1
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Ernst M, Orabi EA, Stockbridge RB, Faraldo-Gómez JD, Robertson JL. Dimerization mechanism of an inverted-topology ion channel in membranes. Proc Natl Acad Sci U S A 2023; 120:e2308454120. [PMID: 37956279 PMCID: PMC10666096 DOI: 10.1073/pnas.2308454120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/28/2023] [Indexed: 11/15/2023] Open
Abstract
Many ion channels are multisubunit complexes where oligomerization is an obligatory requirement for function as the binding axis forms the charged permeation pathway. However, the mechanisms of in-membrane assembly of thermodynamically stable channels are largely unknown. Here, we demonstrate a key advance by reporting the dimerization equilibrium reaction of an inverted-topology, homodimeric fluoride channel Fluc in lipid bilayers. While the wild-type channel is a long-lived dimer, we leverage a known mutation, N43S, that weakens Na+ binding in a buried site at the interface, thereby unlocking the complex for reversible association in lipid bilayers. Single-channel recordings show that Na+ binding is required for fluoride conduction while single-molecule microscopy experiments demonstrate that N43S Fluc exists in a dynamic monomer-dimer equilibrium in the membrane, even following removal of Na+. Quantifying the thermodynamic stability while titrating Na+ indicates that dimerization occurs first, providing a membrane-embedded binding site where Na+ binding weakly stabilizes the complex. To understand how these subunits form stable assemblies while presenting charged surfaces to the membrane, we carried out molecular dynamics simulations, which show the formation of a thinned membrane defect around the exposed dimerization interface. In simulations where subunits are permitted to encounter each other while preventing protein contacts, we observe spontaneous and selective association at the native interface, where stability is achieved by mitigation of the membrane defect. These results suggest a model wherein membrane-associated forces drive channel assembly in the native orientation while subsequent factors, such as Na+ binding, result in channel activation.
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Affiliation(s)
- Melanie Ernst
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110
| | - Esam A. Orabi
- Theoretical Molecular Biophysics Section, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20894
| | - Randy B. Stockbridge
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI48109
| | - José D. Faraldo-Gómez
- Theoretical Molecular Biophysics Section, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20894
| | - Janice L. Robertson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110
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2
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Badonyi M, Marsh JA. Buffering of genetic dominance by allele-specific protein complex assembly. SCIENCE ADVANCES 2023; 9:eadf9845. [PMID: 37256959 PMCID: PMC10413657 DOI: 10.1126/sciadv.adf9845] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/24/2023] [Indexed: 06/02/2023]
Abstract
Protein complex assembly often occurs while subunits are being translated, resulting in complexes whose subunits were translated from the same mRNA in an allele-specific manner. It has thus been hypothesized that such cotranslational assembly may counter the assembly-mediated dominant-negative effect, whereby co-assembly of mutant and wild-type subunits "poisons" complex activity. Here, we show that cotranslationally assembling subunits are much less likely to be associated with autosomal dominant relative to recessive disorders, and that subunits with dominant-negative disease mutations are significantly depleted in cotranslational assembly compared to those associated with loss-of-function mutations. We also find that complexes with known dominant-negative effects tend to expose their interfaces late during translation, lessening the likelihood of cotranslational assembly. Finally, by combining complex properties with other features, we trained a computational model for predicting proteins likely to be associated with non-loss-of-function disease mechanisms, which we believe will be of considerable utility for protein variant interpretation.
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Affiliation(s)
- Mihaly Badonyi
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, UK
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3
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Tao A, Liu G, Zhang R, Yuan J. Precise Measurement of the Stoichiometry of the Adaptive Bacterial Flagellar Switch. mBio 2023; 14:e0018923. [PMID: 36946730 PMCID: PMC10128058 DOI: 10.1128/mbio.00189-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023] Open
Abstract
The cytoplasmic ring (C-ring) of the bacterial flagellar motor controls the motor rotation direction, thereby controlling bacterial run-and-tumble behavior. The C-ring has been shown to undergo adaptive remodeling in response to changes in motor directional bias. However, the stoichiometry and arrangement of the C-ring is still unclear due to contradiction between the results from fluorescence studies and cryo-electron microscopy (cryo-EM) structural analysis. Here, by using the copy number of FliG molecules (34) in the C-ring as a reference, we precisely measured the copy numbers of FliM molecules in motors rotating exclusively counterclockwise (CCW) and clockwise (CW). We surprisingly found that there are on average 45 and 58 FliM molecules in CW and CCW rotating motors, respectively, which are much higher than previous estimates. Our results suggested a new mechanism of C-ring adaptation, that is, extra FliM molecules could be bound to the primary C-ring with probability depending on the motor rotational direction. We further confirmed that all of the FliM molecules in the C-ring function in chemotaxis signaling transduction because all of them could be bound by the chemotactic response regulator CheY-P. Our measurements provided new insights into the structure and arrangement of the flagellar switch. IMPORTANCE The bacterial flagellar switch can undergo adaptive remodeling in response to changes in motor rotation direction, thereby shifting its operating point to match the output of the chemotaxis signaling pathway. However, it remains unclear how the flagellar switch accomplishes this adaptive remodeling. Here, via precise fluorescence studies, we measured the absolute copy numbers of the critical component in the switch for motors rotating counterclockwise and clockwise, obtaining much larger numbers than previous relative estimates. Our results suggested a new mechanism of adaptive remodeling of the flagellar switch and provided new insights for updating the conformation spread model of the switch.
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Affiliation(s)
- Antai Tao
- Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
| | - Guangzhe Liu
- Wenzhou Institute, University of Chinese Academy of Science, Wenzhou, Zhejiang, P.R. China
- School of Engineering and Science, University of Chinese Academy of Science, Beijing, P.R. China
| | - Rongjing Zhang
- Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
| | - Junhua Yuan
- Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
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4
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Ernst M, Orabi EA, Stockbridge RB, Faraldo-Gómez JD, Robertson JL. Dimerization mechanism of an inverted-topology ion channel in membranes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.27.525942. [PMID: 36789410 PMCID: PMC9928038 DOI: 10.1101/2023.01.27.525942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Many ion channels are multi-subunit complexes with a polar permeation pathway at the oligomeric interface, but their mechanisms of assembly into functional, thermodynamically stable units within the membrane are largely unknown. Here we characterize the assembly of the inverted-topology, homodimeric fluoride channel Fluc, leveraging a known mutation, N43S, that weakens Na + binding to the dimer interface, thereby unlocking the complex. While single-channel recordings show Na + is required for activation, single-molecule photobleaching and bulk Förster Resonance Energy Transfer experiments in lipid bilayers demonstrate that N43S Fluc monomers and dimers exist in dynamic equilibrium, even without Na + . Molecular dynamics simulations indicate this equilibrium is dominated by a differential in the lipid-solvation energetics of monomer and dimer, which stems from hydrophobic exposure of the polar ion pathway in the monomer. These results suggest a model wherein membrane-associated forces induce channel assembly while subsequent factors, in this case Na + binding, result in channel activation. Teaser Membrane morphology energetics foster inverted-topology Fluc channels to form dimers, which then become active upon Na + binding.
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5
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Jacobs M, Bansal P, Shukla D, Schroeder CM. Understanding Supramolecular Assembly of Supercharged Proteins. ACS CENTRAL SCIENCE 2022; 8:1350-1361. [PMID: 36188338 PMCID: PMC9523778 DOI: 10.1021/acscentsci.2c00730] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Indexed: 06/16/2023]
Abstract
Ordered supramolecular assemblies have recently been created using electrostatic interactions between oppositely charged proteins. Despite recent progress, the fundamental mechanisms governing the assembly of oppositely supercharged proteins are not fully understood. Here, we use a combination of experiments and computational modeling to systematically study the supramolecular assembly process for a series of oppositely supercharged green fluorescent protein variants. We show that net charge is a sufficient molecular descriptor to predict the interaction fate of oppositely charged proteins under a given set of solution conditions (e.g., ionic strength), but the assembled supramolecular structures critically depend on surface charge distributions. Interestingly, our results show that a large excess of charge is necessary to nucleate assembly and that charged residues not directly involved in interprotein interactions contribute to a substantial fraction (∼30%) of the interaction energy between oppositely charged proteins via long-range electrostatic interactions. Dynamic subunit exchange experiments further show that relatively small, 16-subunit assemblies of oppositely charged proteins have kinetic lifetimes on the order of ∼10-40 min, which is governed by protein composition and solution conditions. Broadly, our results inform how protein supercharging can be used to create different ordered supramolecular assemblies from a single parent protein building block.
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Affiliation(s)
- Michael
I. Jacobs
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Prateek Bansal
- Department
of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Diwakar Shukla
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Charles M. Schroeder
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Materials Science and Engineering, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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6
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A multi-state dynamic process confers mechano-adaptation to a biological nanomachine. Nat Commun 2022; 13:5327. [PMID: 36088344 PMCID: PMC9464220 DOI: 10.1038/s41467-022-33075-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 08/26/2022] [Indexed: 11/08/2022] Open
Abstract
Adaptation is a defining feature of living systems. The bacterial flagellar motor adapts to changes in the external mechanical load by adding or removing torque-generating (stator) units. But the molecular mechanism behind this mechano-adaptation remains unclear. Here, we combine single motor eletrorotation experiments and theoretical modeling to show that mechano-adaptation of the flagellar motor is enabled by multiple mechanosensitive internal states. Dwell time statistics from experiments suggest the existence of at least two bound states with a high and a low unbinding rate, respectively. A first-passage-time analysis of a four-state model quantitatively explains the experimental data and determines the transition rates among all four states. The torque generated by bound stator units controls their effective unbinding rate by modulating the transition between the bound states, possibly via a catch bond mechanism. Similar force-mediated feedback enabled by multiple internal states may apply to adaptation in other macromolecular complexes. Combining experiments with modeling, Wadhwa et al. propose a model for mechano-adaptation in the bacterial flagellar motor, finding that load-dependent transitions between multiple internal states govern the binding and unbinding of subunits.
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7
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Brown JWP, Alford RG, Walsh JC, Spinney RE, Xu SY, Hertel S, Berengut JF, Spenkelink LM, van Oijen AM, Böcking T, Morris RG, Lee LK. Rapid Exchange of Stably Bound Protein and DNA Cargo on a DNA Origami Receptor. ACS NANO 2022; 16:6455-6467. [PMID: 35316035 DOI: 10.1021/acsnano.2c00699] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Biomolecular complexes can form stable assemblies yet can also rapidly exchange their subunits to adapt to environmental changes. Simultaneously allowing for both stability and rapid exchange expands the functional capacity of biomolecular machines and enables continuous function while navigating a complex molecular world. Inspired by biology, we design and synthesize a DNA origami receptor that exploits multivalent interactions to form stable complexes that are also capable of rapid subunit exchange. The system utilizes a mechanism first outlined in the context of the DNA replisome, known as multisite competitive exchange, and achieves a large separation of time scales between spontaneous subunit dissociation, which requires days, and rapid subunit exchange, which occurs in minutes. In addition, we use the DNA origami receptor to demonstrate stable interactions with rapid exchange of both DNA and protein subunits, thus highlighting the applicability of our approach to arbitrary molecular cargo, an important distinction with canonical toehold exchange between single-stranded DNA. We expect this study to benefit future studies that use DNA origami structures to exploit multivalent interactions for the design and synthesis of a wide range of possible kinetic behaviors.
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Affiliation(s)
- James W P Brown
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Rokiah G Alford
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - James C Walsh
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Richard E Spinney
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
- School of Physics, University of New South Wales, Sydney 2052, Australia
| | - Stephanie Y Xu
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Sophie Hertel
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Jonathan F Berengut
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
- School of Chemistry, University of Sydney, Sydney 2006, Australia
| | - Lisanne M Spenkelink
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Antoine M van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
- Illawarra Health & Medical Research Institute, Wollongong, New South Wales 2522, Australia
| | - Till Böcking
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Richard G Morris
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
- School of Physics, University of New South Wales, Sydney 2052, Australia
| | - Lawrence K Lee
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
- ARC Centre of Excellence in Synthetic Biology, University of New South Wales, Sydney 2052, Australia
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8
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Perez-Carrasco R, Franco-Oñate MJ, Walter JC, Dorignac J, Geniet F, Palmeri J, Parmeggiani A, Walliser NO, Nord AL. Relaxation time asymmetry in stator dynamics of the bacterial flagellar motor. SCIENCE ADVANCES 2022; 8:eabl8112. [PMID: 35319986 PMCID: PMC8942351 DOI: 10.1126/sciadv.abl8112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The bacterial flagellar motor is the membrane-embedded rotary motor, which turns the flagellum that provides thrust to many bacteria. This large multimeric complex, composed of a few dozen constituent proteins, is a hallmark of dynamic subunit exchange. The stator units are inner-membrane ion channels that dynamically bind to the peptidoglycan at the rotor periphery and apply torque. Their dynamic exchange is a function of the viscous load on the flagellum, allowing the bacterium to adapt to its local environment, although the molecular mechanisms of mechanosensitivity remain unknown. Here, by actively perturbing the steady-state stator stoichiometry of individual motors, we reveal a stoichiometry-dependent asymmetry in stator remodeling kinetics. We interrogate the potential effect of next-neighbor interactions and local stator unit depletion and find that neither can explain the observed asymmetry. We then simulate and fit two mechanistically diverse models that recapitulate the asymmetry, finding assembly dynamics to be particularly well described by a two-state catch-bond mechanism.
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Affiliation(s)
| | | | - Jean-Charles Walter
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Jérôme Dorignac
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Fred Geniet
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - John Palmeri
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Andrea Parmeggiani
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Nils-Ole Walliser
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Ashley L Nord
- Centre de Biologie Structurale, Univ. Montpellier, CNRS, INSERM, Montpellier, France
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9
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Sahtoe DD, Praetorius F, Courbet A, Hsia Y, Wicky BI, Edman NI, Miller LM, Timmermans BJR, Decarreau J, Morris HM, Kang A, Bera AK, Baker D. Reconfigurable asymmetric protein assemblies through implicit negative design. Science 2022; 375:eabj7662. [PMID: 35050655 PMCID: PMC9881579 DOI: 10.1126/science.abj7662] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Asymmetric multiprotein complexes that undergo subunit exchange play central roles in biology but present a challenge for design because the components must not only contain interfaces that enable reversible association but also be stable and well behaved in isolation. We use implicit negative design to generate β sheet-mediated heterodimers that can be assembled into a wide variety of complexes. The designs are stable, folded, and soluble in isolation and rapidly assemble upon mixing, and crystal structures are close to the computational models. We construct linearly arranged hetero-oligomers with up to six different components, branched hetero-oligomers, closed C4-symmetric two-component rings, and hetero-oligomers assembled on a cyclic homo-oligomeric central hub and demonstrate that such complexes can readily reconfigure through subunit exchange. Our approach provides a general route to designing asymmetric reconfigurable protein systems.
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Affiliation(s)
- Danny D. Sahtoe
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195,HHMI, University of Washington, Seattle, WA 98195
| | - Florian Praetorius
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Alexis Courbet
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195,HHMI, University of Washington, Seattle, WA 98195
| | - Yang Hsia
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Basile I.M. Wicky
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Natasha I. Edman
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195,Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA, USA.,Medical Scientist Training Program, University of Washington, Seattle, WA, USA
| | - Lauren M. Miller
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Bart J. R. Timmermans
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Justin Decarreau
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Hana M. Morris
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Alex Kang
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - Asim K. Bera
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA 98195,Institute for Protein Design, University of Washington, Seattle, WA 98195,HHMI, University of Washington, Seattle, WA 98195,Corresponding author.
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10
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Lin TS, Kojima S, Fukuoka H, Ishijima A, Homma M, Lo CJ. Stator Dynamics Depending on Sodium Concentration in Sodium-Driven Bacterial Flagellar Motors. Front Microbiol 2021; 12:765739. [PMID: 34899649 PMCID: PMC8661058 DOI: 10.3389/fmicb.2021.765739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 10/19/2021] [Indexed: 11/17/2022] Open
Abstract
Bacterial flagellar motor (BFM) is a large membrane-spanning molecular rotary machine for swimming motility. Torque is generated by the interaction between the rotor and multiple stator units powered by ion-motive force (IMF). The number of bound stator units is dynamically changed in response to the external load and the IMF. However, the detailed dynamics of stator unit exchange process remains unclear. Here, we directly measured the speed changes of sodium-driven chimeric BFMs under fast perfusion of different sodium concentration conditions using computer-controlled, high-throughput microfluidic devices. We found the sodium-driven chimeric BFMs maintained constant speed over a wide range of sodium concentrations by adjusting stator units in compensation to the sodium-motive force (SMF) changes. The BFM has the maximum number of stator units and is most stable at 5 mM sodium concentration rather than higher sodium concentration. Upon rapid exchange from high to low sodium concentration, the number of functional stator units shows a rapidly excessive reduction and then resurrection that is different from predictions of simple absorption model. This may imply the existence of a metastable hidden state of the stator unit during the sudden loss of sodium ions.
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Affiliation(s)
- Tsai-Shun Lin
- Department of Physics and Center for Complex Systems, National Central University, Taoyuan City, Taiwan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Hajime Fukuoka
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Akihiko Ishijima
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Chien-Jung Lo
- Department of Physics and Center for Complex Systems, National Central University, Taoyuan City, Taiwan
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11
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Abstract
Bacteria have developed a large array of motility mechanisms to exploit available resources and environments. These mechanisms can be broadly classified into swimming in aqueous media and movement over solid surfaces. Swimming motility involves either the rotation of rigid helical filaments through the external medium or gyration of the cell body in response to the rotation of internal filaments. On surfaces, bacteria swarm collectively in a thin layer of fluid powered by the rotation of rigid helical filaments, they twitch by assembling and disassembling type IV pili, they glide by driving adhesins along tracks fixed to the cell surface and, finally, non-motile cells slide over surfaces in response to outward forces due to colony growth. Recent technological advances, especially in cryo-electron microscopy, have greatly improved our knowledge of the molecular machinery that powers the various forms of bacterial motility. In this Review, we describe the current understanding of the physical and molecular mechanisms that allow bacteria to move around.
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12
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Wimmi S, Balinovic A, Jeckel H, Selinger L, Lampaki D, Eisemann E, Meuskens I, Linke D, Drescher K, Endesfelder U, Diepold A. Dynamic relocalization of cytosolic type III secretion system components prevents premature protein secretion at low external pH. Nat Commun 2021; 12:1625. [PMID: 33712575 PMCID: PMC7954860 DOI: 10.1038/s41467-021-21863-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 02/12/2021] [Indexed: 01/31/2023] Open
Abstract
Many bacterial pathogens use a type III secretion system (T3SS) to manipulate host cells. Protein secretion by the T3SS injectisome is activated upon contact to any host cell, and it has been unclear how premature secretion is prevented during infection. Here we report that in the gastrointestinal pathogens Yersinia enterocolitica and Shigella flexneri, cytosolic injectisome components are temporarily released from the proximal interface of the injectisome at low external pH, preventing protein secretion in acidic environments, such as the stomach. We show that in Yersinia enterocolitica, low external pH is detected in the periplasm and leads to a partial dissociation of the inner membrane injectisome component SctD, which in turn causes the dissociation of the cytosolic T3SS components. This effect is reversed upon restoration of neutral pH, allowing a fast activation of the T3SS at the native target regions within the host. These findings indicate that the cytosolic components form an adaptive regulatory interface, which regulates T3SS activity in response to environmental conditions.
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Affiliation(s)
- Stephan Wimmi
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Alexander Balinovic
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Department of Physics, Mellon College of Science, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Hannah Jeckel
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Lisa Selinger
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Dimitrios Lampaki
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Max-Planck-Institut für Immunbiologie und Epigenetik, Freiburg, Germany
| | - Emma Eisemann
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- James Madison University, Harrisonburg, VA, USA
| | - Ina Meuskens
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Dirk Linke
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Knut Drescher
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Ulrike Endesfelder
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Department of Physics, Mellon College of Science, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
- SYNMIKRO, LOEWE Center for Synthetic Microbiology, Marburg, Germany.
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13
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Milne-Davies B, Wimmi S, Diepold A. Adaptivity and dynamics in type III secretion systems. Mol Microbiol 2020; 115:395-411. [PMID: 33251695 DOI: 10.1111/mmi.14658] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/17/2020] [Accepted: 11/23/2020] [Indexed: 01/07/2023]
Abstract
The type III secretion system is the common core of two bacterial molecular machines: the flagellum and the injectisome. The flagellum is the most widely distributed prokaryotic locomotion device, whereas the injectisome is a syringe-like apparatus for inter-kingdom protein translocation, which is essential for virulence in important human pathogens. The successful concept of the type III secretion system has been modified for different bacterial needs. It can be adapted to changing conditions, and was found to be a dynamic complex constantly exchanging components. In this review, we highlight the flexibility, adaptivity, and dynamic nature of the type III secretion system.
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Affiliation(s)
- Bailey Milne-Davies
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Stephan Wimmi
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
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14
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Abstract
The bacterial flagellar motor is the most complex structure in the bacterial cell, driving the ion-driven rotation of the helical flagellum. The ordered expression of the regulon and the assembly of the series of interacting protein rings, spanning the inner and outer membranes to form the ∼45–50-nm protein complex, have made investigation of the structure and mechanism a major challenge since its recognition as a rotating nanomachine about 40 years ago. Painstaking molecular genetics, biochemistry, and electron microscopy revealed a tiny electric motor spinning in the bacterial membrane. Over the last decade, new single-molecule and in vivo biophysical methods have allowed investigation of the stability of this and other large protein complexes, working in their natural environment inside live cells. This has revealed that in the bacterial flagellar motor, protein molecules in both the rotor and stator exchange with freely circulating pools of spares on a timescale of minutes, even while motors are continuously rotating. This constant exchange has allowed the evolution of modified components allowing bacteria to keep swimming as the viscosity or the ion composition of the outside environment changes.
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Affiliation(s)
- Judith P. Armitage
- Department of Biochemistry, University of Oxford, OX1 3QU, United Kingdom
| | - Richard M. Berry
- Department of Physics, University of Oxford, OX1 3PU, United Kingdom
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15
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Nord AL, Pedaci F. Mechanisms and Dynamics of the Bacterial Flagellar Motor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1267:81-100. [PMID: 32894478 DOI: 10.1007/978-3-030-46886-6_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Many bacteria are able to actively propel themselves through their complex environment, in search of resources and suitable niches. The source of this propulsion is the Bacterial Flagellar Motor (BFM), a molecular complex embedded in the bacterial membrane which rotates a flagellum. In this chapter we review the known physical mechanisms at work in the motor. The BFM shows a highly dynamic behavior in its power output, its structure, and in the stoichiometry of its components. Changes in speed, rotation direction, constituent protein conformations, and the number of constituent subunits are dynamically controlled in accordance to external chemical and mechanical cues. The mechano-sensitivity of the motor is likely related to the surface-sensing ability of bacteria, relevant in the initial stage of biofilm formation.
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Affiliation(s)
- A L Nord
- Centre de Biochimie Structurale (CBS), INSERM, CNRS, University of Montpellier, Montpellier, France
| | - F Pedaci
- Centre de Biochimie Structurale (CBS), INSERM, CNRS, University of Montpellier, Montpellier, France.
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Thangaraj SK, James S, Rouvinen J, Jänis J. Thermokinetic Analysis of Protein Subunit Exchange by Variable-Temperature Native Mass Spectrometry. Biochemistry 2019; 58:5025-5029. [PMID: 31790206 DOI: 10.1021/acs.biochem.9b00911] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many protein complexes are assembled from a varying number of subunits, which are continuously exchanging with diverse time scales. This structural dynamics is considered to be important for many regulatory and sensory adaptation processes that occur in vivo. We have developed an accurate method for monitoring protein subunit exchange by using native electrospray ionization mass spectrometry (ESI-MS), exemplified here for an extremely stable Rad50 zinc hook (Hk) dimer assembly, Zn(Hk)2. The method has two steps: appropriate protein/peptide mutation and native ESI-MS analysis using a variable-temperature sample inlet. In this work, two Hk mutants were produced, mixed with wild-type Hk, and measured at three different temperatures. A thermokinetic analysis of heterodimer formation allowed us to determine the enthalpy, entropy, and Gibbs free energy of activation for subunit exchange, showing that the reaction is slow and associated with a high enthalpic barrier, consistent with the exceptionally high stability of the Zn(Hk)2 assembly.
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Affiliation(s)
- Senthil K Thangaraj
- Department of Chemistry , University of Eastern Finland , P.O. Box 111, FI-801101 Joensuu , Finland
| | - Salman James
- Department of Chemistry , University of Eastern Finland , P.O. Box 111, FI-801101 Joensuu , Finland
| | - Juha Rouvinen
- Department of Chemistry , University of Eastern Finland , P.O. Box 111, FI-801101 Joensuu , Finland
| | - Janne Jänis
- Department of Chemistry , University of Eastern Finland , P.O. Box 111, FI-801101 Joensuu , Finland
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17
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Abstract
Multisubunit protein complexes are ubiquitous in biology and perform a plethora of essential functions. Most of the scientific literature treats such assemblies as static: their function is assumed to be independent of their manner of assembly, and their structure is assumed to remain intact until they are degraded. Recent observations of the bacterial flagellar motor, among others, bring these notions into question. The torque-generating stator units of the motor assemble and disassemble in response to changes in load. Here, we used electrorotation to drive tethered cells forward, which decreases motor load, and measured the resulting stator dynamics. No disassembly occurred while the torque remained high, but all of the stator units were released when the motor was spun near the zero-torque speed. When the electrorotation was turned off, so that the load was again high, stator units were recruited, increasing motor speed in a stepwise fashion. A model in which speed affects the binding rate and torque affects the free energy of bound stator units captures the observed torque-dependent stator assembly dynamics, providing a quantitative framework for the environmentally regulated self-assembly of a major macromolecular machine.
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Diepold A. Assembly and Post-assembly Turnover and Dynamics in the Type III Secretion System. Curr Top Microbiol Immunol 2019; 427:35-66. [PMID: 31218503 DOI: 10.1007/82_2019_164] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type III secretion system (T3SS) is one of the largest transmembrane complexes in bacteria, comprising several intricately linked and embedded substructures. The assembly of this nanomachine is a hierarchical process which is regulated and controlled by internal and external cues at several critical points. Recently, it has become obvious that the assembly of the T3SS is not a unidirectional and deterministic process, but that parts of the T3SS constantly exchange or rearrange. This article aims to give an overview on the assembly and post-assembly dynamics of the T3SS, with a focus on emerging general concepts and adaptations of the general assembly pathway.
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Affiliation(s)
- Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Straße 10, 35043, Marburg, Germany.
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van Oijen AM, Duderstadt KE, Xiao J, Fishel R. Plasticity of Multi-Protein Complexes. J Mol Biol 2018; 430:4441-4442. [PMID: 30102893 DOI: 10.1016/j.jmb.2018.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Antoine M van Oijen
- School of Chemistry, University of Wollongong, Northfields Avenue, Wollongong, NSW 2500, Australia.
| | - Karl E Duderstadt
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
| | - Richard Fishel
- College of Medicine, The Ohio State University, 460 W. 12th Ave., Columbus, OH 43210, USA
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