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Dersch S, Reimold C, Stoll J, Breddermann H, Heimerl T, Defeu Soufo HJ, Graumann PL. Polymerization of Bacillus subtilis MreB on a lipid membrane reveals lateral co-polymerization of MreB paralogs and strong effects of cations on filament formation. BMC Mol Cell Biol 2020; 21:76. [PMID: 33148162 PMCID: PMC7641798 DOI: 10.1186/s12860-020-00319-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 10/18/2020] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND MreB is a bacterial ortholog of actin and forms mobile filaments underneath the cell membrane, perpendicular to the long axis of the cell, which play a crucial role for cell shape maintenance. We wished to visualize Bacillus subtilis MreB in vitro and therefore established a protocol to obtain monomeric protein, which could be polymerized on a planar membrane system, or associated with large membrane vesicles. RESULTS Using a planar membrane system and electron microscopy, we show that Bacillus subtilis MreB forms bundles of filaments, which can branch and fuse, with an average width of 70 nm. Fluorescence microscopy of non-polymerized YFP-MreB, CFP-Mbl and mCherry-MreBH proteins showed uniform binding to the membrane, suggesting that 2D diffusion along the membrane could facilitate filament formation. After addition of divalent magnesium and calcium ions, all three proteins formed highly disordered sheets of filaments that could split up or merge, such that at high protein concentration, MreB and its paralogs generated a network of filaments extending away from the membrane. Filament formation was positively affected by divalent ions and negatively by monovalent ions. YFP-MreB or CFP-Mbl also formed filaments between two adjacent membranes, which frequently has a curved appearance. New MreB, Mbl or MreBH monomers could add to the lateral side of preexisting filaments, and MreB paralogs co-polymerized, indicating direct lateral interaction between MreB paralogs. CONCLUSIONS Our data show that B. subtilis MreB paralogs do not easily form ordered filaments in vitro, possibly due to extensive lateral contacts, but can co-polymerise. Monomeric MreB, Mbl and MreBH uniformly bind to a membrane, and form irregular and frequently split up filamentous structures, facilitated by the addition of divalent ions, and counteracted by monovalent ions, suggesting that intracellular potassium levels may be one important factor to counteract extensive filament formation and filament splitting in vivo.
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Affiliation(s)
- Simon Dersch
- Centre for Synthetic Microbiology (SYNMIKRO) Hans-Meerwein Strasse 6, Philipps-Universität Marburg, 35032, Marburg, Germany.,Fachbereich Chemie, Hans-Meerwein Strasse, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Christian Reimold
- Centre for Synthetic Microbiology (SYNMIKRO) Hans-Meerwein Strasse 6, Philipps-Universität Marburg, 35032, Marburg, Germany.,Fachbereich Chemie, Hans-Meerwein Strasse, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Joshua Stoll
- Centre for Synthetic Microbiology (SYNMIKRO) Hans-Meerwein Strasse 6, Philipps-Universität Marburg, 35032, Marburg, Germany.,Fachbereich Chemie, Hans-Meerwein Strasse, Philipps-Universität Marburg, 35032, Marburg, Germany
| | | | - Thomas Heimerl
- Centre for Synthetic Microbiology (SYNMIKRO) Hans-Meerwein Strasse 6, Philipps-Universität Marburg, 35032, Marburg, Germany.,Fachbereich Biologie, Karl-von-Frisch-Straße 10, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Hervé Joel Defeu Soufo
- Department of Microsystems Engineering - IMTEK, University of Freiburg, 79110, Freiburg, Germany
| | - Peter L Graumann
- Centre for Synthetic Microbiology (SYNMIKRO) Hans-Meerwein Strasse 6, Philipps-Universität Marburg, 35032, Marburg, Germany. .,Fachbereich Chemie, Hans-Meerwein Strasse, Philipps-Universität Marburg, 35032, Marburg, Germany.
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Jiang S, Ghoshdastider U, Narita A, Popp D, Robinson RC. Structural complexity of filaments formed from the actin and tubulin folds. Commun Integr Biol 2016; 9:e1242538. [PMID: 28042378 PMCID: PMC5193048 DOI: 10.1080/19420889.2016.1242538] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 09/21/2016] [Accepted: 09/23/2016] [Indexed: 11/09/2022] Open
Abstract
From yeast to man, an evolutionary distance of 1.3 billion years, the F-actin filament structure has been conserved largely in line with the 94% sequence identity. The situation is entirely different in bacteria. In comparison to eukaryotic actins, the bacterial actin-like proteins (ALPs) show medium to low levels of sequence identity. This is extreme in the case of the ParM family of proteins, which often display less than 20% identity. ParMs are plasmid segregation proteins that form the polymerizing motors that propel pairs of plasmids to the extremities of a cell prior to cell division, ensuring faithful inheritance of the plasmid. Recently, exotic ParM filament structures have been elucidated that show ParM filament geometries are not limited to the standard polar pair of strands typified by actin. Four-stranded non-polar ParM filaments existing as open or closed nanotubules are found in Clostridium tetani and Bacillus thuringiensis, respectively. These diverse architectures indicate that the actin fold is capable of forming a large variety of filament morphologies, and that the conception of the “actin” filament has been heavily influenced by its conservation in eukaryotes. Here, we review the history of the structure determination of the eukaryotic actin filament to give a sense of context for the discovery of the new ParM filament structures. We describe the novel ParM geometries and predict that even more complex actin-like filaments may exist in bacteria. Finally, we compare the architectures of filaments arising from the actin and tubulin folds and conclude that the basic units possess similar properties that can each form a range of structures. Thus, the use of the actin fold in microfilaments and the tubulin fold for microtubules likely arose from a wider range of filament possibilities, but became entrenched as those architectures in early eukaryotes.
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Affiliation(s)
- Shimin Jiang
- Institute of Molecular and Cell Biology, ASTAR (Agency for Science, Technology and Research) , Biopolis, Singapore
| | - Umesh Ghoshdastider
- Institute of Molecular and Cell Biology, ASTAR (Agency for Science, Technology and Research) , Biopolis, Singapore
| | - Akihiro Narita
- Nagoya University Graduate School of Science, Structural Biology Research Center and Division of Biological Sciences , Furo-cho , Chikusa-ku, Nagoya, Japan
| | - David Popp
- Institute of Molecular and Cell Biology, ASTAR (Agency for Science, Technology and Research) , Biopolis, Singapore
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, ASTAR (Agency for Science, Technology and Research), Biopolis, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, Singapore; School of Biological Sciences, Nanyang Technological University, Singapore; Lee Kong Chan School of Medicine, Singapore
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Jékely G. Origin and evolution of the self-organizing cytoskeleton in the network of eukaryotic organelles. Cold Spring Harb Perspect Biol 2014; 6:a016030. [PMID: 25183829 DOI: 10.1101/cshperspect.a016030] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The eukaryotic cytoskeleton evolved from prokaryotic cytomotive filaments. Prokaryotic filament systems show bewildering structural and dynamic complexity and, in many aspects, prefigure the self-organizing properties of the eukaryotic cytoskeleton. Here, the dynamic properties of the prokaryotic and eukaryotic cytoskeleton are compared, and how these relate to function and evolution of organellar networks is discussed. The evolution of new aspects of filament dynamics in eukaryotes, including severing and branching, and the advent of molecular motors converted the eukaryotic cytoskeleton into a self-organizing "active gel," the dynamics of which can only be described with computational models. Advances in modeling and comparative genomics hold promise of a better understanding of the evolution of the self-organizing cytoskeleton in early eukaryotes, and its role in the evolution of novel eukaryotic functions, such as amoeboid motility, mitosis, and ciliary swimming.
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Affiliation(s)
- Gáspár Jékely
- Max Planck Institute for Developmental Biology, 72076 Tuebingen, Germany
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