GroES-like cochaperonin and are proposed to rely on protrusions of their own apical domains for opening and closure in an ATP-controlled fashion. Here we use small-angle neutron scattering to analyze structural changes of the recombinant a-only and the native alpha beta -Thermosome from Thermoplasma acidophilum upon their ATPase cycling in solution. We show that specific high-salt conditions, but not the presence of MgATP alone, induce formation of higher order Thermosome aggregates. The mechanism of the open-closed transition of the Thermosome is strongly temperature-dependent. ATP binding to the chaperonin appears to be a two-step process: at lower temperatures an open state of the ATP-Thermosome is predominant, whereas heating to physiological temperatures induces its switching to a closed state. Our data reveal an analogy between the ATPase cycles of the two groups of chaperonins and enable us to put forward a model of Thermosome action. (C) 2001 Academic Press. [References: 24
-
J. Struct. Biol
2001Co-Authors: Holzinger J., Baumeister W., Rauh N., May R.Abstract:Protein folding by chaperonins is powered by ATP binding and hydrolysis. ATPase activity drives the folding machine through a series of conformational rearrangements, extensively described for the group I chaperonin GroEL from Escherichia coli but still poorly understood for the group II chaperonins. The latter-archaeal Thermosome and eukaryotic TMUCCT-function independently of a GroES-like cochaperonin and are proposed to rely on protrusions of their own apical domains for opening and closure in an ATP-controlled fashion. Here we use small-angle neutron scattering to analyze structural changes of the recombinant a-only and the native alpha beta -Thermosome from Thermoplasma acidophilum upon their ATPase cycling in solution. We show that specific high-salt conditions, but not the presence of MgATP alone, induce formation of higher order Thermosome aggregates. The mechanism of the open-closed transition of the Thermosome is strongly temperature-dependent. ATP binding to the chaperonin appears to be a two-step process: at lower temperatures an open state of the ATP-Thermosome is predominant, whereas heating to physiological temperatures induces its switching to a closed state. Our data reveal an analogy between the ATPase cycles of the two groups of chaperonins and enable us to put forward a model of Thermosome action. (C) 2001 Academic Press. [References: 24
-
Toward detecting and identifying macromolecules in a cellular context: Template matching applied to electron tomograms
2000Co-Authors: Böhm J., Typke D., Hegerl R., Frangakis A. S., Nickell S., Baumeister W.Abstract:Electron tomography is the only technique available that allows us to visualize the three-dimensional structure of unfixed and unstained cells currently with a resolution of 6-8 nm, but with the prospect to reach 2-4 nm. This raises the possibility of detecting and identifying specific macromolecular complexes within their cellular context by Virtue of their structural signature. Templates derived from the high-resolution structure of the molecule under scrutiny are used to search the reconstructed volume. Here we outline and test a computationally feasible two-step procedure: In a first step, mean-curvature motion is used for segmentation, yielding subvolumes that contain with a high probability macromolecules in the expected size range. Subsequently, the particles contained in the subvolumes are identified by cross-correlation, using a set of three-dimensional templates. With simulated and real tomographic data we demonstrate that such an approach is feasible and we explore the detection limits. Even structurally similar particles, such as the Thermosome, GroEL, and the 20S proteasome can be identified with high fidelity. This opens up exciting prospects for mapping the territorial distribution of macromolecules and for analyzing molecular interactions in situ. [References: 31
-
FEBS Lett
2000Co-Authors: Mihalache O., Typke D., Hegerl R., Baumeister W.Abstract:Chaperonins are double-ring protein folding machines fueled by ATP binding and hydrolysis. Conformational rearrangements upon ATPase cycling of the group I chaperonins, typified by the Escherichia coli GroEL/GroES system, have been thoroughly investigated by cryo-electron microscopy and X-ray crystallography. For archaeal group II chaperonins, however, these methods have so far failed to provide a correlation between the structural and the functional states. Here, we show that the conformation of the native alpha beta-Thermosome of Thermoplasma acidophilum in vitrified ice is strictly regulated by adenine nucleotides. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved. [References: 18
-
ATPase cycle of an archaeal chaperonin
2000Co-Authors: Mihalache O., Baumeister W.Abstract:Recent structural data imply differences in allosteric behavior of the group I chaperonins, typified by GroEL from Escherichia coli, and the group II chaperonins, which comprise archaeal Thermosome and eukaryotic TRiC/CCT. Therefore, this study addresses the mechanism of interaction of adenine nucleotides with recombinant alpha-only and native alpha beta-Thermosomes from Thermoplasma acidophilum acidophilum, which also enables us to analyze the role of the heterooligomeric composition of the natural Thermosome. Although all subunits of the alpha-only Thermosome seem to bind nucleotides tightly and independently, the native chaperonin has two different classes of ATP-binding sites. Furthermore, for the alpha-only Thermosome, the steady-state ATPase rate is determined by the cleavage reaction itself, whereas, for the alpha beta-Thermosome, the rate-limiting step is associated with a post-hydrolysis isomerisation into a non-covalent ADP*P-i species prior to the release of the gamma-phosphate group. After half-saturation with ATP, a negative cooperativity in hydrolysis is observed for both Thermosomes. The effect of Mg2+ and K+ nucleotide cycling is documented. We conclude that archaeal chaperonins have unique allosteric properties and discuss them in the light of the mechanism established for the group I chaperonins. (C) 2000 Academic Press. [References: 52
Nico Bruns - One of the best experts on this subject based on the ideXlab platform.
-
using the dendritic polymer pamam to form gold nanoparticles in the protein cage Thermosome
Chemical Communications, 2016Co-Authors: Martin G Nussbaumer, Christoph Bisig, Nico BrunsAbstract:The chaperonin Thermosome (THS) is a protein cage that lacks binding sites for metal ions and inorganic nanoparticles. However, when poly(amidoamine) (PAMAM) is encapsulated into THS, gold nanoparticles (AuNP) can be prepared in the THS. The polymer binds HAuCl4. Subsequent reduction yields nanoparticles with narrow size distribution in the protein-polymer conjugate.
-
A chaperonin as protein nanoreactor for atom-transfer radical polymerization.
Angewandte Chemie International Edition, 2013Co-Authors: Kasper Renggli, Martin G Nussbaumer, Raphael Urbani, Thomas Pfohl, Nico BrunsAbstract:The group II chaperonin Thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom-transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N-isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein–catalyst conjugate only yielded polymers with PDIs above 1.84.
-
self reporting materials protein mediated visual indication of damage in a bulk polymer
Chimia, 2011Co-Authors: Nico Bruns, Douglas S. ClarkAbstract:Damage self-reporting materials are able to indicate the presence of microscopic damaged regions by easy to detect signals, such as fluorescence. Therefore, these smart materials can reduce the risk of catastrophic failure of load-bearing components, e.g., in aerospace and construction applications. We highlight here our proof-of-concept paper and we present some additional data, which shows that proteins can be used as mechanophores in solid polymeric materials. Macroscopic mechanical forces were transferred from the polymer to the embedded proteins. The biomolecules act as molecular strain sensor, giving the material the desired self-reporting property. Poly(ethylene glycol) and poly(acrylamide) (PAAm) networks were doped with small amounts of thermsosome (THS), a protein cage from the family of chaperonins, that encapsulated a pair of fluorescent proteins. THS acts as a scaffold which brings the two fluorescent proteins into distance suitable for fluorescence resonance energy transfer (FRET). Moreover, THS can be distorted by mechanic forces so that the distance between the fluorescent proteins changes, leading to a change in FRET efficiency. Using the brittle PAAm as a model system, we were able to visualize microcracks in the polymers by FRET microscopy and by fluorescence lifetime imaging. THS also stabilizes the encapsulated guest proteins against thermal denaturation, increasing their half-live at 70 degrees C by a factor of 2.3.
-
mechanical nanosensor based on fret within a Thermosome damage reporting polymeric materials
Angewandte Chemie, 2009Co-Authors: Lisa M Bergeron, Nico Bruns, Katarzyna Pustelny, Timothy A Whitehead, Douglas S. ClarkAbstract:Unter Spannung: Andert sich in einem Protein-Polymer-Hybridmaterial die mechanische Spannung der Polymermatrix, so lost dies eine Konformationsanderung des Proteinkomplexes aus: Das Material meldet eine strukturelle Schadigung (siehe Bild). Die Reporterkomponente ist ein Chaperonin, das ein Paar fluoreszierender Proteine kovalent bindet. Wird das Chaperonin deformiert, andert sich der Abstand zwischen den Fluorophoren und folglich auch das FRET-Signal. Under stress: Changes in stress of the polymer matrix in a protein-polymer hybrid material result in changes of conformation of the protein complex, thus resulting in a damage-reporting material (see picture). The reporter is an engineered chaperonin that covalently entraps a pair of fluorescent proteins. Deformation of the chaperonin leads to a change in fluorophore distance and a change in the fluorescene resonance energy transfer (FRET) signal.
-
inside cover mechanical nanosensor based on fret within a Thermosome damage reporting polymeric materials angew chem int ed 31 2009
Angewandte Chemie, 2009Co-Authors: Lisa M Bergeron, Nico Bruns, Katarzyna Pustelny, Timothy A Whitehead, Douglas S. ClarkAbstract:An engineered hybrid protein assembly that is embedded in a polymer acts as a sensor for structural deformation of the matrix. In their Communication on D. S. Clark and co-workers report the encapsulation of a FRET pair of fluorescent proteins into a chaperonin. The protein hybrid was copolymerized with a monomer to produce a self-reporting material. Damage is reported by a change in the fluorescence signal when the material is mechanically stressed.
Larsoliver Essen - One of the best experts on this subject based on the ideXlab platform.
-
crystal structure of the beta apical domain of the Thermosome reveals structural plasticity in the protrusion region
Journal of Molecular Biology, 2000Co-Authors: Gundula Bosch, Wolfgang Baumeister, Larsoliver EssenAbstract:Abstract The crystal structure of the β-apical domain of the Thermosome, an archaeal group II chaperonin from Thermoplasma acidophilum , has been determined at 2.8 A resolution. The structure shows an invariant globular core from which a 25 A long protrusion emanates, composed of an elongated α-helix (H10) and a long extended stretch consisting of residues GluB245-ThrB253. A comparison with previous apical domain structures reveals a large segmental displacement of the protruding part of helix H10 via the hinge GluB276-ValB278. The region comprising residues GluB245-ThrB253 adopts an extended β-like conformation rather than the α-helix seen in the α-apical domain. Consequently, it appears that the protrusions of the apical domains from group II chaperonins might assume a variety of context-dependent conformations during an open, substrate-accepting state of the chaperonin. Sequence variations in the protrusion regions that are found in the eukaryotic TRiC/CCT subunits may provide different structural propensities and hence serve different roles in substrate recognition.
-
crystal structure of the beta apical domain of the Thermosome reveals structural plasticity in the protrusion region
Journal of Molecular Biology, 2000Co-Authors: Gundula Bosch, Wolfgang Baumeister, Larsoliver EssenAbstract:The crystal structure of the beta-apical domain of the Thermosome, an archaeal group II chaperonin from Thermoplasma acidophilum, has been determined at 2.8 A resolution. The structure shows an invariant globular core from which a 25 A long protrusion emanates, composed of an elongated alpha-helix (H10) and a long extended stretch consisting of residues GluB245-ThrB253. A comparison with previous apical domain structures reveals a large segmental displacement of the protruding part of helix H10 via the hinge GluB276-ValB278. The region comprising residues GluB245-ThrB253 adopts an extended beta-like conformation rather than the alpha-helix seen in the alpha-apical domain. Consequently, it appears that the protrusions of the apical domains from group II chaperonins might assume a variety of context-dependent conformations during an open, substrate-accepting state of the chaperonin. Sequence variations in the protrusion regions that are found in the eukaryotic TRiC/CCT subunits may provide different structural propensities and hence serve different roles in substrate recognition.
-
group ii chaperonins new tric k s and turns of a protein folding machine
Journal of Molecular Biology, 1999Co-Authors: Irina Gutsche, Larsoliver Essen, Wolfgang BaumeisterAbstract:In the past decade, the eubacterial group I chaperonin GroEL became the paradigm of a protein folding machine. More recently, electron microscopy and X-ray crystallography offered insights into the structure of the Thermosome, the archetype of the group II chaperonins which also comprise the chaperonin from the eukaryotic cytosol TRiC. Some structural differences from GroEL were revealed, namely the existence of a built-in lid provided by the helical protrusions of the apical domains instead of a GroES-like co-chaperonin. These structural studies provide a framework for understanding the differences in the mode of action between the group II and the group I chaperonins. In vitro analyses of the folding of non-native substrates coupled to ATP binding and hydrolysis are progressing towards establishing a functional cycle for group II chaperonins. A protein complex called GimC/prefoldin has recently been found to cooperate with TRiC in vivo, and its characterization is under way.
-
structure of the substrate binding domain of the Thermosome an archaeal group ii chaperonin
Cell, 1997Co-Authors: Martin Klumpp, Wolfgang Baumeister, Larsoliver EssenAbstract:The crystal structure of the substrate binding domain of the Thermosome, the archaeal group II chaperonin, has been determined at 2.3 A resolution. The core resembles the apical domain of GroEL but lacks the hydrophobic residues implied in binding of substrates to group I chaperonins. Rather, a large hydrophobic surface patch is found in a novel helix-turn-helix motif, which is characteristic of all group II chaperonins including the eukaryotic TRiC/CCT complex. Models of the holochaperonin, which are consistent with cryo electron microscopy data, suggest a dual role of this helical protrusion in substrate binding and controlling access to the central cavity independent of a GroES-like cochaperonin.
Ulrich F Hartl - One of the best experts on this subject based on the ideXlab platform.
-
differential substrate specificity of group i and group ii chaperonins in the archaeon methanosarcina mazei
Molecular Microbiology, 2009Co-Authors: Angela Hirtreiter, Giulia Calloni, Francesca Forner, Burghardt Scheibe, Magda Puype, Joel Vandekerckhove, Matthias Mann, Ulrich F HartlAbstract:: Chaperonins are macromolecular machines that assist in protein folding. The archaeon Methanosarcina mazei has acquired numerous bacterial genes by horizontal gene transfer. As a result, both the bacterial group I chaperonin, GroEL, and the archaeal group II chaperonin, Thermosome, coexist. A proteome-wide analysis of chaperonin interactors was performed to determine the differential substrate specificity of GroEL and Thermosome. At least 13% of soluble M. mazei proteins interact with chaperonins, with the two systems having partially overlapping substrate sets. Remarkably, chaperonin selectivity is independent of phylogenetic origin and is determined by distinct structural and biochemical features of proteins. GroEL prefers well-conserved proteins with complex alpha/beta domains. In contrast, Thermosome substrates comprise a group of faster-evolving proteins and contain a much wider range of different domain folds, including small all-alpha and all-beta modules, and a greater number of large multidomain proteins. Thus, the group II chaperonins may have facilitated the evolution of the highly complex proteomes characteristic of eukaryotic cells.
-
SIGNIFICANCE OF SUBSTRATE ENCAPSULATION*
2009Co-Authors: Luis Figueiredo, Daniel Klunker, Dean J Naylor, Ulrich F Hartl, Costa Georgopoulos, Debbie Ang, Michael J. Kerner, Manajit Hayer-hartlAbstract:In all three kingdoms of life chaperonins assist the folding of a range of newly synthesized proteins. As shown recently, Archaea of the genus Methanosarcina contain both group I (GroEL/GroES) and group II (Thermosome) chaperonins in the cytosol. Here we report on a detailed functional analysis of the archaeal GroEL/ GroES system of Methanosarcina mazei (Mm) in comparison to its bacterial counterpart from Escherichia coli (Ec). We find that the groESgroEL operon of M. mazei is unable to functionally replace groESgroEL in E. coli. However, the MmGroES protein can largely complement a mutant EcGroES protein in vivo. The ATPase rate of MmGroEL is very low and the dissociation of MmGroES from MmGroEL is 15 times slower than for the EcGroEL/ GroES system. This slow ATPase cycle results in a prolonge
-
functional characterization of an archaeal groel groes chaperonin system significance of substrate encapsulation
Journal of Biological Chemistry, 2004Co-Authors: Luis Figueiredo, Daniel Klunker, Dean J Naylor, Ulrich F Hartl, Costa Georgopoulos, Debbie Ang, Michael J. Kerner, Manajit HayerhartlAbstract:Abstract In all three kingdoms of life chaperonins assist the folding of a range of newly synthesized proteins. As shown recently, Archaea of the genus Methanosarcina contain both group I (GroEL/GroES) and group II (Thermosome) chaperonins in the cytosol. Here we report on a detailed functional analysis of the archaeal GroEL/GroES system of Methanosarcina mazei (Mm) in comparison to its bacterial counterpart from Escherichia coli (Ec). We find that the groESgroEL operon of M. mazei is unable to functionally replace groESgroEL in E. coli. However, the MmGroES protein can largely complement a mutant EcGroES protein in vivo. The ATPase rate of MmGroEL is very low and the dissociation of MmGroES from MmGroEL is 15 times slower than for the EcGroEL/GroES system. This slow ATPase cycle results in a prolonged enclosure time for model substrate proteins, such as rhodanese, in the MmGroEL:GroES folding cage before their release into the medium. Interestingly, optimal functionality of MmGroEL/GroES and its ability to encapsulate larger proteins, such as malate dehydrogenase, requires the presence of ammonium sulfate in vitro. In the absence of ammonium sulfate, malate dehydrogenase fails to be encapsulated by GroES and rather cycles on and off the GroEL trans ring in a non-productive reaction. These results indicate that the archaeal GroEL/GroES system has preserved the basic encapsulation mechanism of bacterial GroEL and suggest that it has adjusted the length of its reaction cycle to the slower growth rates of Archaea. Additionally, the release of only the folded protein from the GroEL/GroES cage may prevent adverse interactions of the GroEL substrates with the Thermosome, which is not normally located within the same compartment.
-
coexistence of group i and group ii chaperonins in the archaeon methanosarcina mazei
Journal of Biological Chemistry, 2003Co-Authors: Daniel Klunker, Uwe Deppenmeier, Angela Hirtreiter, Luis Figueiredo, Dean J Naylor, Gunter Pfeifer, Volker Muller, Bernd Haas, Gerhard Gottschalk, Ulrich F HartlAbstract:Abstract Two distantly related classes of cylindrical chaperonin complexes assist in the folding of newly synthesized and stress-denatured proteins in an ATP-dependent manner. Group I chaperonins are thought to be restricted to the cytosol of bacteria and to mitochondria and chloroplasts, whereas the group II chaperonins are found in the archaeal and eukaryotic cytosol. Here we show that members of the archaeal genus Methanosarcina co-express both the complete group I (GroEL/GroES) and group II (Thermosome/prefoldin) chaperonin systems in their cytosol. These mesophilic archaea have acquired between 20 and 35% of their genes by lateral gene transfer from bacteria. In Methanosarcina mazei Go1, both chaperonins are similarly abundant and are moderately induced under heat stress. The M. mazei GroEL/GroES proteins have the structural features of their bacterial counterparts. The Thermosome contains three paralogous subunits, α, β, and γ, which assemble preferentially at a molar ratio of 2:1:1. As shown in vitro, the assembly reaction is dependent on ATP/Mg2+ or ADP/Mg2+ and the regulatory role of the β subunit. The co-existence of both chaperonin systems in the same cellular compartment suggests the Methanosarcina species as useful model systems in studying the differential substrate specificity of the group I and II chaperonins and in elucidating how newly synthesized proteins are sorted from the ribosome to the proper chaperonin for folding.
-
coexistence of group i and group ii chaperonins in the archaeon methanosarcina mazei
Journal of Biological Chemistry, 2003Co-Authors: Daniel Klunker, Uwe Deppenmeier, Angela Hirtreiter, Luis Figueiredo, Dean J Naylor, Gunter Pfeifer, Volker Muller, Bernd Haas, Gerhard Gottschalk, Ulrich F HartlAbstract:Two distantly related classes of cylindrical chaperonin complexes assist in the folding of newly synthesized and stress-denatured proteins in an ATP-dependent manner. Group I chaperonins are thought to be restricted to the cytosol of bacteria and to mitochondria and chloroplasts, whereas the group II chaperonins are found in the archaeal and eukaryotic cytosol. Here we show that members of the archaeal genus Methanosarcina co-express both the complete group I (GroEL/GroES) and group II (Thermosome/prefoldin) chaperonin systems in their cytosol. These mesophilic archaea have acquired between 20 and 35% of their genes by lateral gene transfer from bacteria. In Methanosarcina mazei Go1, both chaperonins are similarly abundant and are moderately induced under heat stress. The M. mazei GroEL/GroES proteins have the structural features of their bacterial counterparts. The Thermosome contains three paralogous subunits, alpha, beta, and gamma, which assemble preferentially at a molar ratio of 2:1:1. As shown in vitro, the assembly reaction is dependent on ATP/Mg2+ or ADP/Mg2+ and the regulatory role of the beta subunit. The co-existence of both chaperonin systems in the same cellular compartment suggests the Methanosarcina species as useful model systems in studying the differential substrate specificity of the group I and II chaperonins and in elucidating how newly synthesized proteins are sorted from the ribosome to the proper chaperonin for folding.
