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Biochimica Et Biophysica Acta Nov 2004Phospholipids are essential building blocks of membranes and maintain the membrane permeability barrier of cells and organelles. They provide not only the bilayer matrix... (Review)
Review
Phospholipids are essential building blocks of membranes and maintain the membrane permeability barrier of cells and organelles. They provide not only the bilayer matrix in which the functional membrane proteins reside, but they also can play direct roles in many essential cellular processes. In this review, we give an overview of the lipid involvement in protein translocation across and insertion into the Escherichia coli inner membrane. We describe the key and general roles that lipids play in these processes in conjunction with the protein components involved. We focus on the Sec-mediated insertion of leader peptidase. We describe as well the more direct roles that lipids play in insertion of the small coat proteins Pf3 and M13. Finally, we focus on the role of lipids in membrane assembly of oligomeric membrane proteins, using the potassium channel KcsA as model protein. In all cases, the anionic lipids and lipids with small headgroups play important roles in either determining the efficiency of the insertion and assembly process or contributing to the directionality of the insertion process.
Topics: Cell Membrane; Escherichia coli Proteins; Membrane Lipids; Membrane Proteins; Protein Transport
PubMed: 15546660
DOI: 10.1016/j.bbamcr.2004.03.007 -
Journal of Plant Research Jul 2016The lipid bilayer of the thylakoid membrane in plant chloroplasts and cyanobacterial cells is predominantly composed of four unique lipid classes;... (Review)
Review
The lipid bilayer of the thylakoid membrane in plant chloroplasts and cyanobacterial cells is predominantly composed of four unique lipid classes; monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG). MGDG and DGDG are uncharged galactolipids that constitute the bulk of thylakoid membrane lipids and provide a lipid bilayer matrix for photosynthetic complexes as the main constituents. The glycolipid SQDG and phospholipid PG are anionic lipids with a negative charge on their head groups. SQDG and PG substitute for each other to maintain the amount of total anionic lipids in the thylakoid membrane, with PG having indispensable functions in photosynthesis. In addition to biochemical studies, extensive analyses of mutants deficient in thylakoid lipids have revealed important roles of these lipids in photosynthesis and thylakoid membrane biogenesis. Moreover, recent studies of Arabidopsis thaliana suggest that thylakoid lipid biosynthesis triggers the expression of photosynthesis-associated genes in both the nucleus and plastids and activates the formation of photosynthetic machineries and chloroplast development. Meanwhile, galactolipid biosynthesis is regulated in response to chloroplast functionality and lipid metabolism at transcriptional and post-translational levels. This review summarizes the roles of thylakoid lipids with their biosynthetic pathways in plants and discusses the coordinated regulation of thylakoid lipid biosynthesis with the development of photosynthetic machinery during chloroplast biogenesis.
Topics: Membrane Lipids; Organelle Biogenesis; Photosynthesis; Plant Cells; Plant Leaves; Thylakoids
PubMed: 27114097
DOI: 10.1007/s10265-016-0827-y -
Biochimica Et Biophysica Acta Sep 2015We review the importance of helix motions for the function of several important categories of membrane proteins and for the properties of several model molecular... (Review)
Review
We review the importance of helix motions for the function of several important categories of membrane proteins and for the properties of several model molecular systems. For voltage-gated potassium or sodium channels, sliding, tilting and/or rotational movements of the S4 helix accompanied by a swapping of cognate side-chain ion-pair interactions regulate the channel gating. In the seven-helix G protein-coupled receptors, exemplified by the rhodopsins, collective helix motions serve to activate the functional signaling. Peptides which initially associate with lipid-bilayer membrane surfaces may undergo dynamic transitions from surface-bound to tilted-transmembrane orientations, sometimes accompanied by changes in the molecularity, formation of a pore or, more generally, the activation of biological function. For single-span membrane proteins, such as the tyrosine kinases, an interplay between juxtamembrane and transmembrane domains is likely to be crucial for the regulation of dimer assembly that in turn is associated with the functional responses to external signals. Additionally, we note that experiments with designed single-span transmembrane helices offer fundamental insights into the molecular features that govern protein-lipid interactions. This article is part of a Special Issue entitled: Lipid-protein interactions.
Topics: Animals; Humans; Kinetics; Lipid Bilayers; Membrane Lipids; Membrane Proteins; Models, Molecular; Protein Binding; Protein Structure, Secondary; Protein Structure, Tertiary
PubMed: 25666872
DOI: 10.1016/j.bbamem.2015.01.019 -
International Journal of Molecular... Aug 2021Membrane proteins exist within the highly hydrophobic membranes surrounding cells and organelles, playing key roles in cellular function. It is becoming increasingly... (Review)
Review
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.
Topics: Animals; Membrane Lipids; Membrane Proteins
PubMed: 34445730
DOI: 10.3390/ijms22169026 -
Cold Spring Harbor Perspectives in... Oct 2011Viruses intricately interact with and modulate cellular membranes at several stages of their replication, but much less is known about the role of viral lipids compared... (Review)
Review
Viruses intricately interact with and modulate cellular membranes at several stages of their replication, but much less is known about the role of viral lipids compared to proteins and nucleic acids. All animal viruses have to cross membranes for cell entry and exit, which occurs by membrane fusion (in enveloped viruses), by transient local disruption of membrane integrity, or by cell lysis. Furthermore, many viruses interact with cellular membrane compartments during their replication and often induce cytoplasmic membrane structures, in which genome replication and assembly occurs. Recent studies revealed details of membrane interaction, membrane bending, fission, and fusion for a number of viruses and unraveled the lipid composition of raft-dependent and -independent viruses. Alterations of membrane lipid composition can block viral release and entry, and certain lipids act as fusion inhibitors, suggesting a potential as antiviral drugs. Here, we review viral interactions with cellular membranes important for virus entry, cytoplasmic genome replication, and virus egress.
Topics: Genome, Viral; Membrane Lipids; Membrane Microdomains; Models, Biological; Transport Vesicles; Virus Internalization; Virus Replication
PubMed: 21628428
DOI: 10.1101/cshperspect.a004820 -
Biochimica Et Biophysica Acta Nov 2004This review is focused on peptide molecules which exhibit a limited solubility in the aqueous phase and bind to the lipid membrane from the aqueous medium. Surface... (Review)
Review
This review is focused on peptide molecules which exhibit a limited solubility in the aqueous phase and bind to the lipid membrane from the aqueous medium. Surface adsorption, membrane insertion, and specific binding are usually accompanied by changes in the heat content of the system and can be measured conveniently with isothermal titration calorimetry, avoiding the necessity of peptide labeling. The driving forces for peptide adsorption and binding are hydrophobicity, electrostatics, and hydrogen bonding. An exclusively hydrophobic interaction is exemplified by the immunosuppressant drug cyclosporine A. Its insertion into the membrane can be described by a simple partition equilibrium X(b)=K(0)C(eq). If peptide and membrane are both charged, electrostatic interactions are dominant leading to nonlinear binding curves. The concentration of the peptide near the membrane interface can then be much larger than its bulk concentration. Electrostatic effects must be accounted for by means of the Gouy-Chapman theory before conventional binding models can be applied. A small number of peptides and proteins bind with very high affinity to a specific lipid species only. This is illustrated for the lantibiotic cinnamycin (Ro 09-0198) which forms a 1:1 complex with phosphatidyethanolamine with a binding constant of 10(8) M(-1). Membrane adsorption and insertion can be accompanied by conformational transitions facilitated, in part, by hydrogen bonding mechanisms. The two membrane-induced conformational changes to be discussed are the random coil-to-alpha-helix transition of amphipathic peptides and the random coil-to-beta-structure transition of Alzheimer peptides.
Topics: Membrane Lipids; Membrane Proteins; Peptides; Protein Binding; Protein Conformation; Thermodynamics
PubMed: 15519307
DOI: 10.1016/j.bbamem.2004.08.004 -
International Journal of Molecular... May 2021Sphingolipids are a specialized group of lipids essential to the composition of the plasma membrane of many cell types; however, they are primarily localized within the... (Review)
Review
Sphingolipids are a specialized group of lipids essential to the composition of the plasma membrane of many cell types; however, they are primarily localized within the nervous system. The amphipathic properties of sphingolipids enable their participation in a variety of intricate metabolic pathways. Sphingoid bases are the building blocks for all sphingolipid derivatives, comprising a complex class of lipids. The biosynthesis and catabolism of these lipids play an integral role in small- and large-scale body functions, including participation in membrane domains and signalling; cell proliferation, death, migration, and invasiveness; inflammation; and central nervous system development. Recently, sphingolipids have become the focus of several fields of research in the medical and biological sciences, as these bioactive lipids have been identified as potent signalling and messenger molecules. Sphingolipids are now being exploited as therapeutic targets for several pathologies. Here we present a comprehensive review of the structure and metabolism of sphingolipids and their many functional roles within the cell. In addition, we highlight the role of sphingolipids in several pathologies, including inflammatory disease, cystic fibrosis, cancer, Alzheimer's and Parkinson's disease, and lysosomal storage disorders.
Topics: Animals; Cell Membrane; Homeostasis; Humans; Inflammation; Membrane Lipids; Models, Chemical; Molecular Structure; Neoplasms; Sphingolipids
PubMed: 34071409
DOI: 10.3390/ijms22115793 -
Annual Review of Biochemistry 2009The topology of polytopic membrane proteins is determined by topogenic sequences in the protein, protein-translocon interactions, and interactions during folding within... (Review)
Review
The topology of polytopic membrane proteins is determined by topogenic sequences in the protein, protein-translocon interactions, and interactions during folding within the protein and between the protein and the lipid environment. Orientation of transmembrane domains is dependent on membrane phospholipid composition during initial assembly as well as on changes in lipid composition postassembly. The membrane translocation potential of negative amino acids working in opposition to the positive-inside rule is largely dampened by the normal presence of phosphatidylethanolamine, thus explaining the dominance of positive residues as retention signals. Phosphatidylethanolamine provides the appropriate charge density that permits the membrane surface to maintain a charge balance between membrane translocation and retention signals and also allows the presence of negative residues in the cytoplasmic face of proteins for other purposes.
Topics: Bacteria; Membrane Lipids; Membrane Proteins; Phosphatidylethanolamines; Protein Folding
PubMed: 19489728
DOI: 10.1146/annurev.biochem.77.060806.091251 -
Cold Spring Harbor Perspectives in... Sep 2011Ever since it was discovered that biological membranes have a core of a bimolecular sheet of lipid molecules, lipid bilayers have been a model laboratory for... (Review)
Review
Ever since it was discovered that biological membranes have a core of a bimolecular sheet of lipid molecules, lipid bilayers have been a model laboratory for investigating physicochemical and functional properties of biological membranes. Experimental and theoretical models help the experimental scientist to plan experiments and interpret data. Theoretical models are the theoretical scientist's preferred toys to make contact between membrane theory and experiments. Most importantly, models serve to shape our intuition about which membrane questions are the more fundamental and relevant ones to pursue. Here we review some membrane models for lipid self-assembly, monolayers, bilayers, liposomes, and lipid-protein interactions and illustrate how such models can help answering questions in modern lipid cell biology.
Topics: Liposomes; Membrane Lipids; Membrane Proteins; Models, Biological
PubMed: 21610116
DOI: 10.1101/cshperspect.a004622 -
Progress in Lipid Research Oct 2013Glycerophospholipids are the most abundant membrane lipid constituents in most eukaryotic cells. As a consequence, phospholipid class and acyl chain homeostasis are... (Review)
Review
Glycerophospholipids are the most abundant membrane lipid constituents in most eukaryotic cells. As a consequence, phospholipid class and acyl chain homeostasis are crucial for maintaining optimal physical properties of membranes that in turn are crucial for membrane function. The topic of this review is our current understanding of membrane phospholipid homeostasis in the reference eukaryote Saccharomyces cerevisiae. After introducing the physical parameters of the membrane that are kept in optimal range, the properties of the major membrane phospholipids and their contributions to membrane structure and dynamics are summarized. Phospholipid metabolism and known mechanisms of regulation are discussed, including potential sensors for monitoring membrane physical properties. Special attention is paid to processes that maintain the phospholipid class specific molecular species profiles, and to the interplay between phospholipid class and acyl chain composition when yeast membrane lipid homeostasis is challenged. Based on the reviewed studies, molecular species selectivity of the lipid metabolic enzymes, and mass action in acyl-CoA metabolism are put forward as important intrinsic contributors to membrane lipid homeostasis.
Topics: Acyl Coenzyme A; Fatty Acids; Membrane Lipids; Phosphatidic Acids; Phospholipids; Saccharomyces cerevisiae
PubMed: 23631861
DOI: 10.1016/j.plipres.2013.04.006