Formalizing Spherical Membrane Structures and Membrane Proteins Populations

2006 ◽  
pp. 18-41 ◽  
Author(s):  
Daniela Besozzi ◽  
Grzegorz Rozenberg
Keyword(s):  
Membrane Proteins ◽  
Membrane Structures

scholarly journals Membrane recruitment of Atg8 by Hfl1 facilitates turnover of vacuolar membrane proteins in yeast cells approaching stationary phase

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Cheng-Wen He ◽  
Xue-Fei Cui ◽  
Shao-Jie Ma ◽  
Qin Xu ◽  
Yan-Peng Ran ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Stationary Phase ◽  
Molecular Mechanisms ◽  
Multivesicular Body ◽  
Degradation Process ◽  
Vacuolar Membrane ◽  
Yeast Cells ◽  
Membrane Structures ◽  
Membrane Recruitment

Abstract Background The vacuole/lysosome is the final destination of autophagic pathways, but can also itself be degraded in whole or in part by selective macroautophagic or microautophagic processes. Diverse molecular mechanisms are involved in these processes, the characterization of which has lagged behind those of ATG-dependent macroautophagy and ESCRT-dependent endosomal multivesicular body pathways. Results Here we show that as yeast cells gradually exhaust available nutrients and approach stationary phase, multiple vacuolar integral membrane proteins with unrelated functions are degraded in the vacuolar lumen. This degradation depends on the ESCRT machinery, but does not strictly require ubiquitination of cargos or trafficking of cargos out of the vacuole. It is also temporally and mechanistically distinct from NPC-dependent microlipophagy. The turnover is facilitated by Atg8, an exception among autophagy proteins, and an Atg8-interacting vacuolar membrane protein, Hfl1. Lack of Atg8 or Hfl1 led to the accumulation of enlarged lumenal membrane structures in the vacuole. We further show that a key function of Hfl1 is the membrane recruitment of Atg8. In the presence of Hfl1, lipidation of Atg8 is not required for efficient cargo turnover. The need for Hfl1 can be partially bypassed by blocking Atg8 delipidation. Conclusions Our data reveal a vacuolar membrane protein degradation process with a unique dependence on vacuole-associated Atg8 downstream of ESCRTs, and we identify a specific role of Hfl1, a protein conserved from yeast to plants and animals, in membrane targeting of Atg8.

scholarly journals Identification of detergent-resistant plasma membrane microdomains in dictyostelium: enrichment of signal transduction proteins.

1997 ◽  
Vol 8 (5) ◽  
pp. 855-869 ◽  
Author(s):  
Z Xiao ◽  
P N Devreotes
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Cell Surface ◽  
G Protein ◽  
Biochemical Characterization ◽  
Surface Membrane ◽  
Actin Binding ◽  
Membrane Microdomains ◽  
Immunogold Electron Microscopy ◽  
Membrane Structures

Unlike most other cellular proteins, the chemoattractant receptor, cAR1, of Dictyostelium is resistant to extraction by the zwitterionic detergent, CHAPS. We exploited this property to isolate a subcellular fraction highly enriched in cAR1 by flotation of CHAPS lysates of cells in sucrose density gradients. Immunogold electron microscopy studies revealed a homogeneous preparation of membrane bilayer sheets. This preparation, designated CHAPS-insoluble floating fraction (CHIEF), also contained a defined set of 20 other proteins and a single uncharged lipid. Cell surface biotinylation and preembedding immunoelectron microscopy both confirmed the plasma membrane origin of this preparation. The cell surface phosphodiesterase (PDE) and a downstream effector of cAR1, adenylate cyclase (ACA), were specifically localized in these structures, whereas the cell adhesion molecule gp80, most of the major cell surface membrane proteins, cytoskeletal components, the actin-binding integral membrane protein ponticulin, and G-protein alpha- and beta-subunits were absent. Overall, CHIFF represents about 3-5% of cell externally exposed membrane proteins. All of these results indicate that CHIFF is derived from specialized microdomains of the plasma membrane. The method of isolation is analogous to that of caveolae. However, we were unable to detect distinct caveolae-like structures on the cell surface associated with cAR1, which showed a diffuse staining profile. The discovery of CHIFF facilitates the purification of cAR1 and related signaling proteins and the biochemical characterization of receptor-mediated processes such as G-protein activation and desensitization. It also has important implications for the "fluid mosaic" model of the plasma membrane structures.

scholarly journals Pentanol and Benzyl Alcohol Attack Bacterial Surface Structures Differently

2015 ◽  
Vol 82 (1) ◽  
pp. 402-408 ◽  
Author(s):  
Takehisa Yano ◽  
Yoshiko Miyahara ◽  
Noriyuki Morii ◽  
Tetsuya Okano ◽  
Hiromi Kubota
Keyword(s):  
Membrane Proteins ◽  
Benzyl Alcohol ◽  
Efflux Pump ◽  
Public Health Issue ◽  
Membrane Structures ◽  
Giant Vesicles ◽  
Content Type ◽  
Cellular Accumulation ◽  
Bacterial Surface ◽  
Membrane Fluidization

ABSTRACTThe genusMethylobacteriumtolerates hygiene agents like benzalkonium chloride (BAC), and infection with this organism is an important public health issue. Here, we found that the combination of BAC with particular alcohols at nonlethal concentrations in terms of their solitary uses significantly reduced bacterial viability after only 5 min of exposure. Among the alcohols, Raman spectroscopic analyses showed that pentanol (pentyl alcohol [PeA]) and benzyl alcohol (BzA) accelerated the cellular accumulation of BAC. Fluorescence spectroscopic assays and morphological assays with giant vesicles indicated that PeA rarely attacked membrane structures, while BzA increased the membrane fluidity and destabilized the structures. Other fluorescent spectroscopic assays indicated that PeA and BzA inactivate bacterial membrane proteins, including an efflux pump for BAC transportation. These findings suggested that the inactivation of membrane proteins by PeA and BzA led to the cellular accumulation but that only BzA also enhanced BAC penetration by membrane fluidization at nonlethal concentrations.

scholarly journals Human Pex19p Binds Peroxisomal Integral Membrane Proteins at Regions Distinct from Their Sorting Sequences

2001 ◽  
Vol 21 (13) ◽  
pp. 4413-4424 ◽  
Author(s):  
Marc Fransen ◽  
Tine Wylin ◽  
Chantal Brees ◽  
Guy P. Mannaerts ◽  
Paul P. Van Veldhoven
Keyword(s):  
Membrane Proteins ◽  
Important Determinant ◽  
Integral Membrane Proteins ◽  
Alternative View ◽  
Membrane Biogenesis ◽  
Soluble Receptor ◽  
Membrane Structures ◽  
Peroxisomal Membrane ◽  
Binding Domains ◽  
Molecular Machinery

ABSTRACT The molecular machinery underlying peroxisomal membrane biogenesis is not well understood. The observation that cells deficient in the peroxins Pex3p, Pex16p, and Pex19p lack peroxisomal membrane structures suggests that these molecules are involved in the initial stages of peroxisomal membrane formation. Pex19p, a predominantly cytosolic protein that can be farnesylated, binds multiple peroxisomal integral membrane proteins, and it has been suggested that it functions as a soluble receptor for the targeting of peroxisomal membrane proteins (PMPs) to the peroxisome. An alternative view proposes that Pex19p functions as a chaperone at the peroxisomal membrane. Here, we show that the peroxisomal sorting determinants and the Pex19p-binding domains of a number of PMPs are distinct entities. In addition, we extend the list of peroxins with which human Pex19p interacts to include the PMP Pex16p and show that Pex19p's CaaX prenylation motif is an important determinant in the affinity of Pex19p for Pex10p, Pex11pβ, Pex12p, and Pex13p.

Escherichia colias an expression system for K+transport systems from plants

2001 ◽  
Vol 281 (3) ◽  
pp. C733-C739 ◽  
Author(s):  
Nobuyuki Uozumi
Keyword(s):  
Membrane Proteins ◽  
Expression System ◽  
Functional Expression ◽  
Host Cells ◽  
Transport Systems ◽  
Membrane Structures ◽  
E Coli ◽  
Escherichia Coli Expression ◽  
Experimental Findings ◽  
And Function

The value of the Escherichia coli expression system has long been established because of its effectiveness in characterizing the structure and function of exogenously expressed proteins. When eukaryotic membrane proteins are functionally expressed in E. coli, this organism can serve as an alternative to eukaryotic host cells. A few examples have been reported of functional expression of animal and plant membrane proteins in E. coli. This mini-review describes the following findings: 1) homologous K+transporters exist in prokaryotic cells and in eukaryotic cells; 2) plant K+transporters can functionally complement mutant K+transporter genes in E. coli; and 3) membrane structures of plant K+transporters can be elucidated in an E. colisystem. These experimental findings suggest the possibility of utilizing the E. coli bacterium as an expression system for other eukaryotic membrane transport proteins.

scholarly journals Yarrowia lipolyticaCells Mutant for thePEX24Gene Encoding a Peroxisomal Membrane Peroxin Mislocalize Peroxisomal Proteins and Accumulate Membrane Structures Containing Both Peroxisomal Matrix and Membrane Proteins

2002 ◽  
Vol 13 (8) ◽  
pp. 2681-2691 ◽  
Author(s):  
Yuen Yi C. Tam ◽  
Richard A. Rachubinski
Keyword(s):  
Oleic Acid ◽  
Membrane Proteins ◽  
Integral Membrane Protein ◽  
Open Reading Frames ◽  
The Novel ◽  
Wild Type ◽  
Membrane Structures ◽  
Peroxisomal Membrane ◽  
High Sequence Homology ◽  
Reading Frames

Peroxins are proteins required for peroxisome assembly and are encoded by the PEX genes. Functional complementation of the oleic acid–nonutilizing strain mut1-1 of the yeastYarrowia lipolytica has identified the novel gene,PEX24. PEX24 encodes Pex24p, a protein of 550 amino acids (61,100 Da). Pex24p is an integral membrane protein of peroxisomes that exhibits high sequence homology to two hypothetical proteins encoded by the open reading frames YHR150W andYDR479C of the Saccharomyces cerevisiaegenome. Pex24p is detectable in wild-type cells grown in glucose-containing medium, and its levels are significantly increased by incubation of cells in oleic acid–containing medium, the metabolism of which requires intact peroxisomes. pex24 mutants are compromised in the targeting of both matrix and membrane proteins to peroxisomes. Although pex24 mutants fail to assemble functional peroxisomes, they do harbor membrane structures that contain subsets of peroxisomal proteins.

Changes Occur in Plasma Membrane Turnover when K562 Leukemia Cells are Induced to Differentiate

1982 ◽  
Vol 40 ◽  
pp. 286-287
Author(s):  
L. M. Marshall
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Intracellular Transport ◽  
Parent Cell ◽  
Membrane Turnover ◽  
Coated Pits ◽  
Surface Distribution ◽  
Specific Proteins ◽  
Erythroleukemic Cell ◽  
Specific Membrane

A human erythroleukemic cell line, metabolically blocked in a late stage of erythropoiesis, becomes capable of differentiation along the normal pathway when grown in the presence of hemin. This process is characterized by hemoglobin synthesis followed by rearrangement of the plasma membrane proteins and culminates in asymmetrical cytokinesis in the absence of nuclear division. A reticulocyte-like cell buds from the nucleus-containing parent cell after erythrocyte specific membrane proteins have been sequestered into its membrane. In this process the parent cell faces two obstacles. First, to organize its erythrocyte specific proteins at one pole of the cell for inclusion in the reticulocyte; second, to reduce or abolish membrane protein turnover since hemoglobin is virtually the only protein being synthesized at this stage. A means of achieving redistribution and cessation of turnover could involve movement of membrane proteins by a directional lipid flow. Generation of a lipid flow towards one pole and accumulation of erythrocyte-specific membrane proteins could be achieved by clathrin coated pits which are implicated in membrane endocytosis, intracellular transport and turnover. In non-differentiating cells, membrane proteins are turned over and are random in surface distribution. If, however, the erythrocyte specific proteins in differentiating cells were excluded from endocytosing coated pits, not only would their turnover cease, but they would also tend to drift towards and collect at the site of endocytosis. This hypothesis requires that different protein species are endocytosed by the coated vesicles in non-differentiating than by differentiating cells.

Image Analysis of Intramembrane Particles in Freeze-Fractured Biomembranes Using Computer Simulation Techniques

1975 ◽  
Vol 33 ◽  
pp. 214-215
Author(s):  
D.J. Benefiel ◽  
R.S. Weinstein
Keyword(s):  
Membrane Proteins ◽  
Freeze Fracture ◽  
Integral Membrane Proteins ◽  
Systematic Evaluation ◽  
Intramembrane Particles ◽  
Modeling Methods ◽  
Simulation Techniques ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron ◽  
Computer Simulation Techniques

Intramembrane particles (IMP or MAP) are components of most biomembranes. They are visualized by freeze-fracture electron microscopy, and they probably represent replicas of integral membrane proteins. The presence of MAP in biomembranes has been extensively investigated but their detailed ultrastructure has been largely ignored. In this study, we have attempted to lay groundwork for a systematic evaluation of MAP ultrastructure. Using mathematical modeling methods, we have simulated the electron optical appearances of idealized globular proteins as they might be expected to appear in replicas under defined conditions. By comparing these images with the apearances of MAPs in replicas, we have attempted to evaluate dimensional and shape distortions that may be introduced by the freeze-fracture technique and further to deduce the actual shapes of integral membrane proteins from their freezefracture images.

A Novel Reconstitution Method for Inducing the Formation of Regular 2-Dimensional Arrays of Membrane Proteins and Lipids

1988 ◽  
Vol 46 ◽  
pp. 152-153 ◽  
Author(s):  
A. Engel ◽  
A. Holzenburg ◽  
K. Stauffer ◽  
J. Rosenbusch ◽  
U. Aebi
Keyword(s):  
Membrane Proteins ◽  
Flow Rate ◽  
Lipid Membranes ◽  
Functional Characterization ◽  
Dimensional Structure ◽  
Electron Crystallography ◽  
Peltier Element ◽  
Protein Ratio ◽  
Precise Control ◽  
3 Dimensional

Reconstitution of solubilized and purified membrane proteins in the presence of phospholipids into vesicles allows their functions to be studied by simple bulk measurements (e.g. diffusion of differently sized solutes) or by conductance measurements after transformation into planar membranes. On the other hand, reconstitution into regular protein-lipid arrays, usually forming at a specific lipid-to-protein ratio, provides the basis for determining the 3-dimensional structure of membrane proteins employing the tools of electron crystallography.To refine reconstitution conditions for reproducibly inducing formation of large and highly ordered protein-lipid membranes that are suitable for both electron crystallography and patch clamping experiments aimed at their functional characterization, we built a flow-dialysis device that allows precise control of temperature and flow-rate (Fig. 1). The flow rate is generated by a peristaltic pump and can be adjusted from 1 to 500 ml/h. The dialysis buffer is brought to a preselected temperature during its travel through a meandering path before it enters the dialysis reservoir. A Z-80 based computer controls a Peltier element allowing the temperature profile to be programmed as function of time.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

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