1
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Roterman I, Stapor K, Konieczny L. Transmembrane proteins-Different anchoring systems. Proteins 2024; 92:593-609. [PMID: 38062872 DOI: 10.1002/prot.26646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/03/2023] [Accepted: 11/17/2023] [Indexed: 04/13/2024]
Abstract
Transmembrane proteins are active in amphipathic environments. To stabilize the protein in such surrounding the exposure of hydrophobic residues on the protein surface is required. Transmembrane proteins are responsible for the transport of various molecules. Therefore, they often represent structures in the form of channels. This analysis focused on the stability and local flexibility of transmembrane proteins, particularly those related to their biological activity. Different forms of anchorage were identified using the fuzzy oil-drop model (FOD) and its modified form, FOD-M. The mainly helical as well as β-barrel structural forms are compared with respect to the mechanism of stabilization in the cell membrane. The different anchoring system was found to stabilize protein molecules with possible local fluctuation.
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Affiliation(s)
- Irena Roterman
- Department of Bioinformatics and Telemedicine, Jagiellonian University-Medical College, Krakow, Poland
| | - Katarzyna Stapor
- Faculty of Automatic, Electronics and Computer Science, Department of Applied Informatics, Silesian University of Technology, Gliwice, Poland
| | - Leszek Konieczny
- Chair of Medical Biochemistry, Jagiellonian University-Medical College, Krakow, Poland
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2
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Schaich M, Sobota D, Sleath H, Cama J, Keyser UF. Characterization of lipid composition and diffusivity in OLA generated vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183359. [PMID: 32416194 PMCID: PMC7322398 DOI: 10.1016/j.bbamem.2020.183359] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 04/15/2020] [Accepted: 05/11/2020] [Indexed: 11/19/2022]
Abstract
Giant Unilamellar Vesicles (GUVs) are a versatile tool in many branches of science, including biophysics and synthetic biology. Octanol-Assisted Liposome Assembly (OLA), a recently developed microfluidic technique enables the production and testing of GUVs within a single device under highly controlled experimental conditions. It is therefore gaining significant interest as a platform for use in drug discovery, the production of artificial cells and more generally for controlled studies of the properties of lipid membranes. In this work, we expand the capabilities of the OLA technique by forming GUVs of tunable binary lipid mixtures of DOPC, DOPG and DOPE. Using fluorescence recovery after photobleaching we investigated the lateral diffusion coefficients of lipids in OLA liposomes and found the expected values in the range of 1 μm2/s for the lipid systems tested. We studied the OLA derived GUVs under a range of conditions and compared the results with electroformed vesicles. Overall, we found the lateral diffusion coefficients of lipids in vesicles obtained with OLA to be quantitatively similar to those in vesicles obtained via traditional electroformation. Our results provide a quantitative biophysical validation of the quality of OLA derived GUVs, which will facilitate the wider use of this versatile platform.
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Affiliation(s)
- Michael Schaich
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Diana Sobota
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Hannah Sleath
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Jehangir Cama
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom; Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, United Kingdom; College of Engineering, Mathematics and Physical Sciences, University of Exeter, Harrison Building, Streatham Campus, North Park Road, Exeter EX4 4QF, United Kingdom.
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
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3
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Jacobson K, Liu P, Lagerholm BC. The Lateral Organization and Mobility of Plasma Membrane Components. Cell 2020; 177:806-819. [PMID: 31051105 DOI: 10.1016/j.cell.2019.04.018] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 02/01/2019] [Accepted: 04/09/2019] [Indexed: 01/22/2023]
Abstract
Over the last several decades, an impressive array of advanced microscopic and analytical tools, such as single-particle tracking and nanoscopic fluorescence correlation spectroscopy, has been applied to characterize the lateral organization and mobility of components in the plasma membrane. Such analysis can tell researchers about the local dynamic composition and structure of membranes and is important for predicting the outcome of membrane-based reactions. However, owing to the unresolved complexity of the membrane and the structures peripheral to it, identification of the detailed molecular origin of the interactions that regulate the organization and mobility of the membrane has not proceeded quickly. This Perspective presents an overview of how cell-surface structure may give rise to the types of lateral mobility that are observed and some potentially fruitful future directions to elucidate the architecture of these structures in more molecular detail.
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Affiliation(s)
- Ken Jacobson
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Ping Liu
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, 430074 Hubei, China
| | - B Christoffer Lagerholm
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK
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4
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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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5
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Nanoscale analysis reveals no domain formation of glycosylphosphatidylinositol-anchored protein SAG1 in the plasma membrane of living Toxoplasma gondii. Histochem Cell Biol 2019; 152:365-375. [PMID: 31542792 DOI: 10.1007/s00418-019-01814-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2019] [Indexed: 10/25/2022]
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins typically localise to lipid rafts. GPI-anchored protein microdomains may be present in the plasma membrane; however, they have been studied using heterogeneously expressed GPI-anchored proteins, and the two-dimensional distributions of endogenous molecules in the plasma membrane are difficult to determine at the nanometre scale. Here, we used immunoelectron microscopy using a quick-freezing and freeze-fracture labelling (QF-FRL) method to examine the distribution of the endogenous GPI-anchored protein SAG1 in Toxoplasma gondii at the nanoscale. QF-FRL physically immobilised molecules in situ, minimising the possibility of artefactual perturbation. SAG1 labelling was observed in the exoplasmic, but not cytoplasmic, leaflets of T. gondii plasma membrane, whereas none was detected in any leaflet of the inner membrane complex. Point pattern analysis of SAG1 immunogold labelling revealed mostly random distribution in T. gondii plasma membrane. The present method obtains information on the molecular distribution of natively expressed GPI-anchored proteins and demonstrates that SAG1 in T. gondii does not form significant microdomains in the plasma membrane.
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6
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Benhamou M, Kaidi H, Hachem EK. Determination and classification of the effective potentials between nanoparticles and nanopores within bilayer-membranes versus their geometry and density. Experimental inspiration. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.08.073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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7
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Su Y, Lai PY, Ackerson BJ, Cao X, Han Y, Tong P. Colloidal diffusion over a quasicrystalline-patterned surface. J Chem Phys 2017; 146:214903. [DOI: 10.1063/1.4984938] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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8
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Bernstein J, Fricks J. Analysis of single particle diffusion with transient binding using particle filtering. J Theor Biol 2016; 401:109-21. [PMID: 27107737 DOI: 10.1016/j.jtbi.2016.04.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 10/27/2015] [Accepted: 04/11/2016] [Indexed: 12/27/2022]
Abstract
Diffusion with transient binding occurs in a variety of biophysical processes, including movement of transmembrane proteins, T cell adhesion, and caging in colloidal fluids. We model diffusion with transient binding as a Brownian particle undergoing Markovian switching between free diffusion when unbound and diffusion in a quadratic potential centered around a binding site when bound. Assuming the binding site is the last position of the particle in the unbound state and Gaussian observational error obscures the true position of the particle, we use particle filtering to predict when the particle is bound and to locate the binding sites. Maximum likelihood estimators of diffusion coefficients, state transition probabilities, and the spring constant in the bound state are computed with a stochastic Expectation-Maximization (EM) algorithm.
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Affiliation(s)
- Jason Bernstein
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States
| | - John Fricks
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States.
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9
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Saha S, Anilkumar AA, Mayor S. GPI-anchored protein organization and dynamics at the cell surface. J Lipid Res 2015; 57:159-75. [PMID: 26394904 DOI: 10.1194/jlr.r062885] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Indexed: 01/05/2023] Open
Abstract
The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or Förster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite.
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Affiliation(s)
- Suvrajit Saha
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India
| | - Anupama Ambika Anilkumar
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India Shanmugha Arts, Science, Technology and Research Academy, Thanjavur 613401, India
| | - Satyajit Mayor
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore 560065, India
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10
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Ma XG, Lai PY, Ackerson BJ, Tong P. Colloidal transport and diffusion over a tilted periodic potential: dynamics of individual particles. SOFT MATTER 2015; 11:1182-1196. [PMID: 25562695 DOI: 10.1039/c4sm02387k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A tilted two-layer colloidal system is constructed for the study of force-assisted barrier-crossing dynamics over a periodic potential. The periodic potential is provided by the bottom layer colloidal spheres forming a fixed crystalline pattern on a glass substrate. The corrugated surface of the bottom colloidal crystal provides a gravitational potential field for the top layer diffusing particles. By tilting the sample at an angle θ with respect to the vertical (gravity) direction, a tangential component of the gravitational force F is applied to the diffusing particles. The measured mean drift velocity v(F, Eb) and diffusion coefficient D(F, Eb) of the particles as a function of F and energy barrier height Eb agree well with the exact results of the one-dimensional drift velocity (R. L. Stratonovich, Radiotekh. Elektron, 1958, 3, 497) and diffusion coefficient (P. Reimann, et al., Phys. Rev. Lett., 2001, 87, 010602 and P. Reimann, et al., Phys. Rev. E, 2002, 65, 031104). Based on these exact results, we show analytically and verify experimentally that there exists a scaling region, in which v(F, Eb) and D(F, Eb) both scale as ν'(F)exp[-E(F)/kBT], where the Arrhenius pre-factor ν'(F) and effective barrier height E(F) are both modified by F. The experiment demonstrates the applications of this model system in evaluating different scaling forms of ν'(F) and E(F) and their accuracy, in order to extract useful information about the external potential, such as the intrinsic barrier height Eb.
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Affiliation(s)
- Xiao-guang Ma
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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11
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Nicolson GL. The Fluid—Mosaic Model of Membrane Structure: Still relevant to understanding the structure, function and dynamics of biological membranes after more than 40years. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1451-66. [DOI: 10.1016/j.bbamem.2013.10.019] [Citation(s) in RCA: 442] [Impact Index Per Article: 44.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 10/08/2013] [Accepted: 10/18/2013] [Indexed: 12/21/2022]
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12
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Hsieh CL, Spindler S, Ehrig J, Sandoghdar V. Tracking Single Particles on Supported Lipid Membranes: Multimobility Diffusion and Nanoscopic Confinement. J Phys Chem B 2014; 118:1545-54. [DOI: 10.1021/jp412203t] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Chia-Lung Hsieh
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - Susann Spindler
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
| | - Jens Ehrig
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
| | - Vahid Sandoghdar
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
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13
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Abstract
The Fluid-Mosaic Membrane Model of cell membrane structure was based on thermodynamic principals and the available data on component lateral mobility within the membrane plane [Singer SJ, Nicolson GL. The Fluid Mosaic Model of the structure of cell membranes. Science 1972; 175: 720-731]. After more than forty years the model remains relevant for describing the basic nano-scale structures of a variety of biological membranes. More recent information, however, has shown the importance of specialized membrane domains, such as lipid rafts and protein complexes, in describing the macrostructure and dynamics of biological membranes. In addition, membrane-associated cytoskeletal structures and extracellular matrix also play roles in limiting the mobility and range of motion of membrane components and add new layers of complexity and hierarchy to the original model. An updated Fluid-Mosaic Membrane Model is described, where more emphasis has been placed on the mosaic nature of cellular membranes where protein and lipid components are more crowded and limited in their movements in the membrane plane by lipid-lipid, protein-protein and lipid-protein interactions as well as cell-matrix, cell-cell and cytoskeletal interactions. These interactions are important in restraining membrane components and maintaining the unique mosaic organization of cell membranes into functional, dynamic domains.
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Affiliation(s)
- Garth L Nicolson
- The Institute for Molecular Medicine, Department of Molecular Pathology, Huntington Beach, CA, USA
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14
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Weigel AV, Ragi S, Reid ML, Chong EKP, Tamkun MM, Krapf D. Obstructed diffusion propagator analysis for single-particle tracking. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:041924. [PMID: 22680515 DOI: 10.1103/physreve.85.041924] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Indexed: 06/01/2023]
Abstract
We describe a method for the analysis of the distribution of displacements, i.e., the propagators, of single-particle tracking measurements for the case of obstructed subdiffusion in two-dimensional membranes. The propagator for the percolation cluster is compared with a two-component mobility model against Monte Carlo simulations. To account for diffusion in the presence of obstacle concentrations below the percolation threshold, a propagator that includes the transient motion in finite percolation clusters and hopping between obstacle-induced compartments is derived. Finally, these models are shown to be effective in the analysis of Kv2.1 channel diffusive measurements in the membrane of living mammalian cells.
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Affiliation(s)
- Aubrey V Weigel
- School of Biomedical Engineering, Colorado State University, Fort Collins, Colorado 80523, USA
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15
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Affiliation(s)
- A J Freemont
- Department of Pathological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
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16
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Vladimirou E, Li M, Aldridge CP, Frigerio L, Kirkilionis M, Robinson C. Diffusion of a membrane protein, Tat subunit Hcf106, is highly restricted within the chloroplast thylakoid network. FEBS Lett 2009; 583:3690-6. [PMID: 19854178 DOI: 10.1016/j.febslet.2009.10.057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Revised: 10/16/2009] [Accepted: 10/19/2009] [Indexed: 11/17/2022]
Abstract
The thylakoid membrane forms stacked thylakoids interconnected by 'stromal' lamellae. Little is known about the mobility of proteins within this system. We studied a stromal lamellae protein, Hcf106, by targeting an Hcf106-GFP fusion protein to the thylakoids and photobleaching. We find that even small regions fail to recover Hcf106-GFP fluorescence over periods of up to 3 min after photobleaching. The protein is thus either immobile within the thylakoid membrane, or its diffusion is tightly restricted within distinct regions. Autofluorescence from the photosystem II light-harvesting complex in the granal stacks likewise fails to recover. Integral membrane proteins within both the stromal and granal membranes are therefore highly constrained, possibly forming 'microdomains' that are sharply separated.
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Affiliation(s)
- Elina Vladimirou
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
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17
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Liu LN, Aartsma TJ, Thomas JC, Zhou BC, Zhang YZ. FRAP analysis on red alga reveals the fluorescence recovery is ascribed to intrinsic photoprocesses of phycobilisomes than large-scale diffusion. PLoS One 2009; 4:e5295. [PMID: 19381335 PMCID: PMC2667670 DOI: 10.1371/journal.pone.0005295] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Accepted: 03/26/2009] [Indexed: 11/28/2022] Open
Abstract
Background Phycobilisomes (PBsomes) are the extrinsic antenna complexes upon the photosynthetic membranes in red algae and most cyanobacteria. The PBsomes in the cyanobacteria has been proposed to present high lateral mobility on the thylakoid membrane surface. In contrast, direct measurement of PBsome motility in red algae has been lacking so far. Methodology/Principal Findings In this work, we investigated the dynamics of PBsomes in the unicellular red alga Porphyridium cruentum in vivo and in vitro, using fluorescence recovery after photobleaching (FRAP). We found that part of the fluorescence recovery could be detected in both partially- and wholly-bleached wild-type and mutant F11 (UTEX 637) cells. Such partial fluorescence recovery was also observed in glutaraldehyde-treated and betaine-treated cells in which PBsome diffusion should be restricted by cross-linking effect, as well as in isolated PBsomes immobilized on the glass slide. Conclusions/Significance On the basis of our previous structural results showing the PBsome crowding on the native photosynthetic membrane as well as the present FRAP data, we concluded that the fluorescence recovery observed during FRAP experiment in red algae is mainly ascribed to the intrinsic photoprocesses of the bleached PBsomes in situ, rather than the rapid diffusion of PBsomes on thylakoid membranes in vivo. Furthermore, direct observations of the fluorescence dynamics of phycoerythrins using FRAP demonstrated the energetic decoupling of phycoerythrins in PBsomes against strong excitation light in vivo, which is proposed as a photoprotective mechanism in red algae attributed by the PBsomes in response to excess light energy.
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Affiliation(s)
- Lu-Ning Liu
- State Key Lab of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan, People's Republic of China
- Department of Biophysics, Huygens Laboratory, Leiden University, Leiden, The Netherlands
| | - Thijs J. Aartsma
- Department of Biophysics, Huygens Laboratory, Leiden University, Leiden, The Netherlands
| | - Jean-Claude Thomas
- UMR 8186 CNRS & Ecole Normale Supérieure, Biologie Moléculaire des Organismes Photosynthétiques, Paris, France
| | - Bai-Cheng Zhou
- State Key Lab of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan, People's Republic of China
| | - Yu-Zhong Zhang
- State Key Lab of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan, People's Republic of China
- * E-mail:
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18
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Mirkovic T, Wilk KE, Curmi PMG, Scholes GD. Phycobiliprotein diffusion in chloroplasts of cryptophyte Rhodomonas CS24. PHOTOSYNTHESIS RESEARCH 2009; 100:7-17. [PMID: 19224391 DOI: 10.1007/s11120-009-9412-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 02/04/2009] [Indexed: 05/27/2023]
Abstract
Unicellular cryptophyte algae employ antenna proteins with phycobilin chromophores in their photosynthetic machinery. The mechanism of light harvesting in these organisms is significantly different than the energy funneling processes in phycobilisomes utilized by cyanobacteria and red algae. One of the most striking features of cryptophytes is the location of the water-soluble phycobiliproteins, which are contained within the intrathylakoid spaces and are not on the stromal side of the lamellae as in the red algae and cyanobacteria. Studies of mobility of phycobiliproteins at the lumenal side of the thylakoid membranes and how their diffusional behavior may influence the energy funneling steps in light harvesting are reported. Confocal microscopy and fluorescence recovery after photobleaching (FRAP) are used to measure the diffusion coefficient of phycoerythrin 545 (PE545), the primary light harvesting protein of Rhodomonas CS24, in vivo. It is concluded that the diffusion of PE545 in the lumen is inhibited, suggesting possible membrane association or aggregation as a potential source of mobility hindrance.
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Affiliation(s)
- Tihana Mirkovic
- Department of Chemistry, Institute for Optical Sciences, Centre for Quantum Information and Quantum Control, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada
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Lubelski A, Klafter J. Fluorescence correlation spectroscopy: the case of subdiffusion. Biophys J 2009; 96:2055-63. [PMID: 19289033 PMCID: PMC2717304 DOI: 10.1016/j.bpj.2008.10.069] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 10/09/2008] [Indexed: 11/21/2022] Open
Abstract
The theory of fluorescence correlation spectroscopy is revisited here for the case of subdiffusing molecules. Subdiffusion is assumed to stem from a continuous-time random walk process with a fat-tailed distribution of waiting times and can therefore be formulated in terms of a fractional diffusion equation (FDE). The FDE plays the central role in developing the fluorescence correlation spectroscopy expressions, analogous to the role played by the simple diffusion equation for regular systems. Due to the nonstationary nature of the continuous-time random walk/FDE, some interesting properties emerge that are amenable to experimental verification and may help in discriminating among subdiffusion mechanisms. In particular, the current approach predicts 1), a strong dependence of correlation functions on the initial time (aging); 2), sensitivity of correlation functions to the averaging procedure, ensemble versus time averaging (ergodicity breaking); and 3), that the basic mean-squared displacement observable depends on how the mean is taken.
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Affiliation(s)
- Ariel Lubelski
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel.
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20
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Abstract
Protein diffusion in and around the photosynthetic membrane must play a crucial role in photosynthetic functions including electron transport, regulation of light-harvesting, and biogenesis, turnover and repair of membrane components. Protein mobility is controlled by a complex web of specific interactions, plus the viscosity of the environment and the extent of macromolecular crowding. I discuss the techniques that can be used to measure protein mobility in photosynthetic membranes. I then summarize what we know about the constraints on protein mobility imposed by macromolecular aggregation and crowding in and around the thylakoid membranes of green plants and cyanobacteria, with particular reference to the fluidity of the thylakoid membrane and the aqueous phases on either side of the membrane (the stroma/cytoplasm and the thylakoid lumen). Current indications are that the stroma/cytoplasm is a relatively fluid environment, whereas protein mobility in the lumen may be extremely restricted. The thylakoid membrane itself has an intermediate fluidity: some protein complexes are virtually immobile, probably due to their incorporation into large, stable macromolecular aggregates. However, there is sufficient free space to allow the long-range diffusion of some complexes. Finally, I discuss some future directions for research in this area.
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Affiliation(s)
- Conrad W Mullineaux
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, UK.
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21
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Lubelski A, Klafter J. Fluorescence recovery after photobleaching: the case of anomalous diffusion. Biophys J 2008; 94:4646-53. [PMID: 18326658 PMCID: PMC2397333 DOI: 10.1529/biophysj.107.119081] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2007] [Accepted: 02/08/2008] [Indexed: 01/30/2023] Open
Abstract
The method of FRAP (fluorescence recovery after photobleaching), which has been broadly used to measure lateral mobility of fluorescent-labeled molecules in cell membranes, is formulated here in terms of continuous time random walks (CTRWs), which offer both analytical expressions and a scheme for numerical simulations. We propose an approach based on the CTRW and the corresponding fractional diffusion equation (FDE) to analyze FRAP results in the presence of anomalous subdiffusion. The FDE generalizes the simple diffusive picture, which has been applied to FRAP when assuming regular diffusion, to account for subdiffusion. We use a subordination relationship between the solutions of the fractional and normal diffusion equations to fit FRAP recovery curves obtained from CTRW simulations, and compare the fits to the commonly used approach based on the simple diffusion equation with a time dependent diffusion coefficient (TDDC). The CTRW and TDDC describe two different dynamical schemes, and although the CTRW formalism appears to be more complicated, it provides a physical description that underlies anomalous lateral diffusion.
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Affiliation(s)
- Ariel Lubelski
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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22
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Coscoy S, Huguet E, Amblard F. Statistical analysis of sets of random walks: how to resolve their generating mechanism. Bull Math Biol 2007; 69:2467-92. [PMID: 17896161 DOI: 10.1007/s11538-007-9227-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Accepted: 03/29/2007] [Indexed: 01/27/2023]
Abstract
The analysis of experimental random walks aims at identifying the process(es) that generate(s) them. It is in general a difficult task, because statistical dispersion within an experimental set of random walks is a complex combination of the stochastic nature of the generating process, and the possibility to have more than one simple process. In this paper, we study by numerical simulations how the statistical distribution of various geometric descriptors such as the second, third and fourth order moments of two-dimensional random walks depends on the stochastic process that generates that set. From these observations, we derive a method to classify complex sets of random walks, and resolve the generating process(es) by the systematic comparison of experimental moment distributions with those numerically obtained for candidate processes. In particular, various processes such as Brownian diffusion combined with convection, noise, confinement, anisotropy, or intermittency, can be resolved by using high order moment distributions. In addition, finite-size effects are observed that are useful for treating short random walks. As an illustration, we describe how the present method can be used to study the motile behavior of epithelial microvilli. The present work should be of interest in biology for all possible types of single particle tracking experiments.
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Affiliation(s)
- Sylvie Coscoy
- Physico-Chimie Curie (UMR 168) CNRS/Institut Curie, 26, Rue d'Ulm, 75248, Paris Cedex 05, France.
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23
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Abstract
We present a position Langevin equation for overdamped particle motion on rough two-dimensional surfaces. A Brownian dynamics algorithm is suggested to evolve this equation numerically, allowing for the prediction of effective (projected) diffusion coefficients over corrugated surfaces. In the case of static surface roughness, we find that a simple area-scaling prediction for the projected diffusion coefficient leads to seemingly quantitative agreement with numerical results. To study the effect of dynamic surface evolution on the diffusive process, we consider particle diffusion over a thermally fluctuating elastic membrane. Surface fluctuation has the effect of increasing the effective diffusivity toward a limiting annealed-surface value discussed previously. We argue that protein motion over cell surfaces spans a variety of physical regimes, making it impossible to identify a single approximation scheme appropriate to all measurements of interest.
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Affiliation(s)
- Ali Naji
- Department of Physics, University of California, Santa Barbara, California 93106-9530, USA
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24
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Abstract
Phage lambda lyses the host Escherichia coli at a precisely scheduled time after induction. Lysis timing is determined by the action of phage holins, which are small proteins that induce hole formation in the bacterium's cytoplasmic membrane. We present a two-stage nucleation model of lysis timing, with the nucleation of condensed holin rafts on the inner membrane followed by the nucleation of a hole within those rafts. The nucleation of holin rafts accounts for most of the delay of lysis after induction. Our simulations of this model recover the accurate lysis timing seen experimentally and show that the timing accuracy is optimal. An enhanced holin-holin interaction is needed in our model to recover experimental lysis delays after the application of membrane poison, and such early triggering of lysis is possible only after the inner membrane is supersaturated with holin. Antiholin reduces the delay between membrane depolarization and lysis and leads to an earlier time after which triggered lysis is possible.
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Affiliation(s)
- Gillian L Ryan
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
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25
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Soong R, Macdonald PM. PEG molecular weight and lateral diffusion of PEG-ylated lipids in magnetically aligned bicelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1805-14. [PMID: 17524353 DOI: 10.1016/j.bbamem.2007.03.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 03/07/2007] [Accepted: 03/27/2007] [Indexed: 11/30/2022]
Abstract
Lateral diffusion coefficients of PEG-ylated lipids with three different molecular weight PEG groups (1000, 2000 and 5000) were measured in magnetically-aligned bicelles using the stimulated echo (STE) pulsed field gradient (PEG) (1)H nuclear magnetic resonance (NMR) method. At concentrations below the PEG "mushroom-to-brush" transition, all three PEG-ylated lipids exhibited unrestricted lateral diffusion, with lateral diffusion coefficients comparable to those of corresponding non-PEG-ylated lipids and independent of PEG molecular weight. At concentrations above this transition, lateral diffusion slowed progressively with increasing concentration of PEG-ylated lipid as a result of surface crowding. As well, the lateral diffusion coefficients exhibited a pronounced decrease with increasing PEG group molecular weight and a diffusion-time dependence indicative of obstructed diffusion. We conclude that, while lateral diffusion of PEG-ylated lipids within lipid bilayers is determined primarily by the hydrophobic anchoring group, when crowding at the lipid bilayer surface becomes significant, the size of the extra-membranous domain, in this case the PEG group, can influence lateral diffusion, leading to decreased diffusivity with increasing size and producing obstructed diffusion at high crowding. These findings imply that similar considerations will pertain to lateral diffusion of membrane proteins with large extra-membranous domains.
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Affiliation(s)
- Ronald Soong
- Department of Chemistry, University of Toronto, 3359 Mississauga Road North, Mississauga, ON, Canada L5L 1C6
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26
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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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27
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Ohba T, Schirmer EC, Nishimoto T, Gerace L. Energy- and temperature-dependent transport of integral proteins to the inner nuclear membrane via the nuclear pore. ACTA ACUST UNITED AC 2005; 167:1051-62. [PMID: 15611332 PMCID: PMC2172626 DOI: 10.1083/jcb.200409149] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Resident integral proteins of the inner nuclear membrane (INM) are synthesized as membrane-integrated proteins on the peripheral endoplasmic reticulum (ER) and are transported to the INM throughout interphase using an unknown trafficking mechanism. To study this transport, we developed a live cell assay that measures the movement of transmembrane reporters from the ER to the INM by rapamycin-mediated trapping at the nuclear lamina. Reporter constructs with small (<30 kD) cytosolic and lumenal domains rapidly accumulated at the INM. However, increasing the size of either domain by 47 kD strongly inhibited movement. Reduced temperature and ATP depletion also inhibited movement, which is characteristic of membrane fusion mechanisms, but pharmacological inhibition of vesicular trafficking had no effect. Because reporter accumulation at the INM was inhibited by antibodies to the nuclear pore membrane protein gp210, our results support a model wherein transport of integral proteins to the INM involves lateral diffusion in the lipid bilayer around the nuclear pore membrane, coupled with active restructuring of the nuclear pore complex.
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Affiliation(s)
- Tomoyuki Ohba
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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28
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Joshua S, Mullineaux CW. Phycobilisome diffusion is required for light-state transitions in cyanobacteria. PLANT PHYSIOLOGY 2004; 135:2112-9. [PMID: 15286286 PMCID: PMC520783 DOI: 10.1104/pp.104.046110] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2004] [Revised: 05/28/2004] [Accepted: 05/28/2004] [Indexed: 05/18/2023]
Abstract
Phycobilisomes are the major accessory light-harvesting complexes of cyanobacteria and red algae. Studies using fluorescence recovery after photobleaching on cyanobacteria in vivo have shown that the phycobilisomes are mobile complexes that rapidly diffuse on the thylakoid membrane surface. By contrast, the PSII core complexes are completely immobile. This indicates that the association of phycobilisomes with reaction centers must be transient and unstable. Here, we show that when cells of the cyanobacterium Synechococcus sp. PCC7942 are immersed in buffers of high osmotic strength, the diffusion coefficient for the phycobilisomes is greatly decreased. This suggests that the interaction between phycobilisomes and reaction centers becomes much less transient under these conditions. We discuss the possible reasons for this. State transitions are a rapid physiological adaptation mechanism that regulates the way in which absorbed light energy is distributed between PSI and PSII. Immersing cells in high osmotic strength buffers inhibits state transitions by locking cells into whichever state they were in prior to addition of the buffer. The effect on state transitions is induced at the same buffer concentrations as the effect on phycobilisome diffusion. This implies that phycobilisome diffusion is required for state transitions. The main physiological role for phycobilisome mobility may be to allow such flexibility in light harvesting.
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Affiliation(s)
- Sarah Joshua
- Department of Biology, University College London, London WC1E 6BT, United Kingdom
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29
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Sarcina M, Mullineaux CW. Mobility of the IsiA Chlorophyll-binding Protein in Cyanobacterial Thylakoid Membranes. J Biol Chem 2004; 279:36514-8. [PMID: 15218021 DOI: 10.1074/jbc.m405881200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We are using fluorescence recovery after photobleaching (FRAP) to probe the dynamics of thylakoid membranes in vivo in cells of the cyanobacterium Synechococcus sp. PCC7942. We have shown previously that the light-harvesting phycobilisomes diffuse quite rapidly on the thylakoid membrane surface. However, the photosystem II core complexes appear completely immobile. This raises the possibility that all of the membrane integral protein complexes in the thylakoid membrane are locked into a rather rigid array. Alternatively, it is possible that photosystem II is specifically anchored in the membrane, with other membrane proteins able to diffuse around it. We have now resolved this question by studying the diffusion of a second integral membrane protein, the IsiA chlorophyll-binding protein. IsiA is induced under iron starvation and some other stress conditions. In iron-stressed cyanobacterial cells, a high proportion of chlorophyll fluorescence comes from IsiA. This makes it straightforward to examine the diffusion of IsiA by FRAP. We find that the complex is mobile with a mean diffusion coefficient of approximately 3 x 10(-11) cm(2) s(-1). Thus it is clear that some thylakoid membrane proteins are mobile and that there must be a specific anchor that prevents photosystem II diffusion. We discuss the implications for the structure and function of the cyanobacterial thylakoid membrane.
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Affiliation(s)
- Mary Sarcina
- Department of Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, United Kingdom
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30
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Mullineaux CW. FRAP analysis of photosynthetic membranes. JOURNAL OF EXPERIMENTAL BOTANY 2004; 55:1207-1211. [PMID: 15020635 DOI: 10.1093/jxb/erh106] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fluorescence Recovery after Photobleaching (FRAP) is a technique widely used in cell biology to observe the dynamics of biological systems, including the diffusion of membrane components. More information is needed on the dynamics of photosynthetic membranes in order to help to understand processes such as photosynthetic electron transport, regulation of light-harvesting, and biogenesis and turnover of the photosynthetic apparatus. FRAP has the potential to provide this information, although applying the technique to photosynthetic membranes is not always straightforward. This review explains the potential and the problems, and gives a brief guide to performing FRAP measurements and analysing the data.
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Affiliation(s)
- Conrad W Mullineaux
- Department of Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.
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31
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Helmreich EJM. Environmental influences on signal transduction through membranes: a retrospective mini-review. Biophys Chem 2003; 100:519-34. [PMID: 12646388 DOI: 10.1016/s0301-4622(02)00303-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This mini-review is addressed to the question how the membranous environment may affect traffic of receptors and signalling from membrane-anchored receptors on the outside of cells to transducers and targets on the inside. Signal transduction by membrane-anchored receptors to the interior of the cell and eventually to the genome is a central issue in cellular regulation. In this context the role of membrane fluidity and of the cytoskeleton in restricting the mobility of proteins are discussed and the evidence for a structural order in membranes which could limit the mobility of proteins is scrutinised.
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Affiliation(s)
- Ernst J M Helmreich
- Julius Maximilians Universität Würzburg, Werner von Siemensstrasse 83, D-97076 Würzburg, Germany.
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32
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Affiliation(s)
- Arnd Pralle
- Cell Biology and Biophysics Program, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
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33
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Abstract
The investigation of biomolecules has entered a new age since the development of methodologies capable of studies at the level of single molecules. In biology, most molecules show a complex dynamical behavior, with individual motions and transitions between different states occurring highly correlated in space and time within an arrangement of various elements. Recent advances in the development of new microscopy techniques with sensitivity at the single molecule have gained access to essentially new types of information obtainable from imaging biomolecular samples. These methodologies are described here in terms of their applicability to the in vivo detection and visualization of molecular processes on surfaces, membranes, and cells. First examples of single molecule microscopy on cell membranes revealed new basic insight into the lateral organization of the plasma membrane, providing the captivating perspective of an ultra-sensitive methodology as a general tool to study local processes and heterogeneities in living cells.
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Affiliation(s)
- G J Schütz
- Institute for Biophysics, University of Linz, Altenbergerstr. 69, A-4040 Linz, Austria.
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34
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Starr TE, Thompson NL. Fluorescence pattern photobleaching recovery for samples with multi-component diffusion. Biophys Chem 2002; 97:29-44. [PMID: 12052493 DOI: 10.1016/s0301-4622(02)00037-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The translational mobility of proteins and lipids in phospholipid bilayers is often not well described as ideal self diffusion. One of the best methods for characterizing such non-ideal diffusion is to use fluorescence pattern photobleaching recovery. In this method, the spatial gradient of the monitoring and bleaching intensity is created by using epi-fluorescence and an expanded Gaussian-shaped laser beam which passes though a Ronchi ruling placed at the back image plane of a microscope. A difficulty arises when the fluorescence recovery from the exchange of slowly diffusing molecules between illuminated and non-illuminated stripes temporally overlaps with the recovery from the exchange of more rapidly diffusing molecules through the gradient produced by the broad Gaussian shape of the illumination. In the work presented here, a general theory is developed that describes the shape of the resulting fluorescence recovery curve for these typical experimental conditions. Approximate expressions amenable to non-linear curve fitting are also given. The new theoretical formalism has been demonstrated on data for the translational mobility of a fluorescent lipid probe in phospholipid bilayers deposited on planar-fused silica substrates.
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Affiliation(s)
- Tammy E Starr
- Department of Chemistry, Campus Box 3290, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA
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35
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McElfresh M, Baesu E, Balhorn R, Belak J, Allen MJ, Rudd RE. Combining constitutive materials modeling with atomic force microscopy to understand the mechanical properties of living cells. Proc Natl Acad Sci U S A 2002; 99 Suppl 2:6493-7. [PMID: 11983924 PMCID: PMC128556 DOI: 10.1073/pnas.082520599] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2001] [Indexed: 01/17/2023] Open
Abstract
The goal of this work is to study the properties of living cells and cell membranes by using atomic force microscopy. During atomic force microscopy (AFM) measurement, there is a strong mechanical coupling between the AFM tip and the cell. The purpose of this paper is to present a model of the overall mechanical response of the cell that allows us to separate out the mechanical response of the cell from the local surface interactions we wish to quantify. These local interactions include recognition (or binding) events between molecules bound to an AFM tip (e.g., an antibody) and molecules or receptors on the cell surface (e.g., the respective antigen). The computational model differs from traditional Hertzian contact models by explicitly taking into account the mechanics of the biomembrane and cytoskeleton. The model also accounts for the mechanical response of the living cell during arbitrary deformation. The indentation of a bovine sperm cell is used to test the validity of this model, and further experiments are proposed to fully parameterize the model.
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Affiliation(s)
- Mike McElfresh
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
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36
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Faraudo J. Diffusion equation on curved surfaces. I. Theory and application to biological membranes. J Chem Phys 2002. [DOI: 10.1063/1.1456024] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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37
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Georgiou G, Bahra SS, Mackie AR, Wolfe CA, O'Shea P, Ladha S, Fernandez N, Cherry RJ. Measurement of the lateral diffusion of human MHC class I molecules on HeLa cells by fluorescence recovery after photobleaching using a phycoerythrin probe. Biophys J 2002; 82:1828-34. [PMID: 11916842 PMCID: PMC1301980 DOI: 10.1016/s0006-3495(02)75533-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The mobility of cell surface MHC class I molecules on HeLa cells was measured by fluorescence recovery after photobleaching (FRAP). The probe used for these studies was the phycobiliprotein R-phycoerythrin coupled to Fab fragments of a monoclonal antibody specific for human monomorphic MHC class I molecules. It was found that the recovery curves could be equally well fitted by either a random diffusion model with an immobile component or by an anomalous diffusion model. In the latter case, the anomalous diffusion exponent was consistent with that previously determined by single-particle tracking (SPT) experiments using the same probe (P. R. Smith, I. E. G. Morrison, K. M. Wilson, N. Fernandez, and R. J. Cherry. 1999. Biophys. J. 76:3331-3344). The FRAP experiments, however, yielded a considerably higher value of D(0), the diffusion coefficient for a time interval of 1 s. To determine whether the results were probe dependent, FRAP measurements were also performed with the same monoclonal antibody labeled with Oregon Green. These experiments gave similar results to those obtained with the phycoerythrin probe. FRAP experiments with the lipid probe 5-N-(octadecanoyl) aminofluoroscein (ODAF) bound to HeLa cells gave typical results for lipid diffusion. Overall, our observations and analysis are consistent with anomalous diffusion of MHC class I diffusion on HeLa cells, but quantitative differences between FRAP and SPT data remain to be explained.
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Affiliation(s)
- George Georgiou
- Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, United Kingdom
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38
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Kuśba J, Li L, Gryczynski I, Piszczek G, Johnson M, Lakowicz JR. Lateral diffusion coefficients in membranes measured by resonance energy transfer and a new algorithm for diffusion in two dimensions. Biophys J 2002; 82:1358-72. [PMID: 11867452 PMCID: PMC1301938 DOI: 10.1016/s0006-3495(02)75491-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We describe measurements of lateral diffusion in membranes using resonance energy transfer. The donor was a rhenium (Re) metal-ligand complex lipid, which displays a donor decay time near 3 micros. The long donor lifetime resulted in an ability to measure lateral diffusion coefficient below 10(-8) cm(2)/s. The donor decay data were analyzed using a new numerical algorithm for calculation of resonance energy transfer for donors and acceptors randomly distributed in two dimensions. An analytical solution to the diffusion equation in two dimensions is not known, so the equation was solved by the relaxation method in Laplace space. This algorithm allows the donor decay in the absence of energy transfer to be multiexponential. The simulations show that mutual lateral diffusion coefficients of the donor and acceptor on the order of 10(-8) cm(2)/s are readily recovered from the frequency-domain data with donor decay times on the microsecond timescale. Importantly, the lateral diffusion coefficients and acceptor concentrations can be recovered independently despite correlation between these parameters. This algorithm was tested and verified using the donor decays of a long lifetime rhenium lipid donor and a Texas red-lipid acceptor. Lateral diffusion coefficients ranged from 4.4 x 10(-9) cm(2)/s in 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG) at 10 degrees C to 1.7 x 10(-7) cm(2)/s in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) at 35 degrees C. These results demonstrated the possibility of direct measurements of lateral diffusion coefficients using microsecond decay time luminophores.
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Affiliation(s)
- Jósef Kuśba
- Technical University of Gdańsk, Faculty of Applied Physics and Mathematics, Gdansk, Poland
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39
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Sarcina M, Tobin MJ, Mullineaux CW. Diffusion of phycobilisomes on the thylakoid membranes of the cyanobacterium Synechococcus 7942. Effects of phycobilisome size, temperature, and membrane lipid composition. J Biol Chem 2001; 276:46830-4. [PMID: 11590154 DOI: 10.1074/jbc.m107111200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A variant of fluorescence recovery after photobleaching allows us to observe the diffusion of photosynthetic complexes in cyanobacterial thylakoid membranes in vivo. The unicellular cyanobacterium Synechococcus sp. PCC7942 is a wonderful model organism for fluorescence recovery after photobleaching, because it has a favorable membrane geometry and is well characterized and transformable. In Synechococcus 7942 (as in other cyanobacteria) we find that photosystem II is immobile, but phycobilisomes diffuse rapidly on the membrane surface. The diffusion coefficient is 3 x 10(-10) cm(2) s(-1) at 30 degrees C. This shows that the association of phycobilisomes with reaction centers is dynamic; there are no stable phycobilisome-reaction center complexes in vivo. We report the effects of mutations that change the phycobilisome size and membrane lipid composition. 1) In a mutant with no phycobilisome rods, the phycobilisomes remain mobile with a slightly faster diffusion coefficient. This confirms that the diffusion we observe is of intact phycobilisomes rather than detached rod elements. The faster diffusion coefficient in the mutant indicates that the rate of diffusion is partly determined by the phycobilisome size. 2) The temperature dependence of the phycobilisome diffusion coefficient indicates that the phycobilisomes have no integral membrane domain. It is likely that association with the membrane is mediated by multiple weak interactions with lipid head groups. 3) Changing the lipid composition of the thylakoid membrane has a dramatic effect on phycobilisome mobility. The results cannot be explained in terms of changes in the fluidity of the membrane; they suggest that lipids play a role in controlling phycobilisome-reaction center interaction.
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Affiliation(s)
- M Sarcina
- Department of Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, United Kingdom
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40
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Mackie AR, James PS, Ladha S, Jones R. Diffusion barriers in ram and boar sperm plasma membranes: directionality of lipid diffusion across the posterior ring. Biol Reprod 2001; 64:113-9. [PMID: 11133665 DOI: 10.1095/biolreprod64.1.113] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The plasma membrane of mammalian spermatozoa, like that of other differentiated cells, is compartmentalized into discrete regions or domains that are biochemically and functionally distinct from one another. Physical structures within the membrane, such as the posterior ring at the juncture of the sperm head and tail, have long been thought to act as diffusion barriers to help segregate important molecules required for fertilization within specific domains and to regulate migration of molecules between domains. In this investigation, we used a quantitative photobleaching technique (video-FRAP) to assess the efficacy of the posterior ring as a barrier to exchange of lipids between the postacrosomal and midpiece plasma membranes. A lipid reporter probe (1,1'-diduodecyl-3,3,3', 3'-tetramethylindocarbocyanine; DiIC(12)) was incorporated into the plasma membrane of live ram and boar spermatozoa, and the directionality of its diffusion across the posterior ring was measured by line-profile analysis. Results showed that DiIC(12) was able to traverse the posterior ring from the direction of the postacrosomal plasma membrane and to diffuse onto the midpiece plasma membrane. These results suggest that the posterior ring is not an immutable barrier to lipid exchange in mature spermatozoa and that there are other mechanisms for maintaining in-plane lipid asymmetry, such as differential phase behavior and interaction with the submembranous cytoskeleton.
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Affiliation(s)
- A R Mackie
- Department of Material Food Science, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, United Kingdom
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41
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Balakrishnan J. Spatial curvature effects on molecular transport by diffusion. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:4648-51. [PMID: 11088274 DOI: 10.1103/physreve.61.4648] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/1999] [Revised: 11/10/1999] [Indexed: 11/07/2022]
Abstract
For a substance diffusing on a curved surface, we obtain an explicit relation valid for very small values of the time, between the local concentration, the diffusion coefficient, the intrinsic spatial curvature, and the time. We recover the known solution of Fick's law of diffusion in the flat space limit. In the biological context, this result would be useful in understanding the variations in the diffusion rates of integral proteins and other molecules on membranes.
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Affiliation(s)
- J Balakrishnan
- Department of High Voltage Engineering, Indian Institute of Science, Bangalore, 560 012, India.
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Schütz GJ, Sonnleitner M, Hinterdorfer P, Schindler H. Single molecule microscopy of biomembranes (review). Mol Membr Biol 2000; 17:17-29. [PMID: 10824735 DOI: 10.1080/096876800294452] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Recent advances in the development of new microscopy techniques with a sensitivity of a single molecule have gained access to essentially new types of information obtainable from imaging biomolecular samples. These methodologies are analysed here in terms of their applicability to the in vivo visualization of cellular processes on the molecular scale, in particular of processes in cell membranes. First examples of single molecule microscopy on cell membranes revealed new basic insight into the lateral organization of the plasma membrane, providing the captivating perspective of an ultrasensitive methodology as a general tool to study local processes and heterogeneities in living cells.
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Affiliation(s)
- G J Schütz
- Institute for Biophysics, University of Linz, Austria
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43
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Sintes T, Baumgärtner A, Levine Y. Coarse-grained continuum model for molecular diffusion in a lipid monolayer. J Mol Liq 2000. [DOI: 10.1016/s0167-7322(99)00112-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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44
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Leitner DM, Brown FL, Wilson KR. Regulation of protein mobility in cell membranes: a dynamic corral model. Biophys J 2000; 78:125-35. [PMID: 10620280 PMCID: PMC1300624 DOI: 10.1016/s0006-3495(00)76579-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We analyze a two-state stochastic corral model for regulation of protein diffusion in a cell membrane. This model could mimic control of protein transport in the membrane by the cytoskeleton. The dynamic corral acts as a gate which when open permits an otherwise trapped protein to escape to a neighboring corral in the cytoskeletal network. We solve for the escape rate over a wide range of parameters of the model, and compare these results with Monte Carlo simulations. Upon introducing measured values of the model parameters for Band 3 in erythrocyte membranes, we are able to estimate the value for one unknown parameter, the average rate at which the corral closes. The ratio of calculated closing rate to measured opening rate is roughly 100:1, consistent with a gating mechanism whereby protein mobility is regulated by dissociation and reassociation of segments of the cytoskeletal network.
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Affiliation(s)
- D M Leitner
- UCSD Department of Chemistry, La Jolla, California 92093-0339 USA.
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45
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Roberts RL, Barbieri MA, Pryse KM, Chua M, Morisaki JH, Stahl PD. Endosome fusion in living cells overexpressing GFP-rab5. J Cell Sci 1999; 112 ( Pt 21):3667-75. [PMID: 10523503 DOI: 10.1242/jcs.112.21.3667] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CHO and BHK cells which overexpress either wild-type rab5 or rab5:Q79L, a constitutively active rab5 mutant, develop enlarged cytoplasmic vesicles that exhibit many characteristics of early endosomes including immunoreactivity for rab5 and transferrin receptor. Time-lapse video microscopy shows the enlarged endosomes arise primarily by fusion of smaller vesicles. These fusion events occur mostly by a ‘bridge’ fusion mechanism in which the initial opening between vesicles does not expand; instead, membrane flows slowly and continuously from the smaller to the larger endosome in the fusing pair, through a narrow, barely perceptible membranous ‘bridge’ between them. The unique aspect of rab5 mediated ‘bridge’ fusion is the persistence of a tight constriction at the site where vesicles merge and we hypothesize that this constriction results from the relatively slow disassembly of a putative docking/fusion complex. To determine the relation of rab5 to the fusion ‘bridge’, we used confocal fluorescence microscopy to monitor endosome fusion in cells overexpressing GFP-rab5 fusion proteins. Vesicle docking in these cells is accompanied by recruitment of the GFP-rab5 into a brightly fluorescent spot in the ‘bridge’ region between fusing vesicles that persists throughout the entire length of the fusion event and which often persist for minutes following endosome fusion. Other endosomal membrane markers, including FM4-64, are not concentrated in fusion ‘bridges’. These results support the idea that the GFP-rab5 spots represent the localized accumulation of GFP-rab5 between fusing endosomes and not simply overlap of adjacent membranes. The idea that the GFP-rab5 spots do not represent membrane overlap is further supported by experiments using photobleaching techniques and confocal imaging which show that GFP-rab5 localized in spots between fusion couplets is resistant to diffusion while GFP-rab5 on endosomal membranes away from these spots rapidly diffuses with a rate constant of about 1.0 (+/-0.3) x10(-)(9)cm(2)/second.
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Affiliation(s)
- R L Roberts
- Department of Cell Biology and Physiology and Biochemistry and Molecular Biophysics, Washington University, School of Medicine, St Louis, MO 63110, USA
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46
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Sintes T, Baumgaertner A, Levine YK. Translational diffusion of flexible lipid chains in a Langmuir monolayer: a dynamic Monte Carlo study. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 60:814-20. [PMID: 11969823 DOI: 10.1103/physreve.60.814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/1998] [Revised: 03/18/1999] [Indexed: 04/18/2023]
Abstract
We report a computer simulation study of the lateral diffusion of conformationally disordered lipid molecules in a monolayer structure. The simulations were carried out with dynamic Monte Carlo methods, employing two different representations of the internal motions of the lipid chains. The classical Cohen-Turnbull theory is found to provide a good description of the simulated lateral diffusion coefficients at moderate densities. The substantial deviations found at low densities are attributed to the small density fluctuations needed to create the free volume required for the lateral diffusion process.
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Affiliation(s)
- T Sintes
- Forum Modelierung, Forschungszentrum Jülich, 52425 Jülich, Germany
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47
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Smith PR, Morrison IE, Wilson KM, Fernández N, Cherry RJ. Anomalous diffusion of major histocompatibility complex class I molecules on HeLa cells determined by single particle tracking. Biophys J 1999; 76:3331-44. [PMID: 10354459 PMCID: PMC1300303 DOI: 10.1016/s0006-3495(99)77486-2] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Single-particle tracking (SPT) was used to determine the mobility characteristics of MHC (major histocompatibility complex) class I molecules at the surface of HeLa cells at 22 degrees C and on different time scales. MHC class I was labeled using the Fab fragment of a monoclonal antibody (W6/32), covalently bound to either R-phycoerythrin or fluorescent microspheres, and the particles were tracked using high-sensitivity fluorescence imaging. Analysis of the data for a fixed time interval suggests a reasonable fit to a random diffusion model. The best fit values of the diffusion coefficient D decreased markedly, however, with increasing time interval, demonstrating the existence of anomalous diffusion. Further analysis of the data shows that the diffusion is anomalous over the complete time range investigated, 4-300 s. Fitting the results obtained with the R-phycoerythrin probe to D = D0talpha-1, where Do is a constant and t is the time, gave D0 = (6.7 +/- 4.5) x 10(-11) cm2 s-1 and alpha = 0.49 +/- 0.16. Experiments with fluorescent microspheres were less reproducible and gave slower anomalous diffusion. The R-phycoerythrin probe is considered more reliable for fluorescent SPT because it is small (11 x 8 nm) and monovalent. The type of motion exhibited by the class I molecules will greatly affect their ability to migrate in the plane of the membrane. Anomalous diffusion, in particular, greatly reduces the distance a class I molecule can travel on the time scale of minutes. The present data are discussed in relation to the possible role of diffusion and clustering in T-cell activation.
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Affiliation(s)
- P R Smith
- Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, England
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48
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Abstract
Two dimensional motion of membrane receptors provides a mechanism for interaction among receptors in the plane of the membrane. In some cases the lateral diffusion leads to formation of clusters which may also be mobile. We have used image cross-correlation (ICCS) spectroscopy technique to measure the translational motion of transferrin receptors in the membrane of 3T3 fibroblasts and HEp2 carcinoma cells. The technique is based on the measurement and analysis of fluctuations in the intensity observed in fluorescence confocal microscope images measured as a function of time. The fluorescence fluctuations arise from stochastic concentration fluctuations about the equilibrium concentration caused by movement of receptors. The amplitude of the fluctuations depend on the number of fluorescent molecules in the observation volume and the dynamics provide the rate of movement. The diffusion observed by this analysis is orders of magnitude slower than that measured by conventional photobleaching techniques. The slower motion corresponds to the diffusion of receptor clusters which provide the more dominant fluctuations.
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Affiliation(s)
- M Srivastava
- Department of Chemistry, University of Western Ontario, London, Canada
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49
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Wolfe CA, James PS, Mackie AR, Ladha S, Jones R. Regionalized lipid diffusion in the plasma membrane of mammalian spermatozoa. Biol Reprod 1998; 59:1506-14. [PMID: 9828199 DOI: 10.1095/biolreprod59.6.1506] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The plasma membrane of mammalian spermatozoa shows pronounced lateral asymmetry with many glycoproteins restricted to specific domains. Some of these antigens are freely diffusing throughout the membrane whereas others appear static in position. It is not clear whether these concepts also apply to membrane lipids. In this investigation we have used fluorescence recovery after photobleaching (FRAP) techniques to spatially resolve lipid dynamics in various surface domains of 5 species of mammalian spermatozoa (bull, boar, ram, mouse, and guinea pig). Sperm plasma membranes were loaded with 5-(N-octadecanoyl)aminofluorescein (ODAF) reporter probe, and its diffusion was measured in various domains by FRAP analysis. Results showed that in live bull, boar, ram, and mouse spermatozoa, diffusion coefficients (D) were significantly higher over the acrosome and postacrosome than on the midpiece and principal piece of the tail. In dead or permeabilized cells, on the other hand, large immobile phases developed, particularly on the sperm tail, that severely reduced D values. ODAF diffusion was also sensitive to temperature and cross-linking of protein components within the membrane with paraformaldehyde. Guinea pig spermatozoa were different in almost all respects from those of the other species tested. It is concluded that lipid diffusion in the plasma membrane of live spermatozoa varies significantly between surface domains, because of either compositional heterogeneity, or differences in bilayer disposition, or the presence of intramembranous barriers that impede free exchange between domains. This study emphasizes the important role of membrane lipids in regulating polarized migration of sperm surface antigens during developmental processes such as maturation and capacitation.
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Affiliation(s)
- C A Wolfe
- Department of Food Biophysics, Institute of Food Research, Colney, Norwich NR4 7UA, United Kingdom
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50
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Simson R, Yang B, Moore SE, Doherty P, Walsh FS, Jacobson KA. Structural mosaicism on the submicron scale in the plasma membrane. Biophys J 1998; 74:297-308. [PMID: 9449330 PMCID: PMC1299382 DOI: 10.1016/s0006-3495(98)77787-2] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The lateral mobility of the neural cell adhesion molecule (NCAM) was examined using single particle tracking (SPT). Various isoforms of human NCAM, differing in their ectodomain, their membrane anchorage mode, or the size of their cytoplasmic domain, were expressed in National Institutes of Health 3T3 cells and C2C12 muscle cells. On a 6.6-s time scale, SPT measurements on both transmembrane and glycosylphosphatidylinositol (GPI) anchored isoforms of NCAM expressed in 3T3 cells could be classified into mobile (Brownian diffusion), slow diffusion, corralled diffusion, and immobile subpopulations. On a 90-s time scale, SPT studies in C2C12 cells revealed that 40-60% of transfected NCAM was mobile, whereas a smaller fraction (approximately 10-30%) experienced much slower diffusion. In addition, a fraction of approximately 30% of both transfected GPI and transmembrane isoforms and endogenous NCAM isoforms in C2C12 cells experienced transient confinement for approximately 8 s within regions of approximately 300-nm diameter. Diffusion within both these and the slow diffusion regions was anomalous, consistent with movements through a dense field of obstacles, whereas diffusion outside these regions was normal. Thus the membrane appears as a mosaic containing regions that permit free diffusion as well as regions in which NCAM is transiently confined to small or more extended domains. These results, including a large, freely diffusing fraction, similar confinement of transmembrane and GPI isoforms, a significant slowly diffusing fraction, and relatively large interdomain distances, are at some variance with the membrane skeleton fence model (Kusumi and Sako, 1996). Possible revisions to the model that incorporate these data are discussed.
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Affiliation(s)
- R Simson
- Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599, USA
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