51
|
Visco I, Hoege C, Hyman AA, Schwille P. In vitro Reconstitution of a Membrane Switch Mechanism for the Polarity Protein LGL. J Mol Biol 2016; 428:4828-4842. [PMID: 27720986 DOI: 10.1016/j.jmb.2016.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/28/2016] [Accepted: 10/01/2016] [Indexed: 12/24/2022]
Abstract
Cell polarity arises from a combination of interactions between biological molecules, such as activation, inhibition, and positive or negative feedback between specific polarity units. Activation and inhibition often take place in the form of a membrane binding switch. Lethal giant larvae (LGL), a conserved regulator of cell polarity in animals, was suggested to function as such a switch. LGL localizes to both the cytoplasm and, asymmetrically, the membrane. However, the spatial regulation mechanism of LGL membrane localization has remained unclear. For systematic elucidation, we set out to reconstitute a minimal polarity unit using a model membrane, Caenorhabditis elegans LGL (LGL-1), and atypical protein kinase C (aPKC) supposed to activate the membrane switch. We identified a membrane binding sequence (MBS) in LGL-1 by a screen in vivo, reconstituted LGL-1 membrane binding in vitro, and successfully implemented the membrane switch by aPKC phosphorylation activity, detaching LGL from membranes. Upon membrane binding, LGL-1 MBS folds into an alpha-helix in which three regions can be identified: a positively charged patch, a switch area containing the three aPKC phosphorylation sites, and a hydrophobic area probably buried in the membrane. Phosphorylation by aPKC dramatically reduces the binding affinity of the LGL-1 MBS to negatively charged model membranes, inducing its detachment. Specific residues in the MBS are critical for LGL-1 function in C. elegans.
Collapse
Affiliation(s)
- Ilaria Visco
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| | - Carsten Hoege
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Petra Schwille
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| |
Collapse
|
52
|
Guan L, Ma X, Zhang J, Liu JJ, Wang Y, Ding M. The Calponin Family Member CHDP-1 Interacts with Rac/CED-10 to Promote Cell Protrusions. PLoS Genet 2016; 12:e1006163. [PMID: 27415421 PMCID: PMC4944944 DOI: 10.1371/journal.pgen.1006163] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/10/2016] [Indexed: 02/02/2023] Open
Abstract
Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo.
Collapse
Affiliation(s)
- Liying Guan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Xuehua Ma
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jingyan Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jia-Jia Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai, China
| | - Yingchun Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai, China
| |
Collapse
|
53
|
Dajkovic A, Hinde E, MacKichan C, Carballido-Lopez R. Dynamic Organization of SecA and SecY Secretion Complexes in the B. subtilis Membrane. PLoS One 2016; 11:e0157899. [PMID: 27336478 PMCID: PMC4918944 DOI: 10.1371/journal.pone.0157899] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 06/07/2016] [Indexed: 12/21/2022] Open
Abstract
In prokaryotes, about one third of cellular proteins are translocated across the plasma membrane or inserted into it by concerted action of the cytoplasmic ATPase SecA and the universally conserved SecYEG heterotrimeric polypeptide-translocating pore. Secretion complexes have been reported to localize in specific subcellular sites in Bacillus subtilis. In this work, we used a combination of total internal reflection microscopy, scanning fluorescence correlation spectroscopy, and pair correlation function to study the localization and dynamics of SecA and SecY in growing Bacillus subtilis cells. Both SecA and SecY localized in transient and dynamic foci in the cytoplasmic membrane, which displayed no higher-level organization in helices. Foci of SecA and SecY were in constant flux with freely diffusing SecA and SecY molecules. Scanning FCS confirmed the existence of populations of cellular SecA and SecY molecules with a wide range of diffusion coefficients. Diffusion of SecY as an uncomplexed molecular species was short-lived and only local while SecY complexed with its protein partners traversed distances of over half a micrometer in the cell.
Collapse
Affiliation(s)
- Alex Dajkovic
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
- * E-mail:
| | - Elizabeth Hinde
- School of Medical Sciences, University of New South Wales, Sydney, Australia 2052
| | - Calum MacKichan
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - Rut Carballido-Lopez
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| |
Collapse
|
54
|
Pattern formation on membranes and its role in bacterial cell division. Curr Opin Cell Biol 2016; 38:52-9. [PMID: 26915065 DOI: 10.1016/j.ceb.2016.02.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 01/15/2016] [Accepted: 02/03/2016] [Indexed: 11/24/2022]
Abstract
Bacterial cell division is arguably one of the most central processes in biology. Despite the identification of many important molecular players, surprisingly little is yet known about the underlying physicochemical mechanisms. However, self-organized protein patterns play key roles during division of Escherichia coli, where division is initiated by the directed localization of FtsZ to the cell middle by an inhibitor gradient arising from pole-to-pole oscillations of MinCDE proteins. In vitro reconstitution studies have established that both the Min system and FtsZ with its membrane adaptor FtsA form dynamic energy-dependent patterns on membranes. Furthermore, recent in vivo and in vitro approaches have shown that Min patterns display rich dynamics in diverse geometries and respond to the progress of cytokinesis.
Collapse
|
55
|
Kusaka J, Shuto S, Imai Y, Ishikawa K, Saito T, Natori K, Matsuoka S, Hara H, Matsumoto K. Septal localization by membrane targeting sequences and a conserved sequence essential for activity at the COOH-terminus of Bacillus subtilis cardiolipin synthase. Res Microbiol 2015; 167:202-14. [PMID: 26708983 DOI: 10.1016/j.resmic.2015.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 11/23/2015] [Accepted: 11/27/2015] [Indexed: 11/16/2022]
Abstract
The acidic phospholipid cardiolipin (CL) is localized on polar and septal membranes and plays an important physiological role in Bacillus subtilis cells. ClsA, the enzyme responsible for CL synthesis, is also localized on septal membranes. We found that GFP fusion proteins of the enzyme with NH2-terminal and internal deletions retained septal localization. However, derivatives with deletions starting from the COOH-terminus (Leu482) ceased to localize to the septum once the deletion passed the Ile residue at 448, indicating that the sequence responsible for septal localization is confined within a short distance from the COOH-terminus. Two sequences, Ile436-Leu450 and Leu466-Leu478, are predicted to individually form an amphipathic α-helix. This configuration is known as a membrane targeting sequence (MTS) and we therefore refer to them as MTS2 and MTS1, respectively. Either one has the ability to affect septal localization, and each of these sequences by itself localizes to the septum. Membrane association of the constructs of this enzyme containing the MTSs was verified by subcellular fractionation of the cells. CL synthesis, in contrast, was abolished after deleting just the last residue, Leu482, in the COOH-terminal four amino acid residue sequence, Ser-Pro-Ile-Leu, which is highly conserved among bacterial CL synthases.
Collapse
Affiliation(s)
- Jin Kusaka
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Satoshi Shuto
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Yukiko Imai
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Kazuki Ishikawa
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Tomo Saito
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Kohei Natori
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Satoshi Matsuoka
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Hiroshi Hara
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan
| | - Kouji Matsumoto
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan.
| |
Collapse
|
56
|
Ortiz C, Natale P, Cueto L, Vicente M. The keepers of the ring: regulators of FtsZ assembly. FEMS Microbiol Rev 2015; 40:57-67. [PMID: 26377318 DOI: 10.1093/femsre/fuv040] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/21/2015] [Indexed: 11/13/2022] Open
Abstract
FtsZ, a GTPase distributed in the cytoplasm of most bacteria, is the major component of the machinery responsible for division (the divisome) in Escherichia coli. It interacts with additional proteins that contribute to its function forming a ring at the midcell that is essential to constrict the membrane. FtsZ is indirectly anchored to the membrane and it is prevented from polymerizing at locations where septation is undesired. Several properties of FtsZ are mediated by other proteins that function as keepers of the ring. ZipA and FtsA serve to anchor the ring, and together with a set of Zap proteins, they stabilize it. The MinCDE and SlmA proteins prevent the polymerization of FtsZ at sites other than the midcell. Finally, ClpP degrades FtsZ, an action prevented by ZipA. Many of the FtsZ keepers interact with FtsZ through a central hub located at its carboxy terminal end.
Collapse
Affiliation(s)
- Cristina Ortiz
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), C/ Darwin 3, Madrid 28049, Spain
| | - Paolo Natale
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), C/ Darwin 3, Madrid 28049, Spain
| | - Laura Cueto
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), C/ Darwin 3, Madrid 28049, Spain
| | - Miguel Vicente
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), C/ Darwin 3, Madrid 28049, Spain
| |
Collapse
|
57
|
Membrane Stored Curvature Elastic Stress Modulates Recruitment of Maintenance Proteins PspA and Vipp1. mBio 2015; 6:e01188-15. [PMID: 26330516 PMCID: PMC4556811 DOI: 10.1128/mbio.01188-15] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phage shock protein A (PspA), which is responsible for maintaining inner membrane integrity under stress in enterobacteria, and vesicle-inducting protein in plastids 1 (Vipp1), which functions for membrane maintenance and thylakoid biogenesis in cyanobacteria and plants, are similar peripheral membrane-binding proteins. Their homologous N-terminal amphipathic helices are required for membrane binding; however, the membrane features recognized and required for expressing their functionalities have remained largely uncharacterized. Rigorously controlled, in vitro methodologies with lipid vesicles and purified proteins were used in this study and provided the first biochemical and biophysical characterizations of membrane binding by PspA and Vipp1. Both proteins are found to sense stored curvature elastic (SCE) stress and anionic lipids within the membrane. PspA has an enhanced sensitivity for SCE stress and a higher affinity for the membrane than Vipp1. These variations in binding may be crucial for some of the proteins’ differing roles in vivo. Assays probing the transcriptional regulatory function of PspA in the presence of vesicles showed that a relief of transcription inhibition occurs in an SCE stress-specific manner. This in vitro recapitulation of membrane stress-dependent transcription control suggests that the Psp response may be mounted in vivo when a cell’s inner membrane experiences increased SCE stress. All cell types maintain the integrity of their membrane systems. One widely distributed membrane stress response system in bacteria is the phage shock protein (Psp) system. The central component, peripheral membrane protein PspA, which mitigates inner membrane stress in bacteria, has a counterpart, Vipp1, which functions for membrane maintenance and thylakoid biogenesis in plants and photosynthetic bacteria. Membrane association of both these proteins is accepted as playing a pivotal role in their functions. Here we show that direct membrane binding by PspA and Vipp1 is driven by two physio-chemical signals, one of which is membrane stress specific. Our work points to alleviation of membrane stored curvature elastic stress by amphipathic helix insertions as an attractive mechanism for membrane maintenance by PspA and Vipp1. Furthermore, the identification of a physical, stress-related membrane signal suggests a unilateral mechanism that promotes both binding of PspA and induction of the Psp response.
Collapse
|
58
|
Aberle D, Oetter KM, Meyers G. Lipid Binding of the Amphipathic Helix Serving as Membrane Anchor of Pestivirus Glycoprotein Erns. PLoS One 2015; 10:e0135680. [PMID: 26270479 PMCID: PMC4536213 DOI: 10.1371/journal.pone.0135680] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 07/26/2015] [Indexed: 01/30/2023] Open
Abstract
Pestiviruses express a peculiar protein named Erns representing envelope glycoprotein and RNase, which is important for control of the innate immune response and persistent infection. The latter functions are connected with secretion of a certain amount of Erns from the infected cell. Retention/secretion of Erns is most likely controlled by its unusual membrane anchor, a long amphipathic helix attached in plane to the membrane. Here we present results of experiments conducted with a lipid vesicle sedimentation assay able to separate lipid-bound from unbound protein dissolved in the water phase. Using this technique we show that a protein composed of tag sequences and the carboxyterminal 65 residues of Erns binds specifically to membrane vesicles with a clear preference for compositions containing negatively charged lipids. Mutations disturbing the helical folding and/or amphipathic character of the anchor as well as diverse truncations and exchange of amino acids important for intracellular retention of Erns had no or only small effects on the proteins membrane binding. This result contrasts the dramatically increased secretion rates observed for Erns proteins with equivalent mutations within cells. Accordingly, the ratio of secreted versus cell retained Erns is not determined by the lipid affinity of the membrane anchor.
Collapse
Affiliation(s)
- Daniel Aberle
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
| | - Kay-Marcus Oetter
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
- * E-mail:
| |
Collapse
|
59
|
Schuhmacher JS, Thormann KM, Bange G. How bacteria maintain location and number of flagella? FEMS Microbiol Rev 2015. [PMID: 26195616 DOI: 10.1093/femsre/fuv034] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Bacteria differ in number and location of their flagella that appear in regular patterns at the cell surface (flagellation pattern). Despite the plethora of bacterial species, only a handful of these patterns exist. The correct flagellation pattern is a prerequisite for motility, but also relates to biofilm formation and the pathogenicity of disease-causing flagellated bacteria. However, the mechanisms that maintain location and number of flagella are far from being understood. Here, we review our knowledge on mechanisms that enable bacteria to maintain their appropriate flagellation pattern. While some peritrichous flagellation patterns might occur by rather simple stochastic processes, other bacterial species appear to rely on landmark systems to define the designated flagellar position. Such landmarks are the Tip system of Caulobacter crescentus or the signal recognition particle (SRP)-GTPase FlhF and the MinD/ParA-type ATPase FlhG (synonyms: FleN, YlxH and MinD2). The latter two proteins constitute a regulatory circuit essential for diverse flagellation patterns in many Gram-positive and negative species. The interactome of FlhF/G (e.g. C-ring proteins FliM, FliN, FliY or the transcriptional regulator FleQ/FlrA) seems evolutionary adapted to meet the specific needs for a respective pattern. This variability highlights the importance of the correct flagellation pattern for motile species.
Collapse
Affiliation(s)
- Jan S Schuhmacher
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse, D-35043 Marburg, Germany
| | - Kai M Thormann
- Justus-Liebig University, Department of Microbiology and Molecular Biology, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
| | - Gert Bange
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse, D-35043 Marburg, Germany
| |
Collapse
|
60
|
Matsumoto K, Hara H, Fishov I, Mileykovskaya E, Norris V. The membrane: transertion as an organizing principle in membrane heterogeneity. Front Microbiol 2015; 6:572. [PMID: 26124753 PMCID: PMC4464175 DOI: 10.3389/fmicb.2015.00572] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/25/2015] [Indexed: 01/05/2023] Open
Abstract
The bacterial membrane exhibits a significantly heterogeneous distribution of lipids and proteins. This heterogeneity results mainly from lipid-lipid, protein-protein, and lipid-protein associations which are orchestrated by the coupled transcription, translation and insertion of nascent proteins into and through membrane (transertion). Transertion is central not only to the individual assembly and disassembly of large physically linked groups of macromolecules (alias hyperstructures) but also to the interactions between these hyperstructures. We review here these interactions in the context of the processes in Bacillus subtilis and Escherichia coli of nutrient sensing, membrane synthesis, cytoskeletal dynamics, DNA replication, chromosome segregation, and cell division.
Collapse
Affiliation(s)
- Kouji Matsumoto
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Hiroshi Hara
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Itzhak Fishov
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-ShevaIsrael
| | - Eugenia Mileykovskaya
- Department of Biochemistry and Molecular Biology, University of Texas Medical School at HoustonHouston, TX, USA
| | - Vic Norris
- Laboratory of Microbiology Signals and Microenvironment EA 4312, Department of Science, University of Rouen, Mont-Saint-AignanFrance
| |
Collapse
|
61
|
Arumugam S, Petrov EP, Schwille P. Cytoskeletal pinning controls phase separation in multicomponent lipid membranes. Biophys J 2015; 108:1104-13. [PMID: 25762322 PMCID: PMC4375424 DOI: 10.1016/j.bpj.2014.12.050] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 12/22/2014] [Accepted: 12/23/2014] [Indexed: 11/22/2022] Open
Abstract
We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar vesicles by the prokaryotic tubulin homolog, FtsZ, on phase separation in freestanding lipid membranes. FtsZ has been modified to interact with the membrane through a membrane targeting sequence from the prokaryotic protein MinD. FtsZ with the attached membrane targeting sequence efficiently forms a highly interconnected network on membranes with a concentration-dependent mesh size, much similar to the eukaryotic cytoskeletal network underlying the plasma membrane. Using giant unilamellar vesicles formed from a quaternary lipid mixture, we demonstrate that the artificial membrane-associated cytoskeleton, on the one hand, suppresses large-scale phase separation below the phase transition temperature, and, on the other hand, preserves phase separation above the transition temperature. Our experimental observations support the ideas put forward in our previous simulation study: In particular, the picket fence effect on phase separation may explain why micrometer-scale membrane domains are observed in isolated, cytoskeleton-free giant plasma membrane vesicles, but not in intact cell membranes. The experimentally observed suppression of large-scale phase separation much below the transition temperatures also serves as an argument in favor of the cryoprotective role of the cytoskeleton.
Collapse
Affiliation(s)
- Senthil Arumugam
- Institut Curie, Centre de Recherche, Paris, France; CNRS, UMR 168, Physico-chimie Curie, Paris, France; CNRS, UMR 3666, Endocytic Trafficking and Therapeutic Delivery Group, Paris, France
| | - Eugene P Petrov
- Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Am Klopferspitz 18, Martinsried, Germany.
| | - Petra Schwille
- Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Am Klopferspitz 18, Martinsried, Germany.
| |
Collapse
|
62
|
Carr M, MacPhee CE. Membrainy: a 'smart', unified membrane analysis tool. SOURCE CODE FOR BIOLOGY AND MEDICINE 2015; 10:3. [PMID: 26060507 PMCID: PMC4460882 DOI: 10.1186/s13029-015-0033-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 02/19/2015] [Indexed: 11/10/2022]
Abstract
BACKGROUND The study of biological membranes using Molecular Dynamics has become an increasingly popular means by which to investigate the interactions of proteins, peptides and potentials with lipid bilayers. These interactions often result in changes to the properties of the lipids which can modify the behaviour of the membrane. Membrainy is a unified membrane analysis tool that contains a broad spectrum of analytical techniques to enable: measurement of acyl chain order parameters; presentation of 2D surface and thickness maps; determination of lateral and axial headgroup orientations; measurement of bilayer and leaflet thickness; analysis of the annular shell surrounding membrane-embedded objects; quantification of gel percentage; time evolution of the transmembrane voltage; area per lipid calculations; and quantification of lipid mixing/demixing entropy. RESULTS Each analytical component within Membrainy has been tested on a variety of lipid bilayer systems and was found to be either comparable to or an improvement upon existing software. For the analytical techniques that have no direct comparable software, our results were confirmed with experimental data. CONCLUSIONS Membrainy is a user-friendly, intelligent membrane analysis tool that automatically interprets a variety of input formats and force fields, is compatible with both single and double bilayers, and capable of handling asymmetric bilayers and lipid flip-flopping. Membrainy has been designed for ease of use, requiring no installation or configuration and minimal user-input to operate.
Collapse
Affiliation(s)
- Matthew Carr
- Institute for Condensed Matter and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh, UK
| | - Cait E MacPhee
- Institute for Condensed Matter and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh, UK
| |
Collapse
|
63
|
MinD-like ATPase FlhG effects location and number of bacterial flagella during C-ring assembly. Proc Natl Acad Sci U S A 2015; 112:3092-7. [PMID: 25733861 DOI: 10.1073/pnas.1419388112] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The number and location of flagella, bacterial organelles of locomotion, are species specific and appear in regular patterns that represent one of the earliest taxonomic criteria in microbiology. However, the mechanisms that reproducibly establish these patterns during each round of cell division are poorly understood. FlhG (previously YlxH) is a major determinant for a variety of flagellation patterns. Here, we show that FlhG is a structural homolog of the ATPase MinD, which serves in cell-division site determination. Like MinD, FlhG forms homodimers that are dependent on ATP and lipids. It interacts with a complex of the flagellar C-ring proteins FliM and FliY (also FliN) in the Gram-positive, peritrichous-flagellated Bacillus subtilis and the Gram-negative, polar-flagellated Shewanella putrefaciens. FlhG interacts with FliM/FliY in a nucleotide-independent manner and activates FliM/FliY to assemble with the C-ring protein FliG in vitro. FlhG-driven assembly of the FliM/FliY/FliG complex is strongly enhanced by ATP and lipids. The protein shows a highly dynamic subcellular distribution between cytoplasm and flagellar basal bodies, suggesting that FlhG effects flagellar location and number during assembly of the C-ring. We describe the molecular evolution of a MinD-like ATPase into a flagellation pattern effector and suggest that the underappreciated structural diversity of the C-ring proteins might contribute to the formation of different flagellation patterns.
Collapse
|
64
|
Kretschmer S, Schwille P. Toward Spatially Regulated Division of Protocells: Insights into the E. coli Min System from in Vitro Studies. Life (Basel) 2014; 4:915-28. [PMID: 25513760 PMCID: PMC4284474 DOI: 10.3390/life4040915] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 11/25/2014] [Accepted: 12/03/2014] [Indexed: 11/16/2022] Open
Abstract
For reconstruction of controlled cell division in a minimal cell model, or protocell, a positioning mechanism that spatially regulates division is indispensable. In Escherichia coli, the Min proteins oscillate from pole to pole to determine the division site by inhibition of the primary divisome protein FtsZ anywhere but in the cell middle. Remarkably, when reconstituted under defined conditions in vitro, the Min proteins self-organize into spatiotemporal patterns in the presence of a lipid membrane and ATP. We review recent progress made in studying the Min system in vitro, particularly focusing on the effects of various physicochemical parameters and boundary conditions on pattern formation. Furthermore, we discuss implications and challenges for utilizing the Min system for division site placement in protocells.
Collapse
Affiliation(s)
- Simon Kretschmer
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany.
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany.
| |
Collapse
|
65
|
Conti J, Viola MG, Camberg JL. The bacterial cell division regulators MinD and MinC form polymers in the presence of nucleotide. FEBS Lett 2014; 589:201-6. [PMID: 25497011 DOI: 10.1016/j.febslet.2014.11.047] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 11/20/2022]
Abstract
The Min system of proteins, consisting of MinC, MinD and MinE, is essential for normal cell division in Escherichia coli. MinC forms a polar gradient to restrict placement of the division septum to midcell. MinC localization occurs through a direct interaction with MinD, a membrane-associating Par-like ATPase. MinE stimulates ATP hydrolysis by MinD, thereby releasing MinD from the membrane. Here, we show that MinD forms polymers with MinC and ATP without the addition of phospholipids. The topological regulator MinE induces disassembly of MinCD polymers. Two MinD mutant proteins, MinD(K11A) and MinD(ΔMTS15), are unable to form polymers with MinC.
Collapse
Affiliation(s)
- Joseph Conti
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, RI, USA
| | - Marissa G Viola
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, RI, USA
| | - Jodi L Camberg
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, RI, USA; Department of Nutrition and Food Sciences, The University of Rhode Island, Kingston, RI, USA.
| |
Collapse
|
66
|
Vecchiarelli AG, Li M, Mizuuchi M, Mizuuchi K. Differential affinities of MinD and MinE to anionic phospholipid influence Min patterning dynamics in vitro. Mol Microbiol 2014; 93:453-63. [PMID: 24930948 DOI: 10.1111/mmi.12669] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2014] [Indexed: 11/28/2022]
Abstract
The E. coli Min system forms a cell-pole-to-cell-pole oscillator that positions the divisome at mid-cell. The MinD ATPase binds the membrane and recruits the cell division inhibitor MinC. MinE interacts with and releases MinD (and MinC) from the membrane. The chase of MinD by MinE creates the in vivo oscillator that maintains a low level of the division inhibitor at mid-cell. In vitro reconstitution and visualization of Min proteins on a supported lipid bilayer has provided significant advances in understanding Min patterns in vivo. Here we studied the effects of flow, lipid composition, and salt concentration on Min patterning. Flow and no-flow conditions both supported Min protein patterns with somewhat different characteristics. Without flow, MinD and MinE formed spiraling waves. MinD and, to a greater extent MinE, have stronger affinities for anionic phospholipid. MinD-independent binding of MinE to anionic lipid resulted in slower and narrower waves. MinE binding to the bilayer was also more susceptible to changes in ionic strength than MinD. We find that modulating protein diffusion with flow, or membrane binding affinities with changes in lipid composition or salt concentration, can differentially affect the retention time of MinD and MinE, leading to spatiotemporal changes in Min patterning.
Collapse
Affiliation(s)
- Anthony G Vecchiarelli
- Laboratory of Molecular Biology, National Institute of Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | | | | | | |
Collapse
|
67
|
Chromosome segregation by the Escherichia coli Min system. Mol Syst Biol 2014; 9:686. [PMID: 24022004 PMCID: PMC3792344 DOI: 10.1038/msb.2013.44] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 08/07/2013] [Indexed: 12/26/2022] Open
Abstract
The mechanisms underlying chromosome segregation in prokaryotes remain a subject of debate and no unifying view has yet emerged. Given that the initial disentanglement of duplicated chromosomes could be achieved by purely entropic forces, even the requirement of an active prokaryotic segregation machinery has been questioned. Using computer simulations, we show that entropic forces alone are not sufficient to achieve and maintain full separation of chromosomes. This is, however, possible by assuming repeated binding of chromosomes along a gradient of membrane-associated tethering sites toward the poles. We propose that, in Escherichia coli, such a gradient of membrane tethering sites may be provided by the oscillatory Min system, otherwise known for its role in selecting the cell division site. Consistent with this hypothesis, we demonstrate that MinD binds to DNA and tethers it to the membrane in an ATP-dependent manner. Taken together, our combined theoretical and experimental results suggest the existence of a novel mechanism of chromosome segregation based on the Min system, further highlighting the importance of active segregation of chromosomes in prokaryotic cell biology.
Collapse
|
68
|
Bonny M, Fischer-Friedrich E, Loose M, Schwille P, Kruse K. Membrane binding of MinE allows for a comprehensive description of Min-protein pattern formation. PLoS Comput Biol 2013; 9:e1003347. [PMID: 24339757 PMCID: PMC3854456 DOI: 10.1371/journal.pcbi.1003347] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/03/2013] [Indexed: 11/23/2022] Open
Abstract
The rod-shaped bacterium Escherichia coli selects the cell center as site of division with the help of the proteins MinC, MinD, and MinE. This protein system collectively oscillates between the two cell poles by alternately binding to the membrane in one of the two cell halves. This dynamic behavior, which emerges from the interaction of the ATPase MinD and its activator MinE on the cell membrane, has become a paradigm for protein self-organization. Recently, it has been found that not only the binding of MinD to the membrane, but also interactions of MinE with the membrane contribute to Min-protein self-organization. Here, we show that by accounting for this finding in a computational model, we can comprehensively describe all observed Min-protein patterns in vivo and in vitro. Furthermore, by varying the system's geometry, our computations predict patterns that have not yet been reported. We confirm these predictions experimentally. Cellular protein structures have long been suggested to form by protein self-organization. A particularly clear example is provided by the proteins MinC, MinD, and MinE selecting the center as site of cell division in the rod-shaped bacterium Escherichia coli. Based on binding of MinD to the cytoplasmic membrane and an antagonistic action of MinE, which induces the release of MinD into the cytoplasm, these proteins oscillate from pole to pole, where they inhibit cell division. Supporting the idea of self-organization being the cause of the Min oscillations, purified Min proteins were found to spontaneously form traveling waves on supported lipid bilayers. A comprehensive understanding of the Min patterns formed under various conditions remains elusive. We have performed a computational analysis of Min-protein dynamics taking into account the recently discovered persistent action of MinE. We show that this property allows to reproduce all observed Min-protein patterns in a unified framework. Furthermore, our analysis predicts new structures, which we observed experimentally. Our study highlights that mechanisms underlying the spontaneous formation of protein patterns under purified in vitro conditions can also generate patterns inside complex intracellular environments.
Collapse
Affiliation(s)
- Mike Bonny
- Theoretische Physik, Universität des Saarlandes, Saarbrücken, Germany
| | - Elisabeth Fischer-Friedrich
- Max-Planck-Institut für Zellbiologie und Genetik, Dresden, Germany
- Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany
| | - Martin Loose
- Department of Systems Biology, Harvard Medical School, Boston, Massachussetts, United States of America
| | | | - Karsten Kruse
- Theoretische Physik, Universität des Saarlandes, Saarbrücken, Germany
- * E-mail:
| |
Collapse
|
69
|
Structural and genetic analyses reveal the protein SepF as a new membrane anchor for the Z ring. Proc Natl Acad Sci U S A 2013; 110:E4601-10. [PMID: 24218584 DOI: 10.1073/pnas.1313978110] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A key step in bacterial cell division is the polymerization of the tubulin homolog FtsZ at midcell. FtsZ polymers are anchored to the cell membrane by FtsA and are required for the assembly of all other cell division proteins. In Gram-positive and cyanobacteria, FtsZ filaments are aligned by the protein SepF, which in vitro polymerizes into large rings that bundle FtsZ filaments. Here we describe the crystal structure of the only globular domain of SepF, located within the C-terminal region. Two-hybrid data revealed that this domain comprises the FtsZ binding site, and EM analyses showed that it is sufficient for ring formation, which is explained by the filaments in the crystals of SepF. Site-directed mutagenesis, gel filtration, and analytical ultracentrifugation indicated that dimers form the basic units of SepF filaments. High-resolution structured illumination microscopy suggested that SepF is membrane associated, and it turned out that purified SepF not only binds to lipid membranes, but also recruits FtsZ. Further genetic and biochemical analyses showed that an amphipathic helix at the N terminus functions as the membrane-binding domain, making SepF a unique membrane anchor for the FtsZ ring. This clarifies why Bacillus subtilis grows without FtsA or the putative membrane anchor EzrA and why bacteria lacking FtsA contain SepF homologs. Both FtsA and SepF use an amphipathic helix for membrane binding. These helices prefer positively curved membranes due to relaxed lipid density; therefore this type of membrane anchor may assist in keeping the Z ring positioned at the strongly curved leading edge of the developing septum.
Collapse
|
70
|
An JY, Kim TG, Park KR, Lee JG, Youn HS, Lee Y, Kang JY, Kang GB, Eom SH. Crystal structure of the N-terminal domain of MinC dimerized via domain swapping. JOURNAL OF SYNCHROTRON RADIATION 2013; 20:984-8. [PMID: 24121353 PMCID: PMC3795569 DOI: 10.1107/s0909049513022760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 08/13/2013] [Indexed: 06/02/2023]
Abstract
Proper cell division at the mid-site of gram-negative bacteria reflects critical regulation by the min system (MinC, MinD and MinE) of the cytokinetic Z ring, which is a polymer composed of FtsZ subunits. MinC and MinD act together to inhibit aberrantly positioned Z-ring formation. MinC consists of two domains: an N-terminal domain (MinCNTD), which interacts with FtsZ and inhibits FtsZ polymerization, and a C-terminal domain (MinCCTD), which interacts with MinD and inhibits the bundling of FtsZ filaments. These two domains reportedly function together, and both are essential for normal cell division. The full-length dimeric structure of MinC from Thermotoga maritima has been reported, and shows that MinC dimerization occurs via MinCCTD; MinCNTD is not involved in dimerization. Here the crystal structure of Escherichia coli MinCNTD (EcoMinCNTD) is reported. EcoMinCNTD forms a dimer via domain swapping between the first β strands in each subunit. It is therefore suggested that the dimerization of full-length EcoMinC occurs via both MinCCTD and MinCNTD, and that the dimerized EcoMinCNTD likely plays an important role in inhibiting aberrant Z-ring localization.
Collapse
Affiliation(s)
- Jun Yop An
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Tae Gyun Kim
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Kyoung Ryoung Park
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Jung-Gyu Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Hyung-Seop Youn
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Youngjin Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Jung Youn Kang
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Gil Bu Kang
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Soo Hyun Eom
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
- Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| |
Collapse
|
71
|
Martos A, Petrasek Z, Schwille P. Propagation of MinCDE waves on free-standing membranes. Environ Microbiol 2013; 15:3319-26. [PMID: 24118679 DOI: 10.1111/1462-2920.12295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 09/24/2013] [Indexed: 11/30/2022]
Abstract
As a spatial modulator of cytokinesis in Escherichia coli, the Min system cooperates with the nucleoid occlusion mechanism to target the divisome assembly towards mid-cell. Based on a reaction-diffusion mechanism powered by ATP (adenosine triphosphate) hydrolysis, the Min proteins propagate in waves on the cell membrane, resulting in oscillations between the cell poles, thus preventing the formation of the division ring everywhere but in the cell centre. The dynamic behaviour of Min proteins has been successfully reconstructed in vitro on supported lipid bilayers (SLBs), reproducing many of the features observed in the cell. However, there has been a marked discrepancy between the speed of propagation of Min protein waves in vitro, compared with the cellular system. A very plausible explanation is the different mobility of proteins on model membranes, compared with the inner membrane of bacteria. To quantitatively demonstrate how membrane diffusion influences Min wave propagation, we compared Min waves on SLBs with free-standing giant unilamellar vesicles (GUV) membranes which display higher fluidity. Intriguingly, the propagation velocity and wavelength on GUVs are three times higher than those reported on supported bilayers, but the wave period is conserved. This suggests that the shorter spatial period of the patterns in vivo might indeed be primarily explained by lower diffusion coefficients of proteins on the bacterial inner membrane.
Collapse
Affiliation(s)
- Ariadna Martos
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152, Martinsried, Germany
| | | | | |
Collapse
|
72
|
Discovery of a selective NaV1.7 inhibitor from centipede venom with analgesic efficacy exceeding morphine in rodent pain models. Proc Natl Acad Sci U S A 2013; 110:17534-9. [PMID: 24082113 DOI: 10.1073/pnas.1306285110] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Loss-of-function mutations in the human voltage-gated sodium channel NaV1.7 result in a congenital indifference to pain. Selective inhibitors of NaV1.7 are therefore likely to be powerful analgesics for treating a broad range of pain conditions. Herein we describe the identification of µ-SLPTX-Ssm6a, a unique 46-residue peptide from centipede venom that potently inhibits NaV1.7 with an IC50 of ∼25 nM. µ-SLPTX-Ssm6a has more than 150-fold selectivity for NaV1.7 over all other human NaV subtypes, with the exception of NaV1.2, for which the selectivity is 32-fold. µ-SLPTX-Ssm6a contains three disulfide bonds with a unique connectivity pattern, and it has no significant sequence homology with any previously characterized peptide or protein. µ-SLPTX-Ssm6a proved to be a more potent analgesic than morphine in a rodent model of chemical-induced pain, and it was equipotent with morphine in rodent models of thermal and acid-induced pain. This study establishes µ-SPTX-Ssm6a as a promising lead molecule for the development of novel analgesics targeting NaV1.7, which might be suitable for treating a wide range of human pain pathologies.
Collapse
|
73
|
Lu F, Taghbalout A. Membrane association via an amino-terminal amphipathic helix is required for the cellular organization and function of RNase II. J Biol Chem 2013; 288:7241-51. [PMID: 23344958 DOI: 10.1074/jbc.m112.408674] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The subcellular localization of the exoribonuclease RNase II is not known despite the advanced biochemical characterization of the enzyme. Here we report that RNase II is organized into cellular structures that appear to coil around the Escherichia coli cell periphery and that RNase II is associated with the cytoplasmic membrane by its amino-terminal amphipathic helix. The helix also acts as an autonomous transplantable membrane binding domain capable of directing normally cytoplasmic proteins to the membrane. Assembly of the organized cellular structures of RNase II required the RNase II amphipathic membrane binding domain. Co-immunoprecipitation of the protein from cell extracts indicated that RNase II interacts with itself. The RNase II self-interaction and the ability of the protein to assemble into organized cellular structures required the membrane binding domain. The ability of RNase II to maintain cell viability in the absence of the exoribonuclease polynucleotide phosphorylase was markedly diminished when the RNase II cellular structures were lost due to changes in the amphipathicity of the amino-terminal helix, suggesting that membrane association and assembly of RNase II into organized cellular structures play an important role in the normal function of the protein within the bacterial cell.
Collapse
Affiliation(s)
- Feng Lu
- Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA
| | | |
Collapse
|
74
|
Renner LD, Weibel DB. MinD and MinE interact with anionic phospholipids and regulate division plane formation in Escherichia coli. J Biol Chem 2012; 287:38835-44. [PMID: 23012351 DOI: 10.1074/jbc.m112.407817] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Min proteins (MinC, MinD, and MinE) form a pole-to-pole oscillator that controls the spatial assembly of the division machinery in Escherichia coli cells. Previous studies identified that interactions of MinD with phospholipids positioned the Min machinery at the membrane. We extend these studies by measuring the affinity, kinetics, and ATPase activity of E. coli MinD, MinE, and MinDE binding to supported lipid bilayers containing varying compositions of anionic phospholipids. Using quartz crystal microbalance measurements, we found that the binding affinity (K(d)) for the interaction of recombinant E. coli MinD and MinE with lipid bilayers increased with increasing concentration of the anionic phospholipids phosphatidylglycerol and cardiolipin. The K(d) for MinD (1.8 μM) in the presence of ATP was smaller than for MinE (12.1 μM) binding to membranes consisting of 95:5 phosphatidylcholine/cardiolipin. The simultaneous binding of MinD and MinE to membranes revealed that increasing the concentration of anionic phospholipid stimulates the initial rate of adsorption (k(on)). The ATPase activity of MinD decreased in the presence of anionic phospholipids. These results indicate that anionic lipids, which are concentrated at the poles, increase the retention of MinD and MinE and explain its dwell time at this region of bacterial cells. These studies provide insight into interactions between MinD and MinE and between these proteins and membranes that are relevant to understanding the process of bacterial cell division, in which the interaction of proteins and membranes is essential.
Collapse
Affiliation(s)
- Lars D Renner
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | | |
Collapse
|
75
|
Jamroškovič J, Pavlendová N, Muchová K, Wilkinson AJ, Barák I. An oscillating Min system in Bacillus subtilis influences asymmetrical septation during sporulation. MICROBIOLOGY-SGM 2012; 158:1972-1981. [PMID: 22628484 PMCID: PMC3542138 DOI: 10.1099/mic.0.059295-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Min system plays an important role in ensuring that cell division occurs at mid-cell in rod-shaped bacteria. In Escherichia coli, pole-to-pole oscillation of the Min proteins specifically inhibits polar septation. This system also prevents polar division in Bacillus subtilis during vegetative growth; however, the Min proteins do not oscillate in this organism. The Min system of B. subtilis plays a distinct role during sporulation, a process of differentiation which begins with an asymmetrical cell division. Here, we show that oscillation of the E. coli Min proteins can be reproduced following their introduction into B. subtilis cells. Further, we present evidence that the oscillatory behaviour of the Min system inhibits sporulation. We propose that an alternative Min system mechanism avoiding oscillation is evolutionarily important because oscillation of the Min system is incompatible with efficient asymmetrical septum formation and sporulation.
Collapse
Affiliation(s)
- Ján Jamroškovič
- Institute of Molecular Biology, Slovak Academy of Sciences Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Nad'a Pavlendová
- Institute of Molecular Biology, Slovak Academy of Sciences Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Katarína Muchová
- Institute of Molecular Biology, Slovak Academy of Sciences Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| | - Anthony J Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5YW, UK
| | - Imrich Barák
- Institute of Molecular Biology, Slovak Academy of Sciences Dúbravská cesta 21, 845 51 Bratislava, Slovakia
| |
Collapse
|
76
|
Perez-Cheeks BA, Planet PJ, Sarkar IN, Clock SA, Xu Q, Figurski DH. The product of tadZ, a new member of the parA/minD superfamily, localizes to a pole in Aggregatibacter actinomycetemcomitans. Mol Microbiol 2012; 83:694-711. [PMID: 22239271 DOI: 10.1111/j.1365-2958.2011.07955.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Aggregatibacter actinomycetemcomitans establishes a tenacious biofilm that is important for periodontal disease. The tad locus encodes the components for the secretion and biogenesis of Flp pili, which are necessary for the biofilm to form. TadZ is required, but its function has been elusive. We show that tadZ genes belong to the parA/minD superfamily of genes and that TadZ from A. actinomycetemcomitans (AaTadZ) forms a polar focus in the cell independent of any other tad locus protein. Mutations indicate that regions in AaTadZ are required for polar localization and biofilm formation. We show that AaTadZ dimerizes and that all TadZ proteins are predicted to have a Walker-like A box. However, they all lack the conserved lysine at position 6 (K6) present in the canonical Walker-like A box. When the alanine residue (A6) in the atypical Walker-like A box of AaTadZ was converted to lysine, the mutant protein remained able to dimerize and localize, but it was unable to allow the formation of a biofilm. Another essential biofilm protein, the ATPase (AaTadA), also localizes to a pole. However, its correct localization depends on the presence of AaTadZ. We suggest that the TadZ proteins mediate polar localization of the Tad secretion apparatus.
Collapse
Affiliation(s)
- Brenda A Perez-Cheeks
- Department of Microbiology & Immunology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA
| | | | | | | | | | | |
Collapse
|
77
|
Cytrynbaum EN, Li YD, Allard JF, Mehrabian H. Estimating the bending modulus of a FtsZ bacterial-division protein filament. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:011902. [PMID: 22400586 DOI: 10.1103/physreve.85.011902] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 12/08/2011] [Indexed: 05/31/2023]
Abstract
FtsZ, a cytoskeletal protein homologous to tubulin, is the principle constituent of the division ring in bacterial cells. It is known to have force-generating capacity in vitro and has been conjectured to be the source of the constriction force in vivo. Several models have been proposed to explain the generation of force by the Z ring. Here we re-examine data from in vitro experiments in which Z rings formed and constricted inside tubular liposomes, and we carry out image analysis on previously published data with which to better estimate important model parameters that have proven difficult to measure by direct means. We introduce a membrane-energy-based model for the dynamics of multiple Z rings moving and colliding inside a tubular liposome and a fluid model for the drag of a Z ring as it moves through the tube. Using this model, we estimate an effective membrane bending modulus of 500-700 pN nm. If we assume that FtsZ force generation is driven by hydrolysis into a highly curved conformation, we estimate the FtsZ filament bending modulus to be 310-390 pN nm(2). If we assume instead that force is generated by the non-hydrolysis-dependent intermediate curvature conformation, we find that B(f)>1400 pN nm(2). The former value sits at the lower end of the range of previously estimated values and, if correct, may raise challenges for models that rely on filament bending to generate force.
Collapse
Affiliation(s)
- Eric N Cytrynbaum
- Department of Mathematics, University of British Columbia, Vancouver, British Columbia V6T 1Z2, Canada.
| | | | | | | |
Collapse
|
78
|
Mazor S, Vanounou S, Fishov I. Pyrene as a membrane depth gauge: Wavelength selective fluorescence approach to monitor pyrene localizations in the membrane. Chem Phys Lipids 2012; 165:125-31. [DOI: 10.1016/j.chemphyslip.2011.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 11/14/2011] [Accepted: 11/15/2011] [Indexed: 11/30/2022]
|
79
|
Balaban M, Hendrixson DR. Polar flagellar biosynthesis and a regulator of flagellar number influence spatial parameters of cell division in Campylobacter jejuni. PLoS Pathog 2011; 7:e1002420. [PMID: 22144902 PMCID: PMC3228812 DOI: 10.1371/journal.ppat.1002420] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 10/20/2011] [Indexed: 01/15/2023] Open
Abstract
Spatial and numerical regulation of flagellar biosynthesis results in different flagellation patterns specific for each bacterial species. Campylobacter jejuni produces amphitrichous (bipolar) flagella to result in a single flagellum at both poles. These flagella confer swimming motility and a distinctive darting motility necessary for infection of humans to cause diarrheal disease and animals to promote commensalism. In addition to flagellation, symmetrical cell division is spatially regulated so that the divisome forms near the cellular midpoint. We have identified an unprecedented system for spatially regulating cell division in C. jejuni composed by FlhG, a regulator of flagellar number in polar flagellates, and components of amphitrichous flagella. Similar to its role in other polarly-flagellated bacteria, we found that FlhG regulates flagellar biosynthesis to limit poles of C. jejuni to one flagellum. Furthermore, we discovered that FlhG negatively influences the ability of FtsZ to initiate cell division. Through analysis of specific flagellar mutants, we discovered that components of the motor and switch complex of amphitrichous flagella are required with FlhG to specifically inhibit division at poles. Without FlhG or specific motor and switch complex proteins, cell division occurs more often at polar regions to form minicells. Our findings suggest a new understanding for the biological requirement of the amphitrichous flagellation pattern in bacteria that extend beyond motility, virulence, and colonization. We propose that amphitrichous bacteria such as Campylobacter species advantageously exploit placement of flagella at both poles to spatially regulate an FlhG-dependent mechanism to inhibit polar cell division, thereby encouraging symmetrical cell division to generate the greatest number of viable offspring. Furthermore, we found that other polarly-flagellated bacteria produce FlhG proteins that influence cell division, suggesting that FlhG and polar flagella may function together in a broad range of bacteria to spatially regulate division. Campylobacter jejuni is a leading cause of gastroenteritis in humans and requires amphitrichous (bipolar) flagella to promote infection of hosts. This pattern of flagellation results in a single flagellum at both poles, which is characteristic of many Campylobacter species, but fairly unusual amongst other motile bacteria. In this work, we discovered an unprecedented system to spatially regulate cell division that relies on the FlhG ATPase and amphitrichous flagellar biosynthesis. In addition to its role in other polar flagellates in controlling flagellar number, we discovered that FlhG influences spatial regulation of cell division in C. jejuni. Further analysis revealed that components of the flagellar motor and switch are required with FlhG to inhibit cell division specifically at the poles of the bacterium. These findings indicate that flagella have an additional function in C. jejuni beyond promoting motility, virulence, and colonization in functioning in a mechanism with FlhG to inhibit cell division specifically at poles. Furthermore, our findings suggest that the specific amphitrichous pattern of flagellar biosynthesis in this pathogen is an essential determinant for inhibiting cell division at both bacterial poles so that symmetrical cell division occurs and generates viable progenitors.
Collapse
Affiliation(s)
- Murat Balaban
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - David R. Hendrixson
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
| |
Collapse
|
80
|
Abstract
One of the most fundamental features of biological systems is probably their ability to self-organize in space and time on different scales. Despite many elaborate theoretical models of how molecular self-organization can come about, only a few experimental systems of biological origin have so far been rigorously described, due mostly to their inherent complexity. The most promising strategy of modern biophysics is thus to identify minimal biological systems showing self-organized emergent behavior. One of the best-understood examples of protein self-organization, which has recently been successfully reconstituted in vitro, is represented by the oscillations of the Min proteins in Escherichia coli. In this review, we summarize the current understanding of the mechanism of Min protein self-organization in vivo and in vitro. We discuss the potential of the Min oscillations to sense the geometry of the cell and suggest that spontaneous protein waves could be a general means of intracellular organization. We hypothesize that cooperative membrane binding and unbinding, e.g., as an energy-dependent switch, may act as an important regulatory mechanism for protein oscillations and pattern formation in the cell.
Collapse
Affiliation(s)
- Martin Loose
- Biophysics, BIOTEC, Dresden University of Technology, Dresden, Germany.
| | | | | |
Collapse
|
81
|
Park KT, Wu W, Battaile KP, Lovell S, Holyoak T, Lutkenhaus J. The Min oscillator uses MinD-dependent conformational changes in MinE to spatially regulate cytokinesis. Cell 2011; 146:396-407. [PMID: 21816275 PMCID: PMC3155264 DOI: 10.1016/j.cell.2011.06.042] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/23/2011] [Accepted: 06/24/2011] [Indexed: 10/17/2022]
Abstract
In E. coli, MinD recruits MinE to the membrane, leading to a coupled oscillation required for spatial regulation of the cytokinetic Z ring. How these proteins interact, however, is not clear because the MinD-binding regions of MinE are sequestered within a six-stranded β sheet and masked by N-terminal helices. minE mutations that restore interaction between some MinD and MinE mutants were isolated. These mutations alter the MinE structure leading to release of the MinD-binding regions and the N-terminal helices that bind the membrane. Crystallization of MinD-MinE complexes revealed a four-stranded β sheet MinE dimer with the released β strands (MinD-binding regions) converted to α helices bound to MinD dimers. These results identify the MinD-dependent conformational changes in MinE that convert it from a latent to an active form and lead to a model of how MinE persists at the MinD-membrane surface.
Collapse
Affiliation(s)
- Kyung-Tae Park
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City KS 66160
| | - Wei Wu
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City KS 66160
| | - Kevin P. Battaile
- IMCA-CAT, Hauptman-Woodward Medical Research Institute, Sector 17, APS Argonne National Laboratory 9700 S. Cass Avenue, Bldg. 435A, Argonne, IL 60439 USA
| | - Scott Lovell
- Structural Biology Center, University of Kansas, 2121 Simons Drive, Lawrence, KS 66047
| | - Todd Holyoak
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City KS 66160
| | - Joe Lutkenhaus
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City KS 66160
| |
Collapse
|
82
|
Stjepanovic G, Kapp K, Bange G, Graf C, Parlitz R, Wild K, Mayer MP, Sinning I. Lipids trigger a conformational switch that regulates signal recognition particle (SRP)-mediated protein targeting. J Biol Chem 2011; 286:23489-97. [PMID: 21543314 DOI: 10.1074/jbc.m110.212340] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Co-translational protein targeting to the membrane is mediated by the signal recognition particle and its receptor (FtsY). Their homologous GTPase domains interact at the membrane and form a heterodimer in which both GTPases are activated. The prerequisite for protein targeting is the interaction of FtsY with phospholipids. However, the mechanism of FtsY regulation by phospholipids remained unclear. Here we show that the N terminus of FtsY (A domain) is natively unfolded in solution and define the complete membrane-targeting sequence. We show that the membrane-targeting sequence is highly dynamic in solution, independent of nucleotides and directly responds to the density of anionic phospholipids by a random coil-helix transition. This conformational switch is essential for tethering FtsY to membranes and activates the GTPase for its subsequent interaction with the signal recognition particle. Our results underline the dynamics of lipid-protein interactions and their importance in the regulation of protein targeting and translocation across biological membranes.
Collapse
Affiliation(s)
- Goran Stjepanovic
- Biochemie Zentrum (BZH), University of Heidelberg, INF 328, 69120 Heidelberg, Germany
| | | | | | | | | | | | | | | |
Collapse
|
83
|
Renner LD, Weibel DB. Cardiolipin microdomains localize to negatively curved regions of Escherichia coli membranes. Proc Natl Acad Sci U S A 2011; 108:6264-9. [PMID: 21444798 PMCID: PMC3076878 DOI: 10.1073/pnas.1015757108] [Citation(s) in RCA: 264] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many proteins reside at the cell poles in rod-shaped bacteria. Several hypotheses have drawn a connection between protein localization and the large cell-wall curvature at the poles. One hypothesis has centered on the formation of microdomains of the lipid cardiolipin (CL), its localization to regions of high membrane curvature, and its interaction with membrane-associated proteins. A lack of experimental techniques has left this hypothesis unanswered. This paper describes a microtechnology-based technique for manipulating bacterial membrane curvature and quantitatively measuring its effect on the localization of CL and proteins in cells. We confined Escherichia coli spheroplasts in microchambers with defined shapes that were embossed into a layer of polymer and observed that the shape of the membrane deformed predictably to accommodate the walls of the microchambers. Combining this technique with epifluorescence microscopy and quantitative image analyses, we characterized the localization of CL microdomains in response to E. coli membrane curvature. CL microdomains localized to regions of high intrinsic negative curvature imposed by microchambers. We expressed a chimera of yellow fluorescent protein fused to the N-terminal region of MinD--a spatial determinant of E. coli division plane assembly--in spheroplasts and observed its colocalization with CL to regions of large, negative membrane curvature. Interestingly, the distribution of MinD was similar in spheroplasts derived from a CL synthase knockout strain. These studies demonstrate the curvature dependence of CL in membranes and test whether these structures participate in the localization of MinD to regions of negative curvature in cells.
Collapse
Affiliation(s)
| | - Douglas B. Weibel
- Departments of Biochemistry and
- Biomedical Engineering, University of Wisconsin, Madison, WI 53706
| |
Collapse
|
84
|
Okuno T, Ohgita T, Sasa T, Nonaka A, Funasaki N, Kogure K. Fluorescence polarization analysis for revealing molecular mechanism of nucleotide-dependent phospholipid membrane binding of MinD adenosine 5'-triphosphate, adenosine triphosphatase. Biol Pharm Bull 2011; 33:1746-50. [PMID: 20930386 DOI: 10.1248/bpb.33.1746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Membrane binding of Walker type adenosine 5'-triphosphate, adenosine triphosphatase (ATPase), MinD, is a key step in regulating the site of cell division in Escherichia coli. Two lysine residues (K11, K16) in the Walker A motif of MinD have been suggested to be essential for both membrane binding and ATPase activity, but the relationship between the membrane binding of MinD and its ATPase activity is still unclear. To reveal the role of K11 and K16 in MinD membrane interaction and ATP-binding, we compared the functionality of wild-type MinD (WT) and two MinD mutants that lack ATPase activity, where alanine was substituted for lysine at positions 11 and 16 (K11A, K16A), using liposomes and fluorescent-labeled ATP. The ATP dissociation constant (K(d)) of wild-type MinD was 4.9 µM. Unexpectedly, the K(d) values of the two lysine mutants were almost the same as that of wild type, indicating that ATP can bind to MinD mutants, even though these mutants showed no ATPase activity and membrane binding ability. Our results presumed that K11 and K16 residues might play an important role in dimmer formation of MinD, but not ATP binding step, for recruiting to membrane.
Collapse
Affiliation(s)
- Takashi Okuno
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Japan.
| | | | | | | | | | | |
Collapse
|
85
|
Wu W, Park KT, Holyoak T, Lutkenhaus J. Determination of the structure of the MinD-ATP complex reveals the orientation of MinD on the membrane and the relative location of the binding sites for MinE and MinC. Mol Microbiol 2011; 79:1515-28. [PMID: 21231967 DOI: 10.1111/j.1365-2958.2010.07536.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The three Min proteins spatially regulate Z ring positioning in Escherichia coli and are dynamically associated with the membrane. MinD binds to vesicles in the presence of ATP and can recruit MinC or MinE. Biochemical and genetic evidence indicate the binding sites for these two proteins on MinD overlap. Here we solved the structure of a hydrolytic-deficient mutant of MinD truncated for the C-terminal amphipathic helix involved in binding to the membrane. The structure solved in the presence of ATP is a dimer and reveals the face of MinD abutting the membrane. Using a combination of random and extensive site-directed mutagenesis additional residues important for MinE and MinC binding were identified. The location of these residues on the MinD structure confirms that the binding sites overlap and reveals that the binding sites are at the dimer interface and exposed to the cytosol. The location of the binding sites at the dimer interface offers a simple explanation for the ATP dependence of MinC and MinE binding to MinD.
Collapse
Affiliation(s)
- Wei Wu
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | | | | | | |
Collapse
|
86
|
Bowman GR, Lyuksyutova AI, Shapiro L. Bacterial polarity. Curr Opin Cell Biol 2010; 23:71-7. [PMID: 21095111 DOI: 10.1016/j.ceb.2010.10.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 10/20/2010] [Accepted: 10/30/2010] [Indexed: 01/05/2023]
Abstract
Many recent studies have revealed exquisite subcellular localization of proteins, DNA, and other molecules within bacterial cells, giving credence to the concept of prokaryotic anatomy. Common sites for localized components are the poles of rod-shaped cells, which are dynamically modified in composition and function in order to control cellular physiology. An impressively diverse array of mechanisms underlies bacterial polarity, including oscillatory systems, phospho-signaling pathways, the sensing of membrane curvature, and the integration of cell cycle regulators with polar maturation.
Collapse
Affiliation(s)
- Grant R Bowman
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | | | | |
Collapse
|
87
|
Differences in MinC/MinD sensitivity between polar and internal Z rings in Escherichia coli. J Bacteriol 2010; 193:367-76. [PMID: 21097625 DOI: 10.1128/jb.01095-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In Escherichia coli the Z ring has the potential to assemble anywhere along the cell length but is restricted to midcell by the action of negative regulatory systems, including Min. In the current model for the Min system, the MinC/MinD division inhibitory complex is evenly distributed on the membrane and can disrupt Z rings anywhere in the cell; however, MinE spatially regulates MinC/MinD by restricting it to the cell poles, thus allowing Z ring formation at midcell. This model assumes that Z rings formed at different cellular locations have equal sensitivity to MinC/MinD in the absence of MinE. However, here we report evidence that differences in MinC/MinD sensitivity between polar and nonpolar Z rings exists even when there is no MinE. MinC/MinD at proper levels is able to block minicell production in Δmin strains without increasing the cell length, indicating that polar Z rings are preferentially blocked. In the FtsZ-I374V strain (which is resistant to MinC(C)/MinD), wild-type morphology can be easily achieved with MinC/MinD in the absence of MinE. We also show that MinC/MinD at proper levels can rescue the lethal phenotype of a min slmA double deletion mutant, which we think is due to the elimination of polar Z rings (or FtsZ structures), which frees up FtsZ molecules for assembly of Z rings at internal sites to rescue division and growth. Taken together, these data indicate that polar Z rings are more susceptible to MinC/MinD than internal Z rings, even when MinE is absent.
Collapse
|
88
|
Arumugam S, Chwastek G, Schwille P. Protein-membrane interactions: the virtue of minimal systems in systems biology. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2010; 3:269-80. [PMID: 20865776 DOI: 10.1002/wsbm.119] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The plasma membrane of cells can be viewed as a highly dynamic, regulated, heterogeneous environment with multiple functions. It constitutes the boundary of the cell, encapsulating all its components. Proteins interact with the membrane in many ways to accommodate essential processes, such as membrane trafficking, membrane protrusions, cytokinesis, signaling, and cell-cell communication. A vast amount of literature has already fostered our current understanding of membrane-protein interactions. However, many phenomena still remain to be understood, e.g., the exact mechanisms of how certain proteins cause or assist membrane transformations. Systems biology aims to predict biological processes on the basis of the set of molecules involved. Many key processes arise from interactions with the lipid membrane. Protein interactome maps do not consider such specific interactions, and thus cannot predict precise outcomes of the interactions of the involved proteins. These can only be inferred from experimental approaches. We describe examples of how an emergent behavior of protein-membrane interactions has been demonstrated by the use of minimal systems. These studies contribute to a deeper understanding of protein interactomes involving membranes and complement other approaches of systems biology.
Collapse
|
89
|
Bibi E. Early targeting events during membrane protein biogenesis in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:841-50. [PMID: 20682283 DOI: 10.1016/j.bbamem.2010.07.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 07/21/2010] [Accepted: 07/22/2010] [Indexed: 10/19/2022]
Abstract
All living cells have co-translational pathways for targeting membrane proteins. Co-translation pathways for secretory proteins also exist but mostly in eukaryotes. Unlike secretory proteins, the biosynthetic pathway of most membrane proteins is conserved through evolution and these proteins are usually synthesized by membrane-bound ribosomes. Translation on the membrane requires that both the ribosomes and the mRNAs be properly localized. Theoretically, this can be achieved by several means. (i) The current view is that the targeting of cytosolic mRNA-ribosome-nascent chain complexes (RNCs) to the membrane is initiated by information in the emerging hydrophobic nascent polypeptides. (ii) The alternative model suggests that ribosomes may be targeted to the membrane also constitutively, whereas the appropriate mRNAs may be carried on small ribosomal subunits or targeted by other cellular factors to the membrane-bound ribosomes. Importantly, the available experimental data do not rule out the possibility that cells may also utilize both pathways in parallel. In any case, it is well documented that a major player in the targeting pathway is the signal recognition particle (SRP) system composed of the SRP and its receptor (SR). Although the functional core of the SRP system is evolutionarily conserved, its composition and biological practice come with different flavors in various organisms. This review is dedicated mainly to the Escherichia (E.) coli SRP, where the biochemical and structural properties of components of the SRP system have been relatively characterized, yielding essential information about various aspects of the pathway. In addition, several cellular interactions of the SRP and its receptor have been described in E. coli, providing insights into their spatial function. Collectively, these in vitro studies have led to the current view of the targeting pathway [see (i) above]. Interestingly, however, in vivo studies of the role of the SRP and its receptor, with emphasis on the temporal progress of the pathway, elicited an alternative hypothesis [see (ii) above]. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
Collapse
Affiliation(s)
- Eitan Bibi
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
| |
Collapse
|
90
|
Abstract
Many cell division-related proteins are located at specific positions in the bacterial cell, and this organized distribution of proteins requires energy. Here, we report that the proton motive force, or more specifically the (trans)membrane potential, is directly involved in protein localization. It emerged that the membrane potential modulates the distribution of several conserved cell division proteins such as MinD, FtsA, and the bacterial cytoskeletal protein MreB. We show for MinD that this is based on the membrane potential stimulated binding of its C-terminal amphipathic helix. This function of the membrane potential has implications for how these morphogenetic proteins work and provide an explanation for the effects observed with certain antimicrobial compounds.
Collapse
|
91
|
Abstract
The Min system regulates the positioning of the cell division site in many bacteria. In Escherichia coli, MinD migrates rapidly from one cell pole to the other. In conjunction with MinC, MinD helps to prevent unwanted FtsZ rings from assembling at the poles and to stabilize their positioning at midcell. Using time-lapse microscopy of growing and dividing cells expressing a gfp-minD fusion, we show that green fluorescent protein (GFP)-MinD often paused at midcell in addition to at the poles, and the frequency of midcell pausing increased as cells grew longer and cell division approached. At later stages of septum formation, GFP-MinD often paused specifically on only one side of the septum, followed by migration to the other side of the septum or to a cell pole. About the time of septum closure, this irregular pattern often switched to a transient double pole-to-pole oscillation in the daughter cells, which ultimately became a stable double oscillation. The splitting of a single MinD zone into two depends on the developing septum and is a potential mechanism to explain how MinD is distributed equitably to both daughter cells. Septal pausing of GFP-MinD did not require MinC, suggesting that MinC-FtsZ interactions do not drive MinD-septal interactions, and instead MinD recognizes a specific geometric, lipid, and/or protein target at the developing septum. Finally, we observed regular end-to-end oscillation over very short distances along the long axes of minicells, supporting the importance of geometry in MinD localization.
Collapse
|
92
|
Abstract
Understanding the mechanisms that underlie the organization of bacterial cells has become a significant challenge in the field of bacterial cytology. Of specific interest are early macromolecular sorting events that establish cellular non-uniformity and provide chemical landmarks for later localization events. In this review, we will examine specific examples of lipids and proteins that appear to exploit differences in membrane curvature to drive their localization to particular regions of a bacterial cell. We will also discuss the physical limits of curvature-mediated localization within bacteria, and the use of modelling to infer biophysical properties of curvature-sensing macromolecules.
Collapse
Affiliation(s)
- Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.
| | | |
Collapse
|
93
|
Abstract
We have developed a system for producing tubular multilamellar liposomes that incorporate the protein FtsZ on the inside. We start with a mixture of spherical multilamellar liposomes with FtsZ initially on the outside. Shearing forces generated by applying a coverslip most likely distort some of the spherical liposomes into a tubular shape, and causes some to leak and incorporate FtsZ inside. We describe protocols for liposome preparation, and for preparing membrane-targeted FtsZ that can assemble contractile Z rings inside the tubular liposomes. We also describe the characterization of the multilamellar liposomes in terms of the permeability or leakiness for a small fluorescent dye and larger protein molecules. These liposomes may be useful for reconstitution of other biological systems.
Collapse
|
94
|
Division site selection in rod-shaped bacteria. Curr Opin Microbiol 2009; 12:683-8. [PMID: 19884039 DOI: 10.1016/j.mib.2009.10.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/28/2009] [Accepted: 10/01/2009] [Indexed: 11/22/2022]
Abstract
Rod-shaped bacteria often divide with high precision at midcell to produce two equally sized daughter cells. The positioning of the division machinery in Escherichia coli and Bacillus subtilis is spatially regulated by two inhibitory systems, the nucleoid occlusion and the Min system. The current models suggest that the target of the inhibitory mechanism is the cytoskeletal element FtsZ and that the concerted action of nucleoid occlusion and Min are necessary for correct placement of the division machinery. However, recent advances show that at least the Min system also ensures that division occurs only once in a cell cycle and might also act downstream of FtsZ assembly.
Collapse
|
95
|
Drin G, Antonny B. Amphipathic helices and membrane curvature. FEBS Lett 2009; 584:1840-7. [PMID: 19837069 DOI: 10.1016/j.febslet.2009.10.022] [Citation(s) in RCA: 412] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 10/09/2009] [Indexed: 01/29/2023]
Abstract
Numerous data have been collected on lipid-binding amphipathic helices involved in membrane-remodeling machineries and vesicular transport. Here we describe how, with regard to lipid composition, the physicochemical features of some amphipathic helices explain their ability to recognize membrane curvature or to participate in membrane remodeling. We propose that sensing highly-curved membranes requires that the polar and hydrophobic faces of the helix do not cooperate in lipid binding. A more detailed description of the interaction between amphipathic helices and lipids is however needed; notably to explain how new helices contribute to detection of modest changes in curvature or even negative curvature.
Collapse
Affiliation(s)
- Guillaume Drin
- Université de Nice-Sophia Antipolis and CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France.
| | | |
Collapse
|
96
|
Vats P, Yu J, Rothfield L. The dynamic nature of the bacterial cytoskeleton. Cell Mol Life Sci 2009; 66:3353-62. [PMID: 19641848 PMCID: PMC2810845 DOI: 10.1007/s00018-009-0092-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 05/27/2009] [Accepted: 07/03/2009] [Indexed: 10/20/2022]
Abstract
Three of the four well-established bacterial cytoskeletal systems-the MreB, MinCDE, and FtsZ systems-undergo a variety of short-range and long-range dynamic behaviors. These include the cellular reorganization of the cytoskeletal elements, in which the proteins redistribute from a predominantly helical pole-to-pole pattern into annular structures near midcell. Despite their apparent similarity, these dramatic redistributional events in the three systems are in large part independent of each other. In addition, some of the cytoskeletal structures undergo oscillatory behavior in which the helical elements move repetitively back-and-forth between the two ends of the cell. The details and mechanisms underlying these dynamic cellular events are just now being revealed by fluorescence microscopy of intact cells, fluorescence photobleaching recovery studies, single molecule tracking techniques, and in vitro studies of the purified proteins.
Collapse
Affiliation(s)
- Purva Vats
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
| | | | | |
Collapse
|
97
|
Curved FtsZ protofilaments generate bending forces on liposome membranes. EMBO J 2009; 28:3476-84. [PMID: 19779463 DOI: 10.1038/emboj.2009.277] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Accepted: 08/18/2009] [Indexed: 11/09/2022] Open
Abstract
We have created FtsZ-YFP-mts where an amphipathic helix on the C-terminus tethers FtsZ to the membrane. When incorporated inside multi-lamellar tubular liposomes, FtsZ-YFP-mts can assemble Z rings that generate a constriction force. When added to the outside of liposomes, FtsZ-YFP-mts bound and produced concave depressions, bending the membrane in the same direction as the Z ring inside liposomes. Prominent membrane tubules were then extruded at the intersections of concave depressions. We tested the effect of moving the membrane-targeting sequence (mts) from the C-terminus to the N-terminus, which is approximately 180 degrees from the C-terminal tether. When mts-FtsZ-YFP was applied to the outside of liposomes, it generated convex bulges, bending the membrane in the direction opposite to the concave depressions. We conclude that FtsZ protofilaments have a fixed direction of curvature, and the direction of membrane bending depends on which side of the bent protofilament the mts is attached to. This supports models in which the FtsZ constriction force is generated by protofilament bending.
Collapse
|
98
|
Abstract
Simple visual inspection of bacteria indicated that, at least in some otherwise symmetric cells, structures such as flagella were often seen at a single pole. Because these structures are composed of proteins, it was not clear how to reconcile these observations of morphological asymmetry with the widely held view of bacteria as unstructured "bags of enzymes." However, over the last decade, numerous GFP tagged proteins have been found at specific intracellular locations such as the poles of the cells, indicating that bacteria have a high degree of intracellular organization. Here we will explore the role of chromosomal asymmetry and the presence of "new" and "old" poles that result from the cytokinesis of rod-shaped cells in establishing bipolar and monopolar protein localization patterns. This article is intended to be illustrative, not exhaustive, so we have focused on examples drawn largely from Caulobacter crescentus and Bacillus subtilis, two bacteria that undergo dramatic morphological transformation. We will highlight how breaking monopolar symmetry is essential for the correct development of these organisms.
Collapse
Affiliation(s)
- Jonathan Dworkin
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York 10032, USA.
| |
Collapse
|
99
|
Lenarcic R, Halbedel S, Visser L, Shaw M, Wu LJ, Errington J, Marenduzzo D, Hamoen LW. Localisation of DivIVA by targeting to negatively curved membranes. EMBO J 2009; 28:2272-82. [PMID: 19478798 PMCID: PMC2690451 DOI: 10.1038/emboj.2009.129] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 04/15/2009] [Indexed: 11/22/2022] Open
Abstract
DivIVA is a conserved protein in Gram-positive bacteria and involved in various processes related to cell growth, cell division and spore formation. DivIVA is specifically targeted to cell division sites and cell poles. In Bacillus subtilis, DivIVA helps to localise other proteins, such as the conserved cell division inhibitor proteins, MinC/MinD, and the chromosome segregation protein, RacA. Little is known about the mechanism that localises DivIVA. Here we show that DivIVA binds to liposomes, and that the N terminus harbours the membrane targeting sequence. The purified protein can stimulate binding of RacA to membranes. In mutants with aberrant cell shapes, DivIVA accumulates where the cell membrane is most strongly curved. On the basis of electron microscopic studies and other data, we propose that this is due to molecular bridging of the curvature by DivIVA multimers. This model may explain why DivIVA localises at cell division sites. A Monte-Carlo simulation study showed that molecular bridging can be a general mechanism for binding of proteins to negatively curved membranes.
Collapse
Affiliation(s)
- Rok Lenarcic
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
| | | | | | | | | | | | | | | |
Collapse
|
100
|
Braig D, Bär C, Thumfart JO, Koch HG. Two cooperating helices constitute the lipid-binding domain of the bacterial SRP receptor. J Mol Biol 2009; 390:401-13. [PMID: 19414018 DOI: 10.1016/j.jmb.2009.04.061] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 04/02/2009] [Accepted: 04/28/2009] [Indexed: 11/19/2022]
Abstract
Protein targeting by the bacterial signal recognition particle requires the specific interaction of the signal recognition particle (SRP)-ribosome-nascent chain complex with FtsY, the bacterial SRP receptor. Although FtsY in Escherichia coli lacks a transmembrane domain, the membrane-bound FtsY displays many features of an integral membrane protein. Our data reveal that it is the cooperative action of two lipid-binding helices that allows this unusually strong membrane contact. Helix I comprises the first 14 amino acids of FtsY and the second is located at the interface between the A- and the N-domain of FtsY. We show by site-directed cross-linking and binding assays that both helices bind to negatively charged phospholipids, with a preference for phosphatidyl glycerol. Despite the strong lipid binding, helix I does not seem to be completely inserted into the lipid phase, but appears to be oriented parallel with the membrane surface. The two helices together with the connecting linker constitute an independently folded domain, which maintains its lipid binding even in the absence of the conserved NG-core of FtsY. In summary, our data reveal that the two consecutive lipid-binding helices of FtsY can provide a membrane contact that does not differ significantly in stability from that provided by a transmembrane domain. This explains why the bacterial SRP receptor does not require an integral beta-subunit for membrane binding.
Collapse
Affiliation(s)
- David Braig
- Institut für Biochemie und Molekularbiologie, ZBMZ, Albert-Ludwigs-Universität Freiburg, Germany
| | | | | | | |
Collapse
|