Membrane Proteins:
Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.
JoVE General
Crystallizing Membrane Proteins for Structure Determination using Lipidic Mesophases
Herein is described the procedure implemented in the Caffrey Membrane Structural and Functional Biology Group to set up manually crystallization trials of membrane proteins in lipidic mesophases.
JoVE General
Use of a Robot for High-throughput Crystallization of Membrane Proteins in Lipidic Mesophases
Herein is described a robotic approach to high-throughput crystallization of membrane proteins in lipidic mesophases for use in structure determination using macromolecular X-ray crystallography. Three robots capable of handling the viscous and sticky protein-laden mesophase integral to the method are introduced.
JoVE General
A Step-by-step Method for the Reconstitution of an ABC Transporter into Nanodisc Lipid Particles
Department of Biochemistry and Molecular Biology, University of British Columbia
Nanodiscs are small discoid particles that incorporate membrane proteins into a small patch of phospholipid bilayer. We provide a visual protocol that shows the step-by-step incorporation of the MalFGK2 transporter into a disc.
JoVE General
Method for the Isolation of Francisella tularensis Outer Membranes
Department of Microbiology, University of Texas Southwestern Medical Center
A protocol for separating inner and outer membranes from Francisella tularensis by spheroplasting, osmotic lysis, and sucrose density gradient ultracentrifugation.
JoVE General
Crystallization of Membrane Proteins in Lipidic Mesophases
Molecular Biology, The Scripps Research Institute
The protocols describe the essential steps for obtaining diffraction quality crystals of a membrane protein starting from reconstitution of the protein in a lipidic cubic phase (LCP), finding initial conditions with LCP-FRAP pre-crystallization assays, setting up LCP crystallization trials and harvesting crystals.
JoVE Bioengineering
Thermodynamics of Membrane Protein Folding Measured by Fluorescence Spectroscopy
Chemistry and Biochemistry, University of California San Diego - UCSD
This video article details the experimental procedure for obtaining the Gibbs free energy of membrane protein folding by tryptophan fluorescence.
JoVE General
Probing for Mitochondrial Complex Activity in Human Embryonic Stem Cells
David Geffen School of Medicine, University of California, Los Angeles
In this video, we will show you how the mitochondrial respiratory chain complexes of human embryonic stem cells can be analyzed using in gel activity assays.
JoVE General
Introduction to Solid Supported Membrane Based Electrophysiology
1Department of Biophysical Chemistry, Max Planck Institute of Biophysics, 2Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt
Here we present an electrophysiological method based on solid supported membranes with focus on its applications for the characterization of electrogenic membrane transporters.
JoVE General
Split-Ubiquitin Based Membrane Yeast Two-Hybrid (MYTH) System: A Powerful Tool For Identifying Protein-Protein Interactions
1Department of Biochemistry, University of Toronto, 2Department of Molecular Genetics, University of Toronto, 3Terrence Donnelly Centre for Cellular and Biomolecular Research (CCBR), University of Toronto
MYTH allows the sensitive detection of transient and stable interactions between proteins that are expressed in the model organism Saccharomyces cerevisiae. It has been successfully applied to study exogenous and yeast integral membrane proteins in order to identify their interacting partners in a high throughput manner.
JoVE General
Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties
Department of Physiology and Biophysics, Weill Cornell Medical College
We introduce a fast fluorescence-based assay that monitors the rate of fluorescence quenching as a measure of gramicidin channel activity. The gramicidin channels are used as molecular force transducers to monitor changes in lipid bilayer properties as sensed by bilayer spanning proteins.
JoVE General
High-throughput Crystallization of Membrane Proteins Using the Lipidic Bicelle Method
1UCLA-DOE Institute for Genomics and Proteomics, University of California Los Angeles, 2Department of Physiology, David Geffen School of Medicine, UCLA
Bicelles are lipid/amphiphile mixtures that maintain membrane proteins (MPs) within a lipid bilayer but have unique phase behavior that facilitates high-throughput screening by crystallization robots. This technique has successfully produced a number of high-resolution structures from both prokaryotic and eukaryotic sources. This video describes protocols for generating the lipidic bicelle mixture, incorporating MPs into the bicelle mixture, setting up crystallizations trials (manually as well as robotically) and harvesting crystals from the medium.
JoVE General
Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography
Herein is described procedures implemented in the Caffrey Membrane Structural and Functional Biology Group to harvest and cryo-cool membrane protein crystals grown in lipidic cubic and sponge phases for use in structure determination using macromolecular X-ray crystallography.
JoVE Immunology and Infection
Immuno-fluorescence Assay of Leptospiral Surface-exposed Proteins
1Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 2Research service, 151, Veterans Affairs Greater Los Angeles Healthcare System, 3Departments of Medicine, Urology at David Geffen School of Medicine and Department of Microbiology, Immunology and Molecular Gentics, University of California Los Angeles (UCLA), 4Division of Infectious Diseases, 111F, Veterans Affairs Greater Los Angeles Health Care System
An efficient method to assess surface-exposure of leptospiral proteins is described. The method is specifically designed to avoid disruption of the fragile outer membrane of leptospiral cells. This technique requires employment of several negative controls to assess the integrity of the outer membrane and specificity of antibody reaction.
JoVE General
Assessing Two-dimensional Crystallization Trials of Small Membrane Proteins for Structural Biology Studies by Electron Crystallography
1School of Biology, Georgia Institute of Technology, 2Department of Molecular Pharmacology, RWTH Aachen University, 3School of Chemistry and Biochemistry, Georgia Institute of Technology
Evaluating two-dimensional (2D) crystallization trials for the formation of ordered membrane protein arrays is a highly critical and difficult task in electron crystallography. Here we describe our approach in screening for and identifying 2D crystals of predominantly small membrane proteins in the range of 15 – 90kDa.
JoVE General
Measuring Plasma Membrane Protein Endocytic Rates by Reversible Biotinylation
University of Massachusetts Medical School
Regulated endocytosis governs the cell surface expression levels of the majority of membrane proteins. Here we utilize reducible, membrane impermeant biotinylation reagents to measure the endocytic rate of the dopamine transporter (DAT), a polytopic membrane protein. The method facilitates a straightforward approach to measuring the endocytic rate of most plasma membrane proteins.
JoVE General
Analysis of SNARE-mediated Membrane Fusion Using an Enzymatic Cell Fusion Assay
Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine
We have developed a cell fusion assay that quantifies SNARE-mediated membrane fusion events by activated expression of β-galactosidase.
JoVE General
Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry
1Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, 2Deparment of Biochemistry, Research and Innovation Centre, University of Regina, 3Department of Medical Genetics and Microbiology, University of Toronto
Affinity purification of tagged proteins in combination with mass spectrometry (APMS) is a powerful method for the systematic mapping of protein interaction networks and for investigating the mechanistic basis of biological processes. Here, we describe an optimized sequential peptide affinity (SPA) APMS procedure developed for the bacterium Escherichia coli that can be used to isolate and characterize stable multi-protein complexes to near homogeneity even starting from low copy numbers per cell.
JoVE General
Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Department of Chemistry and Biochemistry, University of Colorado at Boulder
An efficient procedure to assess the oligomerization propensity of single-pass transmembrane domains (TMDs) is described. Chimeric proteins consisting of the TMD fused to ToxR are expressed in an E. coli reporter strain. TMD-induced oligomerization causes dimerization of ToxR, activation of transcription and production of the reporter protein, -galactosidase.
JoVE General
Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Department of Chemistry and Biochemistry, Worcester Polytechnic Institute
We will describe a method which measures the kinetics of ion transport of membrane proteins alongside site-specific analysis of conformational changes using fluorescence on single cells. This technique is adaptable to ion channels, transporters and ion pumps and can be utilized to determine distance constraints between protein subunits.
JoVE Chemistry
Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies
1Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, 2The University of Melbourne
Biophysical and biochemical studies of interactions among membrane-embedded protein domains face many technical challenges, the first of which is obtaining appropriate study material. This article describes a protocol for producing and purifying disulfide-stabilized transmembrane peptide complexes that are suitable for structural analysis by solution nuclear magnetic resonance (NMR) and other analytical applications.
JoVE Bioengineering
High-throughput Protein Expression Generator Using a Microfluidic Platform
We present a microfluidic approach for the expression of protein arrays. The device consists of thousands of reaction chambers controlled by micro-mechanical valves. The microfluidic device is mated to a microarray-printed gene library. These genes are then transcribed and translated on-chip, resulting in a protein array ready for experimental use.
JoVE General
Single Molecule Methods for Monitoring Changes in Bilayer Elastic Properties
1Department of Physiology and Biophysics, Weill Cornell Medical College, 2Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell University
Membrane protein function is regulated by the cell membrane lipid composition. This video-article details how to form a patch using bilayer patch electrodes, as well as how to use gramicidin channels as reporters of altered membrane properties.
JoVE Neuroscience
Lateral Diffusion and Exocytosis of Membrane Proteins in Cultured Neurons Assessed using Fluorescence Recovery and Fluorescence-loss Photobleaching
MRC Centre for Synaptic Plasticity, University of Bristol
This report describes the use of live cell imaging and photobleach techniques to determine the surface expression, transport pathways and trafficking kinetics of exogenously expressed, pH-sensitive GFP-tagged proteins at the plasma membrane of neurons.
JoVE General
MALDI Sample Preparation: the Ultra Thin Layer Method
Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, Rockefeller University
This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS).
JoVE General
Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein
Department of Biological Sciences, University of Illinois Chicago - UIC
In this protocol we demonstrate the expression, solubilization, and purification of a recombinantly expressed membrane protein, MexB, as a soluble protein detergent complex. MexB is a multidrug resistance membrane transporter from the opportunistic bacterial pathogen Pseudomonas aeruginosa.
JoVE General
Isolation of Labile Multi-protein Complexes by in vivo Controlled Cellular Cross-Linking and Immuno-magnetic Affinity Chromatography
1Department of Cell Biology, Emory University, 2Department of Medicine, Division of Cardiology, Emory University
The cell permeable crosslinker DSP [dithiobis-(succinimidyl propionate)] stabilizes transient and labile interactions in vivo, which allows their isolation using stringent protein complex purification techniques. Here we present a technique for crosslinking cells grown in culture followed by isolation of protein complexes by immunoprecipitation.
JoVE General
Mutagenesis and Analysis of Genetic Mutations in the GC-rich KISS1 Receptor Sequence Identified in Humans with Reproductive Disorders
1Division of Endocrinology and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, 2Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine
Mutations in the kisspeptin receptor (KISS1R) are associated with reproductive disorders in patients. Here we describe how to introduce mutations of interest in the GC-rich sequence of KISS1R as well as the use of KISS1R constructs to characterize the degradation pathway of the receptor by immunoprecipitation and western blot.
JoVE General
Blue Native Polyacrylamide Gel Electrophoresis (BN-PAGE) for Analysis of Multiprotein Complexes from Cellular Lysates
1Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 2Centre for Biological Signalling Studies (bioss) and Biology III, Faculty of Biology, University of Freiburg, 3Department of Molecular Immunology, Max-Planck-Institute of Immunology and Epigenetics
In this video, we describe the characterization of multiprotein complexes (MPCs) by blue native polyacrylamide gel electrophoresis (BN-PAGE). In a first dimension, dialyzed cellular lysates are separated by BN-PAGE to identify individual MPCs. In a second dimension SDS-PAGE, MPCs of interest are further subdivided to analyze their constituents by immunoblotting.
JoVE General
Selective Labelling of Cell-surface Proteins using CyDye DIGE Fluor Minimal Dyes
Research and Development, GE Healthcare Bio-Sciences AB
A simple and specific method was demonstrated for fluorescent labeling and enhanced detection of cell surface proteins without a fractionation step. Differential abundance in cell surface proteins was analyzed using two-dimensional (2-D) electrophoresis and Ettan™ DIGE technology.
JoVE General
Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
1Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, 2Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, 3Department of Anesthesiology, Medicine and Physiology, David Geffen School of Medicine, University of California, Los Angeles
We describe a simple protocol to identify brain proteins that bind to the full length C terminus of ATP-gated P2X2 receptors. The extension and systematic application of this approach to all P2X receptors is expected to lead to a better understanding of P2X receptor signaling.
JoVE General
A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation
1Max Planck Institute of Molecular Plant Physiology, 2University of Kaiserslautern
We present a variation of the QUICK (QUantitative Immunoprecipitation Combined with Knockdown) approach that was introduced previously to distinguish between true and false protein-protein interactions. Our approach is based on 15N metabolic labeling, the modulation of affinities of protein-protein interactions by the presence/absence of ATP, immunoprecipitation, and quantitative mass spectrometry.
JoVE General
Visualizing Single Molecular Complexes In Vivo Using Advanced Fluorescence Microscopy
1Biochemistry, University of Oxford, 2Physics, University of Oxford
Here we demonstrate the protocols for performing single-molecule fluorescence microscopy on living bacterial cells to enable functional molecular complexes to be detected, tracked and quantified.
JoVE Immunology and Infection
Structure of HIV-1 Capsid Assemblies by Cryo-electron Microscopy and Iterative Helical Real-space Reconstruction
Department of Structural Biology, University of Pittsburgh School of Medicine
This article describes a method to obtain a three-dimensional (3D) structure of helically assembled molecules using cryo-electron microscopy. In this protocol, we use HIV-1 capsid assemblies to illustrate the detailed 3D reconstruction procedure for achieving a density map by the iterative helical real-space reconstruction method.
JoVE Neuroscience
Imaging pHluorin-tagged Receptor Insertion to the Plasma Membrane in Primary Cultured Mouse Neurons
By tagging the extracellular domains of membrane receptors with superecliptic pHluorin, and by imaging these fusion receptors in cultured mouse neurons, we can directly visualize individual vesicular insertion events of the receptors to the plasma membrane. This technique will be instrumental in elucidating the molecular mechanisms governing receptor insertion to the plasma membrane.
JoVE General
Photobleaching Assays (FRAP & FLIP) to Measure Chromatin Protein Dynamics in Living Embryonic Stem Cells
We describe photobleaching methods including Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Loss In Photobleaching (FLIP) to monitor chromatin protein dynamics in embryonic stem (ES) cells. Chromatin protein dynamics, which is considered to be one of the means to study chromatin plasticity, is enhanced in pluripotent cells.
JoVE Neuroscience
Fluorescence Recovery After Photobleaching (FRAP) of Fluorescence Tagged Proteins in Dendritic Spines of Cultured Hippocampal Neurons
FRAP has been used to quantify the mobility of Green Fluorescence Protein (GFP)-tagged proteins in cultured cells. We examined the mobile/immobile fractions of the GFP by analyzing the fluorescence recovery percentage after photobleaching. In this study, FRAP was performed at spines of hippocampal neurons.
JoVE General
Expression and Purification of the Cystic Fibrosis Transmembrane Conductance Regulator Protein in Saccharomyces cerevisiae
Faculty of Life Sciences, University of Manchester
Attempts to express the cystic fibrosis transmembrane conductance regulator (CFTR) in Saccharomyces cerevisiae have, until now, yielded relatively low amounts of protein. This protocol and the associated reagents distributed via the Cystic Fibrosis Foundation should allow the preparation of milligram amounts of this 'difficult' eukaryotic membrane protein.
JoVE General
Genetic Modification and Recombination of Salivary Gland Organ Cultures
Department of Biological Sciences, University at Albany, SUNY
A technique to genetically manipulate epithelial cells within whole ex vivo cultured embryonic mouse submandibular glands (SMGs) using viral gene transfer is described. This method takes advantage of the innate ability of SMG epithelium and mesenchyme to spontaneously recombine after separation and infection of epithelial rudiments with adenoviral vectors.
JoVE General
Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells
Department of Biochemistry, University of Toronto
Here we describe a method to visualize endoplasmic reticulum-associated mRNAs in mammalian tissue culture cells. This technique involves the selective permeabilization of the plasma membrane with digitonin to remove cytoplasmic contents followed by fluorescent in situ hybridization to detect either bulk poly(A) mRNA or specific transcripts.
JoVE General
In-vivo Detection of Protein-protein Interactions on Micro-patterned Surfaces
Institute of Biophysics, Johannes Kepler Universitat Linz
This video shows experiments with subsequent analysis of protein-protein interactions by the use of micro-patterned surfaces. The approach offers the possibility to detect protein interactions in living cells and combines high throughput capabilities with the possibility to extract quantitative information.
JoVE Neuroscience
F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes
Department of Internal Medicine, Yale University
A method to isolate submitochondrial vesicles enriched in F1FO ATP synthase complexes from rat brain is described. These vesicles allow the study of the activity of F1FO ATPase complex and its modulation using the technique of patch clamp recording.
JoVE General
Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms
1Medical Biochemistry and Molecular Biology, Saarland University, 2Experimental and Clinical Pharmacology and Toxicology, Saarland University
The endoplasmic reticulum plays a key role in protein biogenesis and in calcium homeostasis. We have established an experimental system that allows us to address the role of Ca2+ leak channels and to characterize their putative regulatory mechanisms. This system involves siRNA mediated gene silencing and live cell Ca2+ imaging.
JoVE Immunology and Infection
Development of Cell-type specific anti-HIV gp120 aptamers for siRNA delivery
1Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope, 2Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, 3Shared Resource-DNA/RNA Peptide, Beckman Research Institute of City of Hope
Several 2’-Fluoro RNA aptamers against HIV-1Ba-L gp120 with nanomole affinity are isolated from a RNA library by in vitro SELEX procedure. A new dual inhibitory function anti-gp120 aptamer-siRNA chimera is created and shows considerable promise for systemic anti-HIV therapy.
JoVE Neuroscience
Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae
Epigenetics and Progenitor Cells Keystone, Fox Chase Cancer Center
In this video, we describe a method for live cell imaging of asymmetrically dividing sensory organ progenitor cells and epidermal cells in intact Drosophila pupae
JoVE General
Measuring Cation Transport by Na,K- and H,K-ATPase in Xenopus Oocytes by Atomic Absorption Spectrophotometry: An Alternative to Radioisotope Assays
1Institute of Chemistry, Technical University of Berlin, 2The Vollum Institute, Oregon Health & Science University
We describe a method to quantify the activity of K+-countertransporting P-type ATPases by heterologous expression of the enzymes in Xenopus oocytes and measuring Rb+ or Li+ uptake into individual cells by atomic absorption spectrophotometry. The method is a sensitive and safe alternative to radioisotope flux experiments facilitating complex kinetic studies.
JoVE Bioengineering
Constant Pressure-controlled Extrusion Method for the Preparation of Nano-sized Lipid Vesicles
1Department of Chemistry & Biochemistry, University of Colorado Boulder, 2Biofrontiers Institute, University of Colorado Boulder
This protocol describes an extrusion method for preparing lipid vesicles of sub-micron sizes with a high degree of homogeneity. This method uses a pressure-controlled system with controlled nitrogen flow rates for liposome preparation. The lipid preparation1,2, liposome extrusion, and size characterization will be presented herein.
JoVE General
Isolation and In vitro Activation of Caenorhabditis elegans Sperm
Waksman Institute of Microbiology, Rutgers University
A protocol for isolating and activating spermatids from male C. elegans is described here. Cutting the posterior end of male releases spermatids. The spermatids can be activated by addition of protease.
JoVE Bioengineering
Visualization of Cortex Organization and Dynamics in Microorganisms, using Total Internal Reflection Fluorescence Microscopy
1AG Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, 2Helmholtz Zentrum München
Total Internal Reflection Fluorescence (TIRF) microscopy is a powerful approach to observe structures close to the cell surface at high contrast and temporal resolution. We demonstrate how TIRF can be employed to study protein dynamics at the cortex of cell wall-enclosed bacterial and fungal cells.
JoVE General
Avidity-based Extracellular Interaction Screening (AVEXIS) for the Scalable Detection of Low-affinity Extracellular Receptor-Ligand Interactions
Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute
AVEXIS is a high throughput protein interaction assay developed to systematically screen for novel extracellular receptor-ligand pairs involved in cellular recognition processes. It is specifically designed to detect transient protein interactions that are difficult to identify using other high throughput approaches.
JoVE General
Identification and Analysis of Mouse Erythroid Progenitors using the CD71/TER119 Flow-cytometric Assay
A flow-cytometric method for identification and molecular analysis of differentiation-stage-specific murine erythroid progenitors and precursors, directly in freshly –harvested mouse bone marrow, spleen or fetal liver. The assay relies on cell-surface markers CD71, Ter119, and cell size.
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