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What Are The Functions Of Membrane Proteins
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Regulation Of Membrane Protein Structure And Function By Their Lipid Nano Environment
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Received: June 13, 2022 / Revised: June 25, 2022 / Accepted: June 28, 2022 / Published: June 29, 2022
Membrane proteins embedded in biological membranes account for 30% of the proteins encoded in the human genome and play an important role in maintaining cell homeostasis through, among other things, transporters, signaling and energy conversion. Therefore, knowledge of the atomic density structure of membrane proteins is crucial for understanding their function. However, it is difficult to determine the structure of membrane proteins at atomic resolution due to their degree of crystallinity compared to soluble proteins.
The Role Of Membrane Destabilisation And Protein Dynamics In Bam Catalysed Omp Folding
Recent developments in structure determination methods have led to high-resolution structures of membrane proteins, and many high-resolution structures of membrane proteins have already been reported (4% of the preliminary budget). Solid-state NMR spectroscopy does not require crystallization and is not limited by the molecular weight or structure of the liver membrane protein to be determined . Solution NMR spectroscopy has recently been used to determine the structure of membrane proteins, using detergent micelles or nanosheets as membrane mimic systems . In X-ray crystallography, it becomes possible to determine the structure of membrane proteins using membranes or membrane mimic systems to form crystals . Recently developed time-resolved methods make it possible to determine the short-lived intermediate structures of membrane proteins . The focus is on cryo-electron microscopy (cryo-EM), a powerful technique for determining the structure of membrane proteins using two-dimensional crystals . Recently, it became possible to determine the structure of membrane proteins based on single-molecule cryo-EM observations .
This special issue focuses on methodological developments, including advanced investigations of structure-function relationships using advanced methods for high-resolution structure determination of membrane proteins. In this special issue, in addition to defining the overall structure summarized in Figure 1, we also identify functions related to local conformational changes and dynamic properties of membrane proteins.
In this special issue, Florian Seimer et al.  reported that one of the transmembrane helices of human carbonic anhydrase XII membrane protein contains many small side chain amino acids, suggesting that these small amino acids play an important role in the dimerization of the transmembrane domain. Using the GALLEX assay, the authors showed that the transmembrane domain forms strong transmembrane helical oligomers that are embedded in biological membranes. The authors also showed that single or multiple mutations of small isoleucine residues consistently increased the interaction propensity. Reduced helix flexibility and protein-lipid contacts increase the stability of helix-helix interactions within the membrane.
Ko Takeuchi et al.  focused on solution NMR to reveal the structural basis of function for many permeable membrane proteins, such as ion channels, GPCRs, and transporters. Furthermore, membrane proteins exist in conformational equilibrium between different conformational states associated with different functional states. The relative populations of different conformational states can quantitatively reveal the function of a membrane protein under specific conditions. Exchange rates between different conformational states determined by solution NMR can determine the time scale of cell responses investigated in ion channels and GPCRs. Since solution NMR allows the detection and measurement of proton dynamics on different time scales and subatomic resolution, this technique is well suited to understand the function of multi-helical membrane proteins.
Improving Cell Free Glycoprotein Synthesis By Characterizing And Enriching Native Membrane Vesicles
Cuauhtemoc U. Gonzalez et al.  investigated the structural regulation of concanavalin A (Con-A) homomeric binding to GluK2 receptors. Con-A stabilizes the active open channel state of kainate receptors and reduces the degree of desensitization. In this study, the authors used single-molecule fluorescence resonance energy transfer (smFRET) techniques to investigate ground-state changes in Con-A kainate receptor modulation. These studies showed that Con-A binds to the Gluk2 receptor in the immediate vicinity of the subunit at the amino-terminal dimer-dimer interface and between the subunits of the agonist-binding domain. Based on these results, the authors concluded that the Con-A modulation of kainate receptor activity is mediated by the shift of the kainate receptor conformation towards the extracellular domain.
Saman Majid et al.  focuses on membrane mimics, which are the most widely used structural and functional studies of integral membrane proteins (IMPs) at the molecular level. These membrane mimics include detergents, liposomes, bicelles, nanodiscs/lipodiscs, amphipoles, and lipid cubic phases. The authors discuss the protocols for the recovery of IMPs in membrane mimics, as well as the applicability of these membrane mimic-IMP complexes in studies using various biochemical, biophysical, structural, and structural-biological methods. The diversity of these systems has increased significantly, and a wide range of lipid membrane-mimicking platforms provide the high solubility, stability, low and low lipid bilayer environments, and other unique properties used in studies using solution NMR and X-rays. crystallography, cryo-EM, ESR, fluorescence spectroscopic analysis, ligand binding and transfer analysis, etc.
Chung-Hao Liu et al.  investigated the effect of cholesterol on the interaction between viral protein R (Vpr) and lipid membranes. Using a calcium release assay, the authors found that membrane permeability induced by membrane binding of Vpr was significantly reduced in the presence of membrane cholesterol. Using solid-state NMR spectroscopy, Vpr has been shown to have a heterogeneous chemical environment.
The CO NMR signal of amino acid Cys-76 is between 165 and 178 ppm, which can be explained by the presence of several Vpr-membrane environments. The authors found that the presence of membrane cholesterol alters the distribution of Vpr in multiple membrane environments, which may explain Vpr-induced changes in membrane permeability in the presence of cholesterol.
Solved Drag The Labels To The Appropriate Locations In
Shinya Hanashima et al.  shows that molecular structural analysis of interactions between membrane proteins and lipids or detergents that make up biological and artificial model membranes is important for understanding the function and physicochemical properties of membrane proteins and biomembranes. Determining the structure of membrane proteins at the molecular level is much more difficult than that of soluble proteins, but new technical developments have accelerated the clarification of membrane protein structure-function relationships. The authors summarize the development of heavy atom derivative detergents and lipids for the structural analysis of membrane proteins at the molecular level and their application to short-lived intermediates by X-ray free electron laser crystallography.
Munehiro Kumashiro et al.  reported that the formation of β chain oligomers of the antimicrobial peptide maginin 2 (M2) contributed to the disruption of phospholipid membranes. The authors measured the circular dichroism and linear dichroism (LD) of M2 synchrotron radiation in lipid membranes and determined the shape and orientation of M2 on the membrane. Singularity decay analysis confirmed the presence of the intermediate state, and global conformational analysis showed that α-helical M2 monomers form β-strand-rich M2 oligomers in the intermediate state. LD spectra. Fluorescence spectroscopy showed that the formation of β-sized oligomers destabilizes the sealing structure of the membrane and induces calcium permeabilization. These results suggest that M2 β-chain oligomer formation plays an important role in cell membrane disruption.
Review: Nadezhda Barvitenko et al.  show that endothelial mechanosensors are key upstream signaling proteins in shear stress (SS)-induced inflammatory and anti-inflammatory responses. In the case of transmembrane proteins, mechanosensation is regulated by the biomechanical properties of the lipid bilayer and the cytoskeleton in addition to the SS sensing of the liquid. The authors emphasized the anti-inflammatory factors (hypoxia,