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Abstract
Diffusion within bacteria is often thought of as a "simple" random process by which molecules collide and interact with each other. New research however shows that this is far from the truth. Here we shed light on the complexity and importance of diffusion in bacteria, illustrating the similarities and differences of diffusive behaviors of molecules within different compartments of bacterial cells. We first describe common methodologies used to probe diffusion and the associated models and analyses. We then discuss distinct diffusive behaviors of molecules within different bacterial cellular compartments, highlighting the influence of metabolism, size, crowding, charge, binding, and more. We also explicitly discuss where further research and a united understanding of what dictates diffusive behaviors across the different compartments of the cell are required, pointing out new research avenues to pursue.
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Affiliation(s)
- Christopher H Bohrer
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA.
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA.
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA.
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2
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Sochacki KA, Shkel IA, Record MT, Weisshaar JC. Protein diffusion in the periplasm of E. coli under osmotic stress. Biophys J 2011; 100:22-31. [PMID: 21190653 DOI: 10.1016/j.bpj.2010.11.044] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 11/10/2010] [Accepted: 11/16/2010] [Indexed: 11/17/2022] Open
Abstract
The physical and mechanical properties of the cell envelope of Escherichia coli are poorly understood. We use fluorescence recovery after photobleaching to measure diffusion of periplasmic green fluorescent protein and probe the fluidity of the periplasm as a function of external osmotic conditions. For cells adapted to growth in complete medium at 0.14-1.02 Osm, the mean diffusion coefficient <D(peri)> increases from 3.4 μm² s⁻¹ to 6.6 μm² s⁻¹ and the distribution of D(peri) broadens as growth osmolality increases. This is consistent with a net gain of water by the periplasm, decreasing its biopolymer volume fraction. This supports a model in which the turgor pressure drops primarily across the thin peptidoglycan layer while the cell actively maintains osmotic balance between periplasm and cytoplasm, thus avoiding a substantial pressure differential across the cytoplasmic membrane. After sudden hyperosmotic shock (plasmolysis), the cytoplasm loses water as the periplasm gains water. Accordingly, <D(peri)> increases threefold. The fluorescence recovery after photobleaching is complete and homogeneous in all cases, but in minimal medium, the periplasm is evidently thicker at the cell tips. For the relevant geometries, Brownian dynamics simulations in model cytoplasmic and periplasmic volumes provide analytical formulae for extraction of accurate diffusion coefficients from readily measurable quantities.
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Affiliation(s)
- Kem A Sochacki
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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3
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Den Blaauwen T, de Pedro MA, Nguyen-Distèche M, Ayala JA. Morphogenesis of rod-shaped sacculi. FEMS Microbiol Rev 2008; 32:321-44. [DOI: 10.1111/j.1574-6976.2007.00090.x] [Citation(s) in RCA: 235] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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4
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Mariscal V, Herrero A, Flores E. Continuous periplasm in a filamentous, heterocyst-forming cyanobacterium. Mol Microbiol 2007; 65:1139-45. [PMID: 17645442 DOI: 10.1111/j.1365-2958.2007.05856.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cyanobacteria bear a Gram-negative type of cell wall that includes a peptidoglycan layer and an outer membrane outside of the cytoplasmic membrane. In filamentous cyanobacteria, the outer membrane appears to be continuous along the filament of cells. In the heterocyst-forming cyanobacteria, two cell types contribute specialized functions for growth: vegetative cells provide reduced carbon to heterocysts, which provide N2-derived fixed nitrogen to vegetative cells. The promoter of the patS gene, which is active specifically in developing proheterocysts and heterocysts of Anabaena sp. PCC 7120, was used to direct the expression of altered versions of the gfp gene. An engineered green fluorescent protein (GFP) that was exported to the periplasm of the proheterocysts through the twin-arginine translocation system was observed also in the periphery of neighbouring vegetative cells. However, if the GFP was anchored to the cytoplasmic membrane, it was observed in the periphery of the producing proheterocysts or heterocysts but not in adjacent vegetative cells. These results show that there is no cytoplasmic membrane continuity between heterocysts and vegetative cells and that the GFP protein can move along the filament in the periplasm, which is functionally continuous and so provides a conduit that can be used for chemical communication between cells.
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Affiliation(s)
- Vicente Mariscal
- Instituto de Bioquímica Vegetal y Fotosíntesis, C.S.I.C. and Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain
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5
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Jenal U, Stephens C, Shapiro L. Regulation of asymmetry and polarity during the Caulobacter cell cycle. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 71:1-39. [PMID: 8644489 DOI: 10.1002/9780470123171.ch1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- U Jenal
- Department of Developmental Biology, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford University, California 94305, USA
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6
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Mullineaux CW, Nenninger A, Ray N, Robinson C. Diffusion of green fluorescent protein in three cell environments in Escherichia coli. J Bacteriol 2006; 188:3442-8. [PMID: 16672597 PMCID: PMC1482841 DOI: 10.1128/jb.188.10.3442-3448.2006] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Surprisingly little is known about the physical environment inside a prokaryotic cell. Knowledge of the rates at which proteins and other cell components can diffuse is crucial for the understanding of a cell as a physical system. There have been numerous measurements of diffusion coefficients in eukaryotic cells by using fluorescence recovery after photobleaching (FRAP) and related techniques. Much less information is available about diffusion coefficients in prokaryotic cells, which differ from eukaryotic cells in a number of significant respects. We have used FRAP to observe the diffusion of green fluorescent protein (GFP) in cells of Escherichia coli elongated by growth in the presence of cephalexin. GFP was expressed in the cytoplasm, exported into the periplasm using the twin-arginine translocation (Tat) system, or fused to an integral plasma membrane protein (TatA). We show that TatA-GFP diffuses in the plasma membrane with a diffusion coefficient comparable to that of a typical eukaryotic membrane protein. A previous report showed a very low rate of protein diffusion in the E. coli periplasm. However, we measured a GFP diffusion coefficient only slightly smaller in the periplasm than that in the cytoplasm, showing that both cell compartments are relatively fluid environments.
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Affiliation(s)
- Conrad W Mullineaux
- School of Biological and Chemical Sciences, Queen Mary, University of London, UK.
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7
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Vicente M, Rico AI, Martínez-Arteaga R, Mingorance J. Septum enlightenment: assembly of bacterial division proteins. J Bacteriol 2006; 188:19-27. [PMID: 16352817 PMCID: PMC1317574 DOI: 10.1128/jb.188.1.19-27.2006] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Miguel Vicente
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, c/ Darwin 3, 28049 Madrid, Spain.
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8
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Scheffers DJ, Pinho MG. Bacterial cell wall synthesis: new insights from localization studies. Microbiol Mol Biol Rev 2006; 69:585-607. [PMID: 16339737 PMCID: PMC1306805 DOI: 10.1128/mmbr.69.4.585-607.2005] [Citation(s) in RCA: 414] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In order to maintain shape and withstand intracellular pressure, most bacteria are surrounded by a cell wall that consists mainly of the cross-linked polymer peptidoglycan (PG). The importance of PG for the maintenance of bacterial cell shape is underscored by the fact that, for various bacteria, several mutations affecting PG synthesis are associated with cell shape defects. In recent years, the application of fluorescence microscopy to the field of PG synthesis has led to an enormous increase in data on the relationship between cell wall synthesis and bacterial cell shape. First, a novel staining method enabled the visualization of PG precursor incorporation in live cells. Second, penicillin-binding proteins (PBPs), which mediate the final stages of PG synthesis, have been localized in various model organisms by means of immunofluorescence microscopy or green fluorescent protein fusions. In this review, we integrate the knowledge on the last stages of PG synthesis obtained in previous studies with the new data available on localization of PG synthesis and PBPs, in both rod-shaped and coccoid cells. We discuss a model in which, at least for a subset of PBPs, the presence of substrate is a major factor in determining PBP localization.
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Affiliation(s)
- Dirk-Jan Scheffers
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
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Wu LJ, Errington J. Coordination of cell division and chromosome segregation by a nucleoid occlusion protein in Bacillus subtilis. Cell 2004; 117:915-25. [PMID: 15210112 DOI: 10.1016/j.cell.2004.06.002] [Citation(s) in RCA: 309] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2003] [Revised: 04/23/2004] [Accepted: 04/27/2004] [Indexed: 10/26/2022]
Abstract
A range of genetical and physiological experiments have established that diverse bacterial cells possess a function called nucleoid occlusion, which acts to prevent cell division in the vicinity of the nucleoid. We have identified a specific effector of nucleoid occlusion in Bacillus subtilis, Noc (YyaA), as an inhibitor of division that is also a nonspecific DNA binding protein. Under various conditions in which the cell cycle is perturbed, Noc prevents the division machinery from assembling in the vicinity of the nucleoid. Unexpectedly, cells lacking both Noc and the Min system (which prevents division close to the cell poles) are blocked for division, apparently because they establish multiple nonproductive accumulations of division proteins. The results help to explain how B. subtilis specifies the division site under a range of conditions and how it avoids catastrophic breakage of the chromosome by division through the nucleoid.
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Affiliation(s)
- Ling Juan Wu
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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10
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de Pedro MA, Grünfelder CG, Schwarz H. Restricted Mobility of Cell Surface Proteins in the Polar Regions of Escherichia coli. J Bacteriol 2004; 186:2594-602. [PMID: 15090499 PMCID: PMC387780 DOI: 10.1128/jb.186.9.2594-2602.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The polar regions of the Escherichia coli murein sacculus are metabolically inert and stable in time. Because the sacculus and the outer membrane are tightly associated, we investigated whether polar inert murein could restrict the mobility of other cell envelope elements. Cells were covalently labeled with a fluorescent reagent, chased in dye-free medium, and observed by microscopy. Fluorescent material was more efficiently retained at the cell poles than at any other location. The boundary between high and low fluorescence intensity areas was rather sharp. Labeled material consisted mostly of cell envelope proteins, among them the free and murein-bound forms of Braun's lipoprotein. Our results indicate that the mobility of at least some cell envelope proteins is restrained at regions in correspondence with underlying areas of inert murein.
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Affiliation(s)
- Miguel A de Pedro
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain.
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11
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Judd EM, Ryan KR, Moerner WE, Shapiro L, McAdams HH. Fluorescence bleaching reveals asymmetric compartment formation prior to cell division in Caulobacter. Proc Natl Acad Sci U S A 2003; 100:8235-40. [PMID: 12824468 PMCID: PMC166212 DOI: 10.1073/pnas.1433105100] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Asymmetric cell division in Caulobacter crescentus yields daughter cells that have different cell fates. Compartmentalization of the predivisional cell is a critical event in the establishment of the differential distribution of regulatory factors that specify cell fate. To determine when during the cell cycle the cytoplasm is compartmentalized so that cytoplasmic proteins can no longer diffuse between the two nascent progeny cell compartments, we designed a fluorescence loss in photobleaching assay. Individual cells containing enhanced GFP were exposed to a bleaching laser pulse tightly focused at one cell pole. In compartmentalized cells, fluorescence disappears only in the compartment receiving the bleaching beam; in noncompartmentalized cells, fluorescence disappears from the entire cell. In a 135-min cell cycle, the cells were compartmentalized 18 +/- 5 min before the progeny cells separated. Clearance of the 22000 CtrA master transcriptional regulator molecules from the stalked portion of the predivisional cell is a controlling element of Caulobacter asymmetry. Monitoring of a fluorescent marker for CtrA showed that the differential degradation of CtrA in the nascent stalk cell compartment occurs only after the cytoplasm is compartmentalized.
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Affiliation(s)
- Ellen M. Judd
- Department of Developmental Biology, Stanford
University School of Medicine, 300 Beckman Center, Stanford, CA 94305;
Department of Chemistry, Stanford University,
375 North-South Mall, MC 5080, Stanford, CA 94305; and
Department of Applied Physics, Stanford
University, Stanford, CA 94305
| | - Kathleen R. Ryan
- Department of Developmental Biology, Stanford
University School of Medicine, 300 Beckman Center, Stanford, CA 94305;
Department of Chemistry, Stanford University,
375 North-South Mall, MC 5080, Stanford, CA 94305; and
Department of Applied Physics, Stanford
University, Stanford, CA 94305
| | - W. E. Moerner
- Department of Developmental Biology, Stanford
University School of Medicine, 300 Beckman Center, Stanford, CA 94305;
Department of Chemistry, Stanford University,
375 North-South Mall, MC 5080, Stanford, CA 94305; and
Department of Applied Physics, Stanford
University, Stanford, CA 94305
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford
University School of Medicine, 300 Beckman Center, Stanford, CA 94305;
Department of Chemistry, Stanford University,
375 North-South Mall, MC 5080, Stanford, CA 94305; and
Department of Applied Physics, Stanford
University, Stanford, CA 94305
| | - Harley H. McAdams
- Department of Developmental Biology, Stanford
University School of Medicine, 300 Beckman Center, Stanford, CA 94305;
Department of Chemistry, Stanford University,
375 North-South Mall, MC 5080, Stanford, CA 94305; and
Department of Applied Physics, Stanford
University, Stanford, CA 94305
- To whom correspondence should be addressed. E-mail:
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12
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Cowan AE, Koppel DE, Setlow B, Setlow P. A soluble protein is immobile in dormant spores of Bacillus subtilis but is mobile in germinated spores: implications for spore dormancy. Proc Natl Acad Sci U S A 2003; 100:4209-14. [PMID: 12646705 PMCID: PMC404470 DOI: 10.1073/pnas.0636762100] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2002] [Indexed: 11/18/2022] Open
Abstract
Fluorescence redistribution after photobleaching has been used to show that a cytoplasmic GFP fusion is immobile in dormant spores of Bacillus subtilis but becomes freely mobile in germinated spores in which cytoplasmic water content has increased approximately 2-fold. The GFP immobility in dormant spores is not due to the high levels of dipicolinic acid in the spore cytoplasm, because GFP was also immobile in germinated cwlD spores that had excreted their dipicolinic acid but where cytoplasmic water content had only increased to a level similar to that in dormant spores of several other Bacillus species. The immobility of a normally mobile protein in dormant wild-type spores and germinated cwlD spores is consistent with the lack of metabolism and enzymatic activity in these spores and suggests that protein immobility, presumably due to low water content, is a major reason for the metabolic dormancy of spores of Bacillus species.
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Affiliation(s)
- Ann E Cowan
- Center for Biomedical Imaging Technology, University of Connecticut Health Center, Farmington, CT 06032, USA
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13
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de Pedro MA, Young KD, Höltje JV, Schwarz H. Branching of Escherichia coli cells arises from multiple sites of inert peptidoglycan. J Bacteriol 2003; 185:1147-52. [PMID: 12562782 PMCID: PMC142844 DOI: 10.1128/jb.185.4.1147-1152.2003] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some strains of Escherichia coli defective for dacA, the gene coding for penicillin-binding protein 5, exhibit a strong branching phenotype when cell division is blocked. Since such branch formation implies a differentiation of polar caps at ectopic locations in the cell envelope, we analyzed murein segregation and observed a strong correlation between areas of inert murein and these morphological anomalies. In particular, the tips of branches exhibited the same properties as those described for polar caps of wild-type cells, i.e., the synthesis and turnover of murein were inhibited. Also, the mobility of cell envelope proteins was apparently constrained in areas with morphological defects. Polar regions of branching cells and sacculi had aberrant morphologies with a very high frequency. Of special interest was that areas of inert murein at polar caps were often split by areas of active synthesis, a situation unlike that observed in wild-type cells. These observations suggest that in dacA mutants, branches and other morphological anomalies may arise from split polar caps or by de novo generation of new poles built around inert peptidoglycan patches in the side walls of the cell.
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Affiliation(s)
- Miguel A de Pedro
- Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain.
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14
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Carballido-López R, Errington J. The bacterial cytoskeleton: in vivo dynamics of the actin-like protein Mbl of Bacillus subtilis. Dev Cell 2003; 4:19-28. [PMID: 12530960 DOI: 10.1016/s1534-5807(02)00403-3] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mbl is a bacterial actin homolog that controls cell morphogenesis in Bacillus subtilis. A functional GFP-Mbl fusion protein was used to examine the behavior of the helical cables formed by Mbl protein in live B. subtilis cells. The cables undergo dynamic changes during cell cycle progression. They are stable but not rigid while elongating in parallel with cell growth, and they require septum formation to divide/cleave. Fluorescence recovery after photobleaching (FRAP) analysis showed that the cables are continuously remodeled during cell elongation. Turnover occurs along the length of the helical Mbl filaments, with no obvious polarity and a recovery half-time of about 8 min. These findings have important implications for the nature of bacterial cell wall architecture and synthesis.
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Affiliation(s)
- Rut Carballido-López
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE, Oxford, United Kingdom
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15
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Santini CL, Bernadac A, Zhang M, Chanal A, Ize B, Blanco C, Wu LF. Translocation of jellyfish green fluorescent protein via the Tat system of Escherichia coli and change of its periplasmic localization in response to osmotic up-shock. J Biol Chem 2001; 276:8159-64. [PMID: 11099493 DOI: 10.1074/jbc.c000833200] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial twin arginine translocation (Tat) pathway is capable of exporting cofactor-containing enzymes into the periplasm. To assess the capacity of the Tat pathway to export heterologous proteins and to gain information about the property of the periplasm, we fused the twin arginine signal peptide of the trimethylamine N-oxide reductase to the jellyfish green fluorescent protein (GFP). Unlike the Sec pathway, the Tat system successfully exported correctly folded GFP into the periplasm of Escherichia coli. Interestingly, GFP appeared as a halo in most cells and occasionally showed a polar localization in wild type strains. When subjected to a mild osmotic up-shock, GFP relocalized very quickly at the two poles of the cells. The conversion from the halo structure to a periplasmic gathering at particular locations was also observed with spherical cells of the DeltarodA-pbpA mutant or of the wild type strain treated with lysozyme. Therefore, the periplasm is not a uniform compartment and the polarization of GFP is unlikely to be caused by simple invagination of the cytoplasmic membrane at the poles. Moreover, the polar gathering of GFP is reversible; the reversion was accelerated by glucose and inhibited by azide and carbonyl cyanide m-chlorophenylhydrazone, indicating an active adaptation of the bacteria to the osmolarity in the medium. These results strongly suggest a relocalization of periplasmic substances in response to environmental changes. The polar area might be the preferential zone where bacteria sense the change in the environment.
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Affiliation(s)
- C L Santini
- Laboratoire de Chimie Bactérienne, UPR9043, Institut de Biologie Structurale et Microbiologie, CNRS, 31 chemin Joseph Aiguier, F-13402 Marseille cedex 20, France
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16
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Abstract
The mechanism responsible for creating the division site in the right place at the right time in bacteria is unknown. It has been attributed to the formation of proteolipid domains in the cytoplasmic membrane surrounding the nucleoids. We interpret the growing evidence for this hypothesis by invoking hyperstructures, which exist at a level of organization intermediate between macromolecules and genes. Non-equilibrium hyperstructures comprise the genes, mRNA proteins and lipids required for a particular function such as cell division, and assemble and disassemble according to the needs of the cell.
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Affiliation(s)
- V Norris
- Laboratoire des Processus Intégratifs Cellulaires, UPRESA CNRS 6037, IFR 'Systèmes Intégrés', Faculté des Sciences et Techniques, Université de Rouen, 76821 cedex, Mont-Saint-Aignan, France.
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17
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Abstract
Bacterial membrane and nucleoids were stained concurrently by the lipophilic styryl dye FM 4-64 [N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl) hexatrienyl)pyridinium dibromide] and 4',6-diamidino-2-phenylindole (DAPI), respectively, and studied using fluorescence microscopy imaging. Observation of plasmolysed cells indicated that FM 4-64 stained the inner membrane preferentially. In live Escherichia coli pbpB cells and filaments, prepared on wet agar slabs, an FM 4-64 staining pattern developed in the form of dark bands. In dividing cells, the bands occurred mainly at the constriction sites and, in filaments, between partitioning nucleoids. The FM 4-64 pattern of dark bands in filaments was abolished after inhibiting protein synthesis with chloramphenicol. It is proposed that the staining patterns reflect putative membrane domains formed by DNA-membrane interactions and have functional implications in cell division.
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Affiliation(s)
- I Fishov
- Department of Life Sciences, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 84105, Israel.
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18
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Abstract
Bacteria can survive dramatic osmotic shifts. Osmoregulatory responses mitigate the passive adjustments in cell structure and the growth inhibition that may ensue. The levels of certain cytoplasmic solutes rise and fall in response to increases and decreases, respectively, in extracellular osmolality. Certain organic compounds are favored over ions as osmoregulatory solutes, although K+ fluxes are intrinsic to the osmoregulatory response for at least some organisms. Osmosensors must undergo transitions between "off" and "on" conformations in response to changes in extracellular water activity (direct osmosensing) or resulting changes in cell structure (indirect osmosensing). Those located in the cytoplasmic membranes and nucleoids of bacteria are positioned for indirect osmosensing. Cytoplasmic membrane-based osmosensors may detect changes in the periplasmic and/or cytoplasmic solvent by experiencing changes in preferential interactions with particular solvent constituents, cosolvent-induced hydration changes, and/or macromolecular crowding. Alternatively, the membrane may act as an antenna and osmosensors may detect changes in membrane structure. Cosolvents may modulate intrinsic biomembrane strain and/or topologically closed membrane systems may experience changes in mechanical strain in response to imposed osmotic shifts. The osmosensory mechanisms controlling membrane-based K+ transporters, transcriptional regulators, osmoprotectant transporters, and mechanosensitive channels intrinsic to the cytoplasmic membrane of Escherichia coli are under intensive investigation. The osmoprotectant transporter ProP and channel MscL act as osmosensors after purification and reconstitution in proteoliposomes. Evidence that sensor kinase KdpD receives multiple sensory inputs is consistent with the effects of K+ fluxes on nucleoid structure, cellular energetics, cytoplasmic ionic strength, and ion composition as well as on cytoplasmic osmolality. Thus, osmoregulatory responses accommodate and exploit the effects of individual cosolvents on cell structure and function as well as the collective contribution of cosolvents to intracellular osmolality.
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Affiliation(s)
- J M Wood
- Department of Microbiology and Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Guelph, Ontario, Canada N1G
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20
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Affiliation(s)
- L I Rothfield
- Department of Microbiology, University of Connecticut Health Center, Farmington 06030, USA
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Lindsay MR, Webb RI, Fuerst JA. Pirellulosomes: a new type of membrane-bounded cell compartment in planctomycete bacteria of the genus Pirellula. Microbiology (Reading) 1997; 143:739-748. [DOI: 10.1099/00221287-143-3-739] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A distinct type of cellular organization was found in two species of the planctomycete genus Pirellula, Pirellula marina and Pirellula staleyi. Both species possess two distinct regions within the cell which are separated by a single membrane. The major region of the cell, the pirellulosome, contains the fibrillar condensed nucleoid. The other area, the polar cap region, forms a continuous layer surrounding the entire pirellulosome and displays a cap of asymmetrically distributed material at one cell pole. Immuno- and cytochemical-labelling of P. marina demonstrated that DNA is located exclusively within the pirellulosome; cell RNA is concentrated in the pirellulosome, with some RNA also located in the polar cap region.
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Affiliation(s)
- Margaret R. Lindsay
- Department of Microbiology, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Richard I. Webb
- Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland 4072, Australia
- Department of Microbiology, University of Queensland, Brisbane, Queensland 4072, Australia
| | - John A. Fuerst
- Department of Microbiology, University of Queensland, Brisbane, Queensland 4072, Australia
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22
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Norris V. Hypothesis: chromosome separation in Escherichia coli involves autocatalytic gene expression, transertion and membrane-domain formation. Mol Microbiol 1995; 16:1051-7. [PMID: 8577241 DOI: 10.1111/j.1365-2958.1995.tb02330.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To explain how daughter chromosomes are separated into discrete nucleoids and why chromosomes are partitioned with pole preferences, I propose that differential gene expression occurs during DNA replication in Escherichia coli. This differential gene expression means that the daughter chromosomes have different patterns of gene expression and that cell division is not a simple process of binary fission. Differential gene expression arises from autocatalytic gene expression and creates a separate proteolipid domain around each developing chromosome via the coupled transcription-translation-insertion of proteins into membranes (transertion). As these domains are immiscible, daughter chromosomes are simultaneously replicated and separated into discrete nucleoids. I also propose that the partitioning relationship between chromosome age and cell age arises because the poles of cells have a proteolipid composition that favours transertion from one nucleoid rather than from the other. This hypothesis forms part of an ensemble of related hypotheses which attempt to explain cell division, differentiation and wall growth in bacteria in terms of the physical properties and interactions of the principal constituents of cells.
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Affiliation(s)
- V Norris
- Department of Microbiology and Immunology, School of Medicine, University of Leicester, UK
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23
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Abstract
The harmonious growth and cell-to-cell uniformity of steady-state bacterial populations indicate the existence of a well-regulated cell cycle, responding to a set of internal signals. In Escherichia coli, the key events of this cycle are the initiation of DNA replication, nucleoid segregation and the initiation of cell division. The replication initiator is the DnaA protein. In nucleoid segregation, the MukB protein, required for proper partitioning, may be a member of the myosin-kinesin superfamily of mechanoenzymes. In cell division, the FtsZ protein has a tubulin motif, is a GTPase and polymerizes in a ring around midcell during septation; the FtsA protein has an actin-like structure. The nature of the internal signals triggering these events is not known but candidates include cell mass, the superhelical density of the chromosome and the concentration of two regulatory nucleotides, cyclic AMP and ppGpp. The involvement of cytoskeletal-like proteins in key cycle events encourages the notion of a fundamental biological unity in cell cycle regulation in all organisms.
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Affiliation(s)
- D Vinella
- Institut Jacques Monod, CNRS, Université Paris 7, France
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24
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Stephens C, Jenal U, Shapiro L. Expression of cell polarity during Caulobacter differentiation. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1044-5781(06)80080-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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25
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Affiliation(s)
- J W Payne
- School of Biological Sciences, University of Wales, UK
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26
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27
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Kocks C, Hellio R, Gounon P, Ohayon H, Cossart P. Polarized distribution of Listeria monocytogenes surface protein ActA at the site of directional actin assembly. J Cell Sci 1993; 105 ( Pt 3):699-710. [PMID: 8408297 DOI: 10.1242/jcs.105.3.699] [Citation(s) in RCA: 142] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The facultative intracellular pathogen Listeria monocytogenes can infect host tissues by using directional actin assembly to propel itself from one cell into another. The movement is generated by continuous actin assembly from one end of the bacterium into a tail, which is left behind in the cytoplasm. Bacterial actin assembly requires expression of the bacterial gene actA. We have used immunocytochemistry to show that the actA gene product, ActA, is distributed asymmetrically on the bacterial surface: it is not expressed at one pole and is increasingly concentrated towards the other. This polarized distribution of ActA was linked to bacterial division: ActA protein was not, or only faintly, expressed at the pole that had been formed during the previous division. On intracellular bacteria ActA was expressed at the site of actin assembly, suggesting that ActA may be involved in actin filament nucleation off the bacterial surface. We predict that the asymmetrical distribution of this protein is required for the ability of intracellular Listeria to move in the direction of the non-ActA expressing pole.
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Affiliation(s)
- C Kocks
- Laboratoire de Génétique Moléculaire des Listeria, Institut Pasteur, Paris, France
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28
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Warnes A, Brown MR, Fooks AR, Shuttleworth H, Dowsett AB, Melling J, Stephenson JR. The membrane binding C-terminus of protein A from Staphylococcus aureus affects its cellular localization and causes structural deformation when expressed in Escherichia coli. Curr Microbiol 1993; 26:337-44. [PMID: 7763641 DOI: 10.1007/bf01576266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Protein A from Staphylococcus aureus is a powerful diagnostic reagent and has several uses in human disease therapy. Expression in non-pathogenic Escherichia coli containing recombinant plasmids coding for this protein has increased its availability, but can reduce the stability of the plasmid-bearing host. By employing immune electron microscopy, we have determined that E. coli containing stable plasmids coding for a truncated version of protein A, without the membrane binding site, secrete this protein through the cytoplasmic membrane and into the periplasmic space, where it accumulates. E. coli containing unstable plasmids, however, which code for the complete protein including the membrane-binding site, target the protein into the cytoplasmic membrane. This accumulation of protein A in the E. coli cytoplasmic membrane inhibits the formation of septa between dividing cells and results in aberrant elongated, multi-chromosomal forms.
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Affiliation(s)
- A Warnes
- PHLS Centre for Applied Microbiology and Research, Salisbury, UK
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29
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Greenberg ML, Axelrod D. Anomalously slow mobility of fluorescent lipid probes in the plasma membrane of the yeast Saccharomyces cerevisiae. J Membr Biol 1993; 131:115-27. [PMID: 8441175 DOI: 10.1007/bf02791320] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We measured the lateral mobility of two fluorescent lipid probes dioctadecylindocarbocyanine (diI) and tetramethyl rhodamine phosphatidylethanolamine (R-PE) in the plasma membranes of Saccharomyces cerevisiae ino1 and opi3 spheroplasts. These are well-characterized strains with mutations in the inositol and phosphatidylcholine biosynthetic pathways. Membrane phospholipid composition was altered by growing these mutants in the presence or absence of inositol and choline. Lateral mobility was measured by fluorescence recovery after photobleaching (FRAP). Microscopic fluorescence polarization employing CCD digital imaging produced an ordered orientation distribution of the lipid probe diI, confirming that at least one of the probes was largely incorporated into the bilayer membrane. Our results demonstrated anomalously slow mobility of both lipid probes for both mutants, regardless of whether the lipid composition was near normal or dramatically altered in relative composition of phosphatidylinositol and phosphatidylcholine. Trypsinization of the spheroplasts to remove surface proteins resulted in markedly increased lateral mobility. However, even in trypsinized spheroplasts, mobility was still somewhat lower than the mobility observed in the membrane of mammalian cells, such as rat smooth muscle culture cells tested here for comparison.
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Affiliation(s)
- M L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, Michigan
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30
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Affiliation(s)
- D Vinella
- Institut Jacques Monod, C.N.R.S., Université Paris 7, 2 place Jussieu, 75251 Paris Cedex 05, France
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31
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Norris V. Phospholipid domains determine the spatial organization of the Escherichia coli cell cycle: the membrane tectonics model. J Theor Biol 1992; 154:91-107. [PMID: 1573903 DOI: 10.1016/s0022-5193(05)80190-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Escherichia coli normally divides at its equator between segregated nucleoids. Such division is inhibited during perturbations of chromosome replication (even in the absence of inducible division inhibitors); eventually, division resumes at sites which are not at this equator. Escherichia coli will also divide at its poles to generate minicells following overproduction of the FtsZ or MinE proteins. The mechanisms underlying the division inhibition and the positioning of the division sites are unknown. In the membrane tectonics model, I propose that the formation of phospholipid domains within the cytoplasmic membrane positions division sites. The particular phospholipid composition of a domain attracts particular proteins and determines their activity; conversely, particular proteins change the composition of domains. Principally via such proteins, the interaction of the chromosome with the membrane creates a chromosomal domain. The development of chromosomal domains during replication and nucleoid formation contributes to the formation and positioning of a septal domain between them. During septation (cell division), this septal domain matures into a polar domain. Each domain attracts and activates different enzymes. The septal domain attracts and activates enzymes necessary for septation. Preventing the formation of the septal domain by preventing chromosome replication prevents normal division. Altering the composition of the polar domain may allow septation enzymes to function there and generate minicells. A corollary of the model explains how the formation of an origin domain by the attachment of hemi-methylated origin DNA to the membrane may underlie the creation and migration of structures within the envelope, the periseptal annuli.
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Affiliation(s)
- V Norris
- Department of Genetics, University of Leicester, U.K
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32
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Nesmeyanova MA, Tsfasman IM, Karamyshev AL, Suzina NE. Secretion of the overproduced periplasmic PhoA protein into the medium and accumulation of its precursor in phoA-transformed Escherichia coli strains: involvement of outer membrane vesicles. World J Microbiol Biotechnol 1991; 7:394-406. [DOI: 10.1007/bf00329408] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/1990] [Revised: 12/10/1990] [Indexed: 10/26/2022]
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33
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Higgins CF, Hyde SC, Mimmack MM, Gileadi U, Gill DR, Gallagher MP. Binding protein-dependent transport systems. J Bioenerg Biomembr 1990; 22:571-92. [PMID: 2229036 DOI: 10.1007/bf00762962] [Citation(s) in RCA: 215] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Bacterial binding protein-dependent transport systems are the best characterized members of a superfamily of transporters which are structurally, functionally, and evolutionary related to each other. These transporters are not only found in bacteria but also in yeasts, plants, and animals including man, and include both import and export systems. Although any single system is relatively specific, different systems handle very different substrates which can be inorganic ions, amino acids, sugars, large polysaccharides, or even proteins. Some are of considerable medical importance, including Mdr, the protein responsible for multidrug resistance in human tumors, and the product of the cystic fibrosis locus. In this article we review the current state of knowledge on the structure and function of the protein components of these transporters, the mechanism by which transport is mediated, and the role of ATP in the transport process.
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Affiliation(s)
- C F Higgins
- ICRF Laboratories, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, England
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34
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Abstract
In prokaryotic and eukaryotic organisms, proteins are efficiently sorted to reach their final destinations in a whole range of subcellular compartments. Targeting is mediated by hydrophobic signal sequences or hydrophilic targeting sequences depending upon the compartment, these sequences being often processed. Proteins cannot be translocated through a membrane in a tightly folded stage, they must have a loose conformation, the so-called 'translocation competent state', which is usually kept through interactions with chaperones. In addition to these cytosolic receptor-like components, receptors are also present on the target membranes. Depending upon the organelles and organisms, two different energy sources have been identified, energy rich phosphate bonds (ATP and GTP) and a potential across the target membrane. Besides the signal peptides, various classes of signals have been identified to account for topologies of membrane proteins. Protein secretion in bacterial organisms has been extensively studied. Various classes of proteins use different strategies, some of these may also be used in eukaryotic cells.
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Affiliation(s)
- C J Lazdunski
- Centre de Biochemie et de Biologie Moléculaire du CNRS, Marseille, France
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35
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Affiliation(s)
- L I Rothfield
- Department of Microbiology, University of Connecticut Health Center, Farmington 06032
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