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Pormohammad A, Moradi M, Hommes JW, Pujol E, Naesens L, Vázquez S, Surewaard BGJ, Zarei M, Vazquez-Carrera M, Turner RJ. Novel pentafluorosulfanyl-containing triclocarban analogs selectively kill Gram-positive bacteria. Microbiol Spectr 2024; 12:e0007124. [PMID: 38700321 DOI: 10.1128/spectrum.00071-24] [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: 01/07/2024] [Accepted: 03/28/2024] [Indexed: 05/05/2024] Open
Abstract
Novel antimicrobial agents are needed to combat antimicrobial resistance. This study tested novel pentafluorosulfanyl-containing triclocarban analogs for their potential antibacterial efficacy. Standard procedures were used to produce pentafluorosulfanyl-containing triclocarban analogs. Twenty new compounds were tested against seven Gram-positive and Gram-negative indicator strains as well as 10 clinical isolates for their antibacterial and antibiofilm activity. Mechanistic investigations focused on damage to cell membrane, oxidizing reduced thiols, iron-sulfur clusters, and oxidative stress to explain the compounds' activity. Safety profiles were assessed using cytotoxicity experiments in eukaryotic cell lines. Following screening, selected components had significantly better antibacterial and antibiofilm activity against Gram-positive bacteria in lower concentrations in comparison to ciprofloxacin and gentamycin. For instance, one compound had a minimum inhibitory concentration of <0.0003 mM, but ciprofloxacin had 0.08 mM. Mechanistic studies show that these novel compounds do not affect reduced thiol content, iron-sulfur clusters, or hydrogen peroxide pathways. Their impact comes from Gram-positive bacterial cell membrane damage. Tests on cell culture toxicity and host component safety showed promise. Novel diarylurea compounds show promise as Gram-positive antimicrobials. These compounds offer prospects for study and optimization. IMPORTANCE The rise of antibiotic resistance among bacterial pathogens poses a significant threat to global health, underscoring the urgent need for novel antimicrobial agents. This study presents research on a promising class of novel compounds with potent antibacterial properties against Gram-positive bacteria, notably Staphylococcus aureus and MRSA. What sets these novel analogs apart is their superior efficacy at substantially lower concentrations compared with commonly used antibiotics like ciprofloxacin and gentamycin. Importantly, these compounds act by disrupting the bacterial cell membrane, offering a unique mechanism that could potentially circumvent existing resistance mechanisms. Preliminary safety assessments also highlight their potential for therapeutic use. This study not only opens new avenues for combating antibiotic-resistant infections but also underscores the importance of innovative chemical approaches in addressing the global antimicrobial resistance crisis.
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Affiliation(s)
- Ali Pormohammad
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
- MHCombiotic Inc., Calgary, Alberta, Canada
| | - Melika Moradi
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
- Department of Microbiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Science, Ahvaz, Iran
| | - Josefien W Hommes
- Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Eugènia Pujol
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Lieve Naesens
- Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Santiago Vázquez
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Bas G J Surewaard
- Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Mohammad Zarei
- Renal Division, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
- John B. Little Center for Radiation Sciences, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Manuel Vazquez-Carrera
- Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
- Pharmacology Unit, Faculty of Pharmacy and Food Sciences, University of Barcelona, Barcelona, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
| | - Raymond J Turner
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
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2
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Baum B, Spang A. On the origin of the nucleus: a hypothesis. Microbiol Mol Biol Rev 2023; 87:e0018621. [PMID: 38018971 PMCID: PMC10732040 DOI: 10.1128/mmbr.00186-21] [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] [Indexed: 11/30/2023] Open
Abstract
SUMMARYIn this hypothesis article, we explore the origin of the eukaryotic nucleus. In doing so, we first look afresh at the nature of this defining feature of the eukaryotic cell and its core functions-emphasizing the utility of seeing the eukaryotic nucleoplasm and cytoplasm as distinct regions of a common compartment. We then discuss recent progress in understanding the evolution of the eukaryotic cell from archaeal and bacterial ancestors, focusing on phylogenetic and experimental data which have revealed that many eukaryotic machines with nuclear activities have archaeal counterparts. In addition, we review the literature describing the cell biology of representatives of the TACK and Asgardarchaeaota - the closest known living archaeal relatives of eukaryotes. Finally, bringing these strands together, we propose a model for the archaeal origin of the nucleus that explains much of the current data, including predictions that can be used to put the model to the test.
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Affiliation(s)
- Buzz Baum
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Anja Spang
- Department of Marine Microbiology and Biogeochemistry, NIOZ, Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands
- Department of Evolutionary & Population Biology, Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Amsterdam, the Netherlands
- Department of Marine Microbiology and Biogeochemistry, NIOZ, Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands
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3
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Ma OX, Chong WG, Lee JKE, Cai S, Siebert CA, Howe A, Zhang P, Shi J, Surana U, Gan L. Cryo-ET detects bundled triple helices but not ladders in meiotic budding yeast. PLoS One 2022; 17:e0266035. [PMID: 35421110 PMCID: PMC9009673 DOI: 10.1371/journal.pone.0266035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 03/13/2022] [Indexed: 11/19/2022] Open
Abstract
In meiosis, cells undergo two sequential rounds of cell division, termed meiosis I and meiosis II. Textbook models of the meiosis I substage called pachytene show that nuclei have conspicuous 100-nm-wide, ladder-like synaptonemal complexes and ordered chromatin loops. It remains unknown if these cells have any other large, meiosis-related intranuclear structures. Here we present cryo-ET analysis of frozen-hydrated budding yeast cells before, during, and after pachytene. We found no cryo-ET densities that resemble dense ladder-like structures or ordered chromatin loops. Instead, we found large numbers of 12-nm-wide triple-helices that pack into ordered bundles. These structures, herein called meiotic triple helices (MTHs), are present in meiotic cells, but not in interphase cells. MTHs are enriched in the nucleus but not enriched in the cytoplasm. Bundles of MTHs form at the same timeframe as synaptonemal complexes (SCs) in wild-type cells and in mutant cells that are unable to form SCs. These results suggest that in yeast, SCs coexist with previously unreported large, ordered assemblies.
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Affiliation(s)
- Olivia X. Ma
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - Wen Guan Chong
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - Joy K. E. Lee
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - Shujun Cai
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - C. Alistair Siebert
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot, Oxfordshire, United Kingdom
| | - Andrew Howe
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot, Oxfordshire, United Kingdom
| | - Peijun Zhang
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot, Oxfordshire, United Kingdom
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Jian Shi
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - Uttam Surana
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Proteos, Singapore
- Bioprocessing Technology Institute, A*STAR, Singapore, Singapore
- Biotransformation Innovation Platform, A*STAR, Singapore, Singapore
- Department of Pharmacology, National University of Singapore, Singapore, Singapore
| | - Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
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Deryusheva EI, Machulin AV, Galzitskaya OV. Structural, Functional, and Evolutionary Characteristics of Proteins with Repeats. Mol Biol 2021. [DOI: 10.1134/s0026893321040038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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5
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Bateman A. Division of labour in a matrix, rather than phagocytosis or endosymbiosis, as a route for the origin of eukaryotic cells. Biol Direct 2020; 15:8. [PMID: 32345370 PMCID: PMC7187495 DOI: 10.1186/s13062-020-00260-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 02/25/2020] [Indexed: 12/13/2022] Open
Abstract
Abstract Two apparently irreconcilable models dominate research into the origin of eukaryotes. In one model, amitochondrial proto-eukaryotes emerged autogenously from the last universal common ancestor of all cells. Proto-eukaryotes subsequently acquired mitochondrial progenitors by the phagocytic capture of bacteria. In the second model, two prokaryotes, probably an archaeon and a bacterial cell, engaged in prokaryotic endosymbiosis, with the species resident within the host becoming the mitochondrial progenitor. Both models have limitations. A search was therefore undertaken for alternative routes towards the origin of eukaryotic cells. The question was addressed by considering classes of potential pathways from prokaryotic to eukaryotic cells based on considerations of cellular topology. Among the solutions identified, one, called here the “third-space model”, has not been widely explored. A version is presented in which an extracellular space (the third-space), serves as a proxy cytoplasm for mixed populations of archaea and bacteria to “merge” as a transitionary complex without obligatory endosymbiosis or phagocytosis and to form a precursor cell. Incipient nuclei and mitochondria diverge by division of labour. The third-space model can accommodate the reorganization of prokaryote-like genomes to a more eukaryote-like genome structure. Nuclei with multiple chromosomes and mitosis emerge as a natural feature of the model. The model is compatible with the loss of archaeal lipid biochemistry while retaining archaeal genes and provides a route for the development of membranous organelles such as the Golgi apparatus and endoplasmic reticulum. Advantages, limitations and variations of the “third-space” models are discussed. Reviewers This article was reviewed by Damien Devos, Buzz Baum and Michael Gray.
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Affiliation(s)
- Andrew Bateman
- Division of Experimental Medicine, Department of Medicine, McGill University, Glen Site Pavilion E, 1001 Boulevard Decarie, Montreal, Quebec, H4A 3J1, Canada. .,Centre for Translational Biology, Research Institute of McGill University Health Centre, Glen Site Pavilion E, 1001 Boulevard Decarie, Montreal, Quebec, H4A 3J1, Canada.
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6
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A New Census of Protein Tandem Repeats and Their Relationship with Intrinsic Disorder. Genes (Basel) 2020; 11:genes11040407. [PMID: 32283633 PMCID: PMC7230257 DOI: 10.3390/genes11040407] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 03/29/2020] [Accepted: 04/01/2020] [Indexed: 12/31/2022] Open
Abstract
Protein tandem repeats (TRs) are often associated with immunity-related functions and diseases. Since that last census of protein TRs in 1999, the number of curated proteins increased more than seven-fold and new TR prediction methods were published. TRs appear to be enriched with intrinsic disorder and vice versa. The significance and the biological reasons for this association are unknown. Here, we characterize protein TRs across all kingdoms of life and their overlap with intrinsic disorder in unprecedented detail. Using state-of-the-art prediction methods, we estimate that 50.9% of proteins contain at least one TR, often located at the sequence flanks. Positive linear correlation between the proportion of TRs and the protein length was observed universally, with Eukaryotes in general having more TRs, but when the difference in length is taken into account the difference is quite small. TRs were enriched with disorder-promoting amino acids and were inside intrinsically disordered regions. Many such TRs were homorepeats. Our results support that TRs mostly originate by duplication and are involved in essential functions such as transcription processes, structural organization, electron transport and iron-binding. In viruses, TRs are found in proteins essential for virulence.
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7
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Abstract
Biomolecular motors, such as the motor protein kinesin, can be used as off-the-shelf components to power hybrid nanosystems. These hybrid systems combine elements from the biological and synthetic toolbox of the nanoengineer and can be used to explore the applications and design principles of active nanosystems. Efforts to advance nanoscale engineering benefit greatly from biological and biophysical research into the operating principles of motor proteins and their biological roles. In return, the process of creating in vitro systems outside of the context of biology can lead to an improved understanding of the physical constraints creating the fitness landscape explored by evolution. However, our main focus is a holistic understanding of the engineering principles applying to systems integrating molecular motors in general. To advance this goal, we and other researchers have designed biomolecular motor-powered nanodevices, which sense, compute, and actuate. In addition to demonstrating that biological solutions can be mimicked in vitro, these devices often demonstrate new paradigms without parallels in current technology. Long-term trends in technology toward the deployment of ever smaller and more numerous motors and computers give us confidence that our work will become increasingly relevant. Here, our discussion aims to step back and look at the big picture. From our perspective, energy efficiency is a key and underappreciated metric in the design of synthetic motors. On the basis of an analogy to ecological principles, we submit that practical molecular motors have to have energy conversion efficiencies of more than 10%, a threshold only exceeded by motor proteins. We also believe that motor and system lifetime is a critical metric and an important topic of investigation. Related questions are if future molecular motors, by necessity, will resemble biomolecular motors in their softness and fragility and have to conform to the "universal performance characteristics of motors", linking the maximum force and mass of any motor, identified by Marden and Allen. The utilization of molecular motors for computing devices emphasizes the interesting relationship among the conversion of energy, extraction of work, and production of information. Our recent work touches upon these topics and discusses molecular clocks as well as a Landauer limit for robotics. What is on the horizon? Just as photovoltaics took advantage of progress in semiconductor fabrication to become commercially viable over a century, one can envision that engineers working with biomolecular motors leverage progress in biotechnology and drug development to create the engines of the future. However, the future source of energy is going to be electricity rather than fossil or biological fuels, a fact that has to be accounted for in our future efforts. In summary, we are convinced that past, ongoing, and future efforts to engineer with biomolecular motors are providing exciting demonstrations and fundamental insights as well as opportunities to wander freely across the borders of engineering, biology, and chemistry.
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Affiliation(s)
- Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Gadiel Saper
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
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8
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Stoddard PR, Williams TA, Garner E, Baum B. Evolution of polymer formation within the actin superfamily. Mol Biol Cell 2017; 28:2461-2469. [PMID: 28904122 PMCID: PMC5597319 DOI: 10.1091/mbc.e15-11-0778] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 07/13/2017] [Accepted: 07/18/2017] [Indexed: 01/02/2023] Open
Abstract
While many are familiar with actin as a well-conserved component of the eukaryotic cytoskeleton, it is less often appreciated that actin is a member of a large superfamily of structurally related protein families found throughout the tree of life. Actin-related proteins include chaperones, carbohydrate kinases, and other enzymes, as well as a staggeringly diverse set of proteins that use the energy from ATP hydrolysis to form dynamic, linear polymers. Despite differing widely from one another in filament structure and dynamics, these polymers play important roles in ordering cell space in bacteria, archaea, and eukaryotes. It is not known whether these polymers descended from a single ancestral polymer or arose multiple times by convergent evolution from monomeric actin-like proteins. In this work, we provide an overview of the structures, dynamics, and functions of this diverse set. Then, using a phylogenetic analysis to examine actin evolution, we show that the actin-related protein families that form polymers are more closely related to one another than they are to other nonpolymerizing members of the actin superfamily. Thus all the known actin-like polymers are likely to be the descendants of a single, ancestral, polymer-forming actin-like protein.
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Affiliation(s)
- Patrick R Stoddard
- Molecular and Cellular Biology, Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Tom A Williams
- School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Ethan Garner
- Molecular and Cellular Biology, Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Buzz Baum
- MRC-Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
- Institute of Physics of Living Systems, University College London, London WC1E 6BT, UK
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9
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10
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FtsZ filament capping by MciZ, a developmental regulator of bacterial division. Proc Natl Acad Sci U S A 2015; 112:E2130-8. [PMID: 25848052 DOI: 10.1073/pnas.1414242112] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cytoskeletal structures are dynamically remodeled with the aid of regulatory proteins. FtsZ (filamentation temperature-sensitive Z) is the bacterial homolog of tubulin that polymerizes into rings localized to cell-division sites, and the constriction of these rings drives cytokinesis. Here we investigate the mechanism by which the Bacillus subtilis cell-division inhibitor, MciZ (mother cell inhibitor of FtsZ), blocks assembly of FtsZ. The X-ray crystal structure reveals that MciZ binds to the C-terminal polymerization interface of FtsZ, the equivalent of the minus end of tubulin. Using in vivo and in vitro assays and microscopy, we show that MciZ, at substoichiometric levels to FtsZ, causes shortening of protofilaments and blocks the assembly of higher-order FtsZ structures. The findings demonstrate an unanticipated capping-based regulatory mechanism for FtsZ.
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11
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Erb ML, Kraemer JA, Coker JKC, Chaikeeratisak V, Nonejuie P, Agard DA, Pogliano J. A bacteriophage tubulin harnesses dynamic instability to center DNA in infected cells. eLife 2014; 3. [PMID: 25429514 PMCID: PMC4244570 DOI: 10.7554/elife.03197] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 10/22/2014] [Indexed: 11/13/2022] Open
Abstract
Dynamic instability, polarity, and spatiotemporal organization are hallmarks of the microtubule cytoskeleton that allow formation of complex structures such as the eukaryotic spindle. No similar structure has been identified in prokaryotes. The bacteriophage-encoded tubulin PhuZ is required to position DNA at mid-cell, without which infectivity is compromised. Here, we show that PhuZ filaments, like microtubules, stochastically switch from growing in a distinctly polar manner to catastrophic depolymerization (dynamic instability) both in vitro and in vivo. One end of each PhuZ filament is stably anchored near the cell pole to form a spindle-like array that orients the growing ends toward the phage nucleoid so as to position it near mid-cell. Our results demonstrate how a bacteriophage can harness the properties of a tubulin-like cytoskeleton for efficient propagation. This represents the first identification of a prokaryotic tubulin with the dynamic instability of microtubules and the ability to form a simplified bipolar spindle.
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Affiliation(s)
- Marcella L Erb
- Division of Biological Sciences, University of California, San Diego, La Jolla, United States
| | - James A Kraemer
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States
| | - Joanna K C Coker
- Division of Biological Sciences, University of California, San Diego, La Jolla, United States
| | - Vorrapon Chaikeeratisak
- Division of Biological Sciences, University of California, San Diego, La Jolla, United States
| | - Poochit Nonejuie
- Division of Biological Sciences, University of California, San Diego, La Jolla, United States
| | - David A Agard
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States
| | - Joe Pogliano
- Division of Biological Sciences, University of California, San Diego, La Jolla, United States
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12
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Abstract
The rod is a ubiquitous shape adopted by walled cells from diverse organisms ranging from bacteria to fungi to plants. Although rod-like shapes are found in cells of vastly different sizes and are constructed by diverse mechanisms, the geometric similarities among these shapes across kingdoms suggest that there are common evolutionary advantages, which may result from simple physical principles in combination with chemical and physiological constraints. Here, we review mechanisms of constructing rod-shaped cells and the bases of different biophysical models of morphogenesis, comparing and contrasting model organisms in different kingdoms. We then speculate on possible advantages of the rod shape, and suggest strategies for elucidating the relative importance of each of these advantages.
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13
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Polka JK, Kollman JM, Mullins RD. Accessory factors promote AlfA-dependent plasmid segregation by regulating filament nucleation, disassembly, and bundling. Proc Natl Acad Sci U S A 2014; 111:2176-81. [PMID: 24481252 PMCID: PMC3926056 DOI: 10.1073/pnas.1304127111] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In bacteria, some plasmids are partitioned to daughter cells by assembly of actin-like proteins (ALPs). The best understood ALP, ParM, has a core set of biochemical properties that contributes to its function, including dynamic instability, spontaneous nucleation, and bidirectional elongation. AlfA, an ALP that pushes plasmids apart in Bacillus, relies on a different set of underlying properties to segregate DNA. AlfA elongates unidirectionally and is not dynamically unstable; its assembly and disassembly are regulated by a cofactor, AlfB. Free AlfB breaks up AlfA bundles and promotes filament turnover. However, when AlfB is bound to the centromeric DNA sequence, parN, it forms a segrosome complex that nucleates and stabilizes AlfA filaments. When reconstituted in vitro, this system creates polarized, motile comet tails that associate by antiparallel filament bundling to form bipolar, DNA-segregating spindles.
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Affiliation(s)
- Jessica K. Polka
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158; and
| | - Justin M. Kollman
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada H3A 2B2
| | - R. Dyche Mullins
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158; and
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