scholarly journals Lipids modulate the insertion and folding of the nascent chains of alpha helical membrane proteins

2018 ◽  
Vol 46 (5) ◽  
pp. 1355-1366 ◽  
Author(s):  
Nicola J. Harris ◽  
Kalypso Charalambous ◽  
Heather E. Findlay ◽  
Paula J. Booth
Keyword(s):  
Membrane Proteins ◽  
Lipid Composition ◽  
Oligomeric Proteins ◽  
Recent Advances ◽  
Lipid Environment ◽  
Correct Structure

Membrane proteins must be inserted into a membrane and folded into their correct structure to function correctly. This insertion occurs during translation and synthesis by the ribosome for most α-helical membrane proteins. Precisely how this co-translational insertion and folding occurs, and the role played by the surrounding lipids, is still not understood. Most of the work on the influence of the lipid environment on folding and insertion has focussed on denatured, fully translated proteins, and thus does not replicate folding during unidirectional elongation of nascent chains that occurs in the cell. This review aims to highlight recent advances in elucidating lipid composition and bilayer properties optimal for insertion and folding of nascent chains in the membrane and in the assembly of oligomeric proteins.

scholarly journals Structural predictions of the functions of membrane proteins from HDX-MS

2020 ◽  
Vol 48 (3) ◽  
pp. 971-979
Author(s):  
Andy M. Lau ◽  
Ruyu Jia ◽  
Richard T. Bradshaw ◽  
Argyris Politis
Keyword(s):  
Experimental Data ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Short Review ◽  
Fundamental Knowledge ◽  
Significant Potential ◽  
Structure And Dynamics ◽  
Recent Advances ◽  
Lipid Environment ◽  
Hdx Ms

HDX-MS has emerged as a powerful tool to interrogate the structure and dynamics of proteins and their complexes. Recent advances in the methodology and instrumentation have enabled the application of HDX-MS to membrane proteins. Such targets are challenging to investigate with conventional strategies. Developing new tools are therefore pertinent for improving our fundamental knowledge of how membrane proteins function in the cell. Importantly, investigating this central class of biomolecules within their native lipid environment remains a challenge but also a key goal ahead. In this short review, we outline recent progresses in dissecting the conformational mechanisms of membrane proteins using HDX-MS. We further describe how the use of computational strategies can aid the interpretation of experimental data and enable visualisation of otherwise intractable membrane protein states. This unique integration of experiments with computations holds significant potential for future applications.

scholarly journals Co-Translational Insertion of Aquaporins into Liposome for Functional Analysis via an E. coli Based Cell-Free Protein Synthesis System

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1325 ◽  
Author(s):  
Ke Yue ◽  
Tran Nam Trung ◽  
Yiyong Zhu ◽  
Ralf Kaldenhoff ◽  
Lei Kai
Keyword(s):  
Functional Analysis ◽  
Membrane Proteins ◽  
Fluorescent Protein ◽  
Water Channel ◽  
New Approach ◽  
E Coli ◽  
Straightforward Method ◽  
Lipid Environment ◽  
Green Fluorescent ◽  
Eukaryotic Organisms

Aquaporins are important and well-studied water channel membrane proteins. However, being membrane proteins, sample preparation for functional analysis is tedious and time-consuming. In this paper, we report a new approach for the co-translational insertion of two aquaporins from Escherichia coli and Nicotiana tabacum using the CFPS system. This was done in the presence of liposomes with a modified procedure to form homogenous proteo-liposomes suitable for functional analysis of water permeability using stopped-flow spectrophotometry. Two model aquaporins, AqpZ and NtPIP2;1, were successfully incorporated into the liposome in their active forms. Shifted green fluorescent protein was fused to the C-terminal part of AqpZ to monitor its insertion and status in the lipid environment. This new fast approach offers a fast and straightforward method for the functional analysis of aquaporins in both prokaryotic and eukaryotic organisms.

scholarly journals Lipid Transporters Beam Signals from Cell Membranes

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 562
Author(s):  
Miliça Ristovski ◽  
Danny Farhat ◽  
Shelly Ellaine M. Bancud ◽  
Jyh-Yeuan Lee
Keyword(s):  
Membrane Proteins ◽  
Lipid Bilayers ◽  
Lipid Composition ◽  
Structural Integrity ◽  
Current Knowledge ◽  
Integral Membrane Proteins ◽  
Cellular Membranes ◽  
Cytoplasmic Proteins ◽  
Lipid Transporters

Lipid composition in cellular membranes plays an important role in maintaining the structural integrity of cells and in regulating cellular signaling that controls functions of both membrane-anchored and cytoplasmic proteins. ATP-dependent ABC and P4-ATPase lipid transporters, two integral membrane proteins, are known to contribute to lipid translocation across the lipid bilayers on the cellular membranes. In this review, we will highlight current knowledge about the role of cholesterol and phospholipids of cellular membranes in regulating cell signaling and how lipid transporters participate this process.

scholarly journals Lipid Bilayer Composition Affects Transmembrane Protein Orientation and Function

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Katie D. Hickey ◽  
Mary M. Buhr
Keyword(s):  
Lipid Bilayer ◽  
Lipid Composition ◽  
Protein Function ◽  
Transmembrane Protein ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Outer Leaflet ◽  
Lipid Environment ◽  
Protein Incorporation ◽  
And Function

Sperm membranes change in structure and composition upon ejaculation to undergo capacitation, a molecular transformation which enables spermatozoa to undergo the acrosome reaction and be capable of fertilization. Changes to the membrane environment including lipid composition, specifically lipid microdomains, may be responsible for enabling capacitation. To study the effect of lipid environment on proteins, liposomes were created using lipids extracted from bull sperm membranes, with or without a protein (Na+K+-ATPase or -amylase). Protein incorporation, function, and orientation were determined. Fluorescence resonance energy transfer (FRET) confirmed protein inclusion in the lipid bilayer, and protein function was confirmed using a colourometric assay of phosphate production from ATP cleavage. In the native lipid liposomes, ATPase was oriented with the subunit facing the outer leaflet, while changing the lipid composition to 50% native lipids and 50% exogenous lipids significantly altered this orientation of Na+K+-ATPase within the membranes.

scholarly journals Lipid-protein interactions are unique fingerprints for membrane proteins

2017 ◽  
Author(s):  
Valentina Corradi ◽  
Eduardo Mendez-Villuendas ◽  
Helgi I. Ingólfsson ◽  
Ruo-Xu Gu ◽  
Iwona Siuda ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Interactions ◽  
Cell Membranes ◽  
Spatiotemporal Resolution ◽  
Lipid Dynamics ◽  
Lipid Species ◽  
Lipid Environment ◽  
Lipid Protein Interactions ◽  
Dynamics Simulations ◽  
Asymmetrically Distributed

ABSTRACTCell membranes contain hundreds of different proteins and lipids in an asymmetric arrangement. Understanding the lateral organization principles of these complex mixtures is essential for life and health. However, our current understanding of the detailed organization of cell membranes remains rather elusive, owing to the lack of experimental methods suitable for studying these fluctuating nanoscale assemblies of lipids and proteins with the required spatiotemporal resolution. Here, we use molecular dynamics simulations to characterize the lipid environment of ten membrane proteins. To provide a realistic lipid environment, the proteins are embedded in a model plasma membrane, where more than 60 lipid species are represented, asymmetrically distributed between leaflets. The simulations detail how each protein modulates its local lipid environment through local lipid composition, thickness, curvature and lipid dynamics. Our results provide a molecular glimpse of the complexity of lipid-protein interactions, with potentially far reaching implications for the overall organization of the cell membrane.

Circular Dichroism Analysis of Native and Reaggregated Mycoplasma Membranes

1973 ◽  
Vol 51 (5) ◽  
pp. 632-636 ◽  
Author(s):  
Shlomo Rottem ◽  
Leonard Hayflick
Keyword(s):  
Circular Dichroism ◽  
Membrane Proteins ◽  
Sodium Dodecyl Sulfate ◽  
Lipid Composition ◽  
Sodium Dodecyl ◽  
Growth Cycle ◽  
Membrane Material ◽  
Α Helix ◽  
Low Amplitude ◽  
Circular Dichroïsm

Circular dichroism analyses of Acholeplasma laidlawii membranes solubilized by sodium dodecyl sulfate showed a typical α-helix spectrum. The estimated α-helix content was of the order of 35% calculated from the ellipticity at 208 nm of membranes solubilized by 20 mM SDS. Reaggregation of the solubilized membrane material to a membrane-like structure resulted in a distorted spectrum with low amplitude and red-shifted extrema like that of the native membranes. Throughout the growth cycle the circular dichroism spectra of membrane proteins remained the same despite the marked differences in membrane densities. The optical activity of the membranes was not affected by changing the lipid composition or extraction of over 90% of the lipids, although the latter resulted in marked destabilization of the proteins.

scholarly journals Stability and flexibility of marginally hydrophobic–segment stalling at the endoplasmic reticulum translocon

2016 ◽  
Vol 27 (6) ◽  
pp. 930-940 ◽  
Author(s):  
Yuichiro Kida ◽  
Yudai Ishihara ◽  
Hidenobu Fujita ◽  
Yukiko Onishi ◽  
Masao Sakaguchi
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Lipid Phase ◽  
Endoplasmic Reticulum Membrane ◽  
Dependent Manner ◽  
Transmembrane Segment ◽  
Conducting Channel ◽  
Transmembrane Segments ◽  
Lipid Environment ◽  
Sec61 Channel

Many membrane proteins are integrated into the endoplasmic reticulum membrane through the protein-conducting channel, the translocon. Transmembrane segments with insufficient hydrophobicity for membrane integration are frequently found in multispanning membrane proteins, and such marginally hydrophobic (mH) segments should be accommodated, at least transiently, at the membrane. Here we investigated how mH-segments stall at the membrane and their stability. Our findings show that mH-segments can be retained at the membrane without moving into the lipid phase and that such segments flank Sec61α, the core channel of the translocon, in the translational intermediate state. The mH-segments are gradually transferred from the Sec61 channel to the lipid environment in a hydrophobicity-dependent manner, and this lateral movement may be affected by the ribosome. In addition, stalling mH-segments allow for insertion of the following transmembrane segment, forming an Ncytosol/Clumen orientation, suggesting that mH-segments can move laterally to accommodate the next transmembrane segment. These findings suggest that mH-segments may be accommodated at the ER membrane with lateral fluctuation between the Sec61 channel and the lipid phase.

scholarly journals Structure and Dynamics of Nanopore-Confined Membrane Proteins are Affected by Bilayer Lipid Composition

2017 ◽  
Vol 112 (3) ◽  
pp. 388a
Author(s):  
Alexander A. Nevzorov ◽  
Morteza Jafarabadi ◽  
Antonin Marek ◽  
Alex I. Smirnov
Keyword(s):  
Membrane Proteins ◽  
Lipid Composition ◽  
Bilayer Lipid ◽  
Structure And Dynamics

Cryo-Electron Microscopy: Moving Beyond X-Ray Crystal Structures for Drug Receptors and Drug Development

2020 ◽  
Vol 60 (1) ◽  
pp. 51-71 ◽  
Author(s):  
Javier García-Nafría ◽  
Christopher G. Tate
Keyword(s):  
Membrane Proteins ◽  
G Protein ◽  
Rational Design ◽  
Protein Complexes ◽  
Host Cells ◽  
X Ray ◽  
X Ray Crystallography ◽  
Receptor Modulation ◽  
Lipid Environment ◽  
Drug Receptors

Electron cryo-microscopy (cryo-EM) has revolutionized structure determination of membrane proteins and holds great potential for structure-based drug discovery. Here we discuss the potential of cryo-EM in the rational design of therapeutics for membrane proteins compared to X-ray crystallography. We also detail recent progress in the field of drug receptors, focusing on cryo-EM of two protein families with established therapeutic value, the γ-aminobutyric acid A receptors (GABAARs) and G protein–coupled receptors (GPCRs). GABAARs are pentameric ion channels, and cryo-EM structures of physiological heteromeric receptors in a lipid environment have uncovered the molecular basis of receptor modulation by drugs such as diazepam. The structures of ten GPCR–G protein complexes from three different classes of GPCRs have now been determined by cryo-EM. These structures give detailed insights into molecular interactions with drugs, GPCR–G protein selectivity, how accessory membrane proteins alter receptor–ligand pharmacology, and the mechanism by which HIV uses GPCRs to enter host cells.

Sign in / Sign up

Export Citation Format

Share Document