scholarly journals Membrane Lipids and the Conformations of Membrane Proteins

1969 ◽  
Vol 54 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Donald F. H. Wallach
Keyword(s):  
Membrane Proteins ◽  
Protein Interactions ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Sodium Dodecyl ◽  
Ehrlich Ascites Carcinoma ◽  
Optical Rotatory Dispersion ◽  
Protein Protein Interactions ◽  
Ehrlich Ascites ◽  
General Relations

The general relations between protein conformation and the optical activity of peptide chromophores are outlined and applied to the analysis of the optical rotatory dispersion and circular dichroism of the plasma membranes of human erythrocytes and Ehrlich ascites carcinoma cells. It is concluded that the proteins of these membranes are "globular" and that they have considerable helical content. The spectroscopic consequences of perturbing the membranes with phospholipase C, phospholipase A, lysolecithin, and sodium dodecyl sulfate are examined in the light of the effects of these agents upon certain enzymatic and physical properties of the membranes and upon their proton magnetic resonance spectra. The data suggest that the architecture of membrane proteins is strongly dependent upon apolar lipid-protein and/or lipid-sensitive protein-protein interactions.

scholarly journals Insights into the Role of Membrane Lipids in the Structure, Function and Regulation of Integral Membrane Proteins

2021 ◽  
Vol 22 (16) ◽  
pp. 9026
Author(s):  
Kenta Renard ◽  
Bernadette Byrne
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Conformational Changes ◽  
Protein Interactions ◽  
Membrane Lipids ◽  
Protein Protein Interactions ◽  
Technological Advances ◽  
Highly Hydrophobic ◽  
Dynamics Simulations ◽  
And Function

Membrane proteins exist within the highly hydrophobic membranes surrounding cells and organelles, playing key roles in cellular function. It is becoming increasingly clear that the membrane does not just act as an appropriate environment for these proteins, but that the lipids that make up these membranes are essential for membrane protein structure and function. Recent technological advances in cryogenic electron microscopy and in advanced mass spectrometry methods, as well as the development of alternative membrane mimetic systems, have allowed experimental study of membrane protein–lipid complexes. These have been complemented by computational approaches, exploiting the ability of Molecular Dynamics simulations to allow exploration of membrane protein conformational changes in membranes with a defined lipid content. These studies have revealed the importance of lipids in stabilising the oligomeric forms of membrane proteins, mediating protein–protein interactions, maintaining a specific conformational state of a membrane protein and activity. Here we review some of the key recent advances in the field of membrane protein–lipid studies, with major emphasis on respiratory complexes, transporters, channels and G-protein coupled receptors.

Transmembrane phospholipid distribution revealed by freeze-fracture replica labeling

1996 ◽  
Vol 109 (10) ◽  
pp. 2453-2460 ◽  
Author(s):  
K. Fujimoto ◽  
M. Umeda ◽  
T. Fujimoto
Keyword(s):  
Plasma Membranes ◽  
Membrane Lipids ◽  
Secretory Granules ◽  
General Scheme ◽  
Sodium Dodecyl ◽  
Freeze Fracture ◽  
Electron Microscopic Observation ◽  
Erythrocyte Membranes ◽  
Electron Microscopic ◽  
Intracellular Membranes

We propose the use of membrane splitting by freeze-fracture for differential phospholipid analysis of protoplasmic and exoplasmic membrane leaflets (halves). Unfixed cells or tissues are quick-frozen, freeze-fractured, and platinum-carbon (Pt/C) shadowed. The Pt/C replicas are then treated with 2.5% sodium dodecyl sulfate (SDS) to solubilize unfractured membranes and to release cytoplasm or contents. While the detergent dissolves unfractured membranes, it would not extract lipids from split membranes, as their apolar domains are stabilized by their Pt/C replicas. After washing, the Pt/C replicas, along with attached protoplasmic and exoplasmic membrane halves, are processed for immunocytochemical labeling of phospholipids with antibody, followed by electron microscopic observation. Here, we present the application of the SDS-digested freeze-fracture replica labeling (SDS-FRL) technique to the transmembrane distribution of a major membrane phospholipid, phosphatidylcholine (PC), in various cell and intracellular membranes. Immunogold labeling revealed that PC is exclusively localized on the exoplasmic membrane halves of the plasma membranes, and the intracellular membranes of various organelles, e.g. nuclei, mitochondria, endoplasmic reticulum, secretory granules, and disc membranes of photoreceptor cells. One exception to this general scheme was the plasma membrane forming the myelin sheath of neurons and the Ca(2+)-treated erythrocyte membranes. In these cell membranes, roughly equal amounts of immunogold particles for PC were seen on each outer and inner membrane half, implying a symmetrical transmembrane distribution of PC. Initial screening suggests that the SDS-FRL technique allows in situ analysis of the transmembrane distribution of membrane lipids, and at the same time opens up the possibility of labeling membranes such as intracellular membranes not normally accessible to cytochemical labels without the distortion potentially associated with membrane isolation procedures.

scholarly journals Divisome under Construction: Distinct Domains of the Small Membrane Protein FtsB Are Necessary for Interaction with Multiple Cell Division Proteins

2009 ◽  
Vol 191 (8) ◽  
pp. 2815-2825 ◽  
Author(s):  
Mark D. Gonzalez ◽  
Jon Beckwith
Keyword(s):  
Cell Division ◽  
Membrane Proteins ◽  
Protein Interactions ◽  
Cell Envelope ◽  
Coiled Coil ◽  
Main Function ◽  
Protein Protein Interactions ◽  
Molecular Scaffold ◽  
C Terminus ◽  
Under Construction

ABSTRACT Cell division in bacteria requires the coordinated action of a set of proteins, the divisome, for proper constriction of the cell envelope. Multiple protein-protein interactions are required for assembly of a stable divisome. Within the Escherichia coli divisome is a conserved subcomplex of inner membrane proteins, the FtsB/FtsL/FtsQ complex, which is necessary for linking the upstream division proteins, which are predominantly cytoplasmic, with the downstream division proteins, which are predominantly periplasmic. FtsB and FtsL are small bitopic membrane proteins with predicted coiled-coil motifs, which themselves form a stable subcomplex that can recruit downstream division proteins independently of FtsQ; however, the details of how FtsB and FtsL interact together and with other proteins remain to be characterized. Despite the small size of FtsB, we identified separate interaction domains of FtsB that are required for interaction with FtsL and FtsQ. The N-terminal half of FtsB is necessary for interaction with FtsL and sufficient, when in complex with FtsL, for recruitment of downstream division proteins, while a portion of the FtsB C terminus is necessary for interaction with FtsQ. These properties of FtsB support the proposal that its main function is as part of a molecular scaffold to allow for proper formation of the divisome.

Myogenesis of normal and dystrophic chick embryonic skeletal muscle cells in vitro: biosynthesis of plasma membrane proteins

1980 ◽  
Vol 58 (10) ◽  
pp. 1156-1164 ◽  
Author(s):  
Paul C. Holland ◽  
George A. Cates ◽  
Byron S. Wenger ◽  
Barbara L. Raney
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Plasma Membranes ◽  
Protein Biosynthesis ◽  
Sodium Dodecyl ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Plasma Membrane Proteins ◽  
Dystrophic Muscle

Plasma membranes were prepared from primary cell cultures of normal and genetically dystrophic chick embryonic pectoral muscle. These membranes were analyzed both by one-dimensional sodium dodecyl sulphate – polyacrylamide slab gel electrophoresis and by two-dimensional electrophoresis using isoelectric focusing in the first dimension. No marked and reproducible abnormalities could be detected in the synthesis, or accumulation, of plasma membrane proteins of dystrophic muscle cells maintained in culture for periods of up to 6 days. Analysis of the relative rates of protein turnover, analysis of fucose incorporation into plasma membrane proteins, and comparison of iodinated cell surface proteins also failed to reveal distinct abnormalities in plasma membranes derived from cultured dystrophic muscle cells. Although the results obtained do not rule out an early defect in plasma membrane protein biosynthesis during the development of dystrophic skeletal muscle in vivo, they do demonstrate that the synthesis and assembly of at least the major plasma membrane proteins occur normally during the initial phases of terminal differentiation of isolated dystrophic skeletal muscle cells in tissue culture.

scholarly journals Domains of alpha-SNAP required for the stimulation of exocytosis and for N-ethylmalemide-sensitive fusion protein (NSF) binding and activation.

1996 ◽  
Vol 7 (5) ◽  
pp. 693-701 ◽  
Author(s):  
R J Barnard ◽  
A Morgan ◽  
R D Burgoyne
Keyword(s):  
Membrane Proteins ◽  
Fusion Protein ◽  
Conformational Changes ◽  
Protein Interactions ◽  
Atp Hydrolysis ◽  
Coiled Coil ◽  
Protein Protein Interactions ◽  
Permeabilized Cells ◽  
C Terminus ◽  
Adrenal Chromaffin

The binding of alpha-SNAP to the membrane proteins syntaxin, SNAP-25, and synaptobrevin leads to the recruitment of the N-ethylmaleimide-sensitive fusion protein (NSF). ATP hydrolysis by NSF has been suggested to drive conformational changes in one or more of these membrane proteins that are essential for regulated exocytosis. Functional evidence for a role of alpha-SNAP in exocytosis in adrenal chromaffin cells comes from the ability of this protein to stimulate Ca(2+)-dependent exocytosis in digitonin-permeabilized cells. Here we examine the effect of a series of deletion mutants of alpha-SNAP on exocytosis, and on the ability of alpha-SNAP to interact with NSF, to define essential domains involved in protein-protein interactions in exocytosis. Deletion of extreme N- or C-terminal regions of alpha-SNAP produced proteins unable to bind to syntaxin or to stimulate exocytosis, suggesting that these domains participate in essential interactions. Deletion of C-terminal residues abolished the ability of alpha-SNAP to bind NSF. In contrast, deletion of up to 120 N-terminal residues did not prevent the binding of NSF to immobilized alpha-SNAP and such mutants were also able to stimulate the ATPase activity of NSF. These results suggest that the C-terminus, but not the N-terminus, of alpha-SNAP is crucial for interactions with NSF. The involvement of the C-terminus of alpha-SNAP, which contains a predicted coiled-coil domain, in the binding of both syntaxin and NSF would place the latter two proteins in proximity in a ternary complex whereupon the energy derived from ATP hydrolysis by NSF could induce a conformational change in syntaxin required for exocytosis to proceed.

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