Interactions between protein molecules and the virus removal membrane surface: Effects of immunoglobulin G adsorption and conformational changes on filter performance

2017 ◽  
Vol 34 (2) ◽  
pp. 379-386 ◽  
Author(s):  
Ryo Hamamoto ◽  
Hidemi Ito ◽  
Makoto Hirohara ◽  
Ryongsok Chang ◽  
Tomoko Hongo-Hirasaki ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Immunoglobulin G ◽  
Membrane Surface ◽  
Surface Effects ◽  
Virus Removal ◽  
Filter Performance ◽  
Protein Molecules

Role of spectrin in membrane fusion and in shape change of human erythrocyte ghost

1978 ◽  
Vol 36 (2) ◽  
pp. 328-329
Author(s):  
Hideo Hayashi ◽  
Yoshikazu Hirai ◽  
John T. Penniston
Keyword(s):  
Conformational Changes ◽  
Human Erythrocyte ◽  
Shape Change ◽  
Membrane Surface ◽  
Slight Modification ◽  
Active Role ◽  
Main Role ◽  
Bank Blood ◽  
Human Erythrocyte Ghost

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.

Function-related conformational changes of protein molecules revealed by Raman spectroscopy

1999 ◽  
pp. 13-14
Author(s):  
Andrey Yu. Chikishev ◽  
Cees Otto ◽  
Nikolai N. Brandt ◽  
Vladislav V. Molodozhenya ◽  
Inna K. Sakodynskaya ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Conformational Changes ◽  
Protein Molecules

Binding of Antibodies onto the Thylakoid Membrane II. Distribution of Lipids and Proteins at the Outer Surface of the Thylakoid Membrane

1977 ◽  
Vol 32 (7-8) ◽  
pp. 597-599 ◽  
Author(s):  
Alfons Radunz
Keyword(s):  
Outer Surface ◽  
Thylakoid Membrane ◽  
Membrane Surface ◽  
Phosphatidyl Glycerol ◽  
Protein Molecules ◽  
Specific Antisera ◽  
Accessible Surface ◽  
The Individual ◽  
Monogalactosyl Diglyceride ◽  
Cover Up

Abstract The number of antibody molecules which stroma-freed chloroplasts can bind out of the mono-specific antisera to monogalactosyl diglyceride, tri-and digalactosyl diglyceride, sulfoquinovosyl diglyceride, phosphatidyl glycerol, sitosterol, plastoquinone, lutein and neoxanthin was determined. This number was compared to the number of antibody molecules which stroma-freed chloroplasts can maximally bind. The result is that the antibodies to the individual lipids cover at most 17 per cent of the accessible thylakoid membrane surface. From a serum which contains both antibodies to the proteins and lipids of the thylakoid membrane, not more antibody molecules are bound than from a serum to the proteins. This means that antibodies to proteins are able to cover up the entire accessible surface of the thylakoids whereas a mixture of antibodies to the lipids, listed above, cover only one forth of the surface. Consequently, antibodies which are bound to proteins can cover up the lipid areas entirely and in turn antibodies which are bound to lipids cover up parts of the protein areas. From this it follows that the portion of the surface, which is made up by lipids must be considerably smaller than 24 per cent. Furthermore, it follows from these experiments that the lipid areas are small and that lipids probably only fill up the gaps between the protein molecules.

scholarly journals Constraining the Lateral Helix of Respiratory Complex I by Cross-linking Does Not Impair Enzyme Activity or Proton Translocation

2015 ◽  
Vol 290 (34) ◽  
pp. 20761-20773 ◽  
Author(s):  
Shaotong Zhu ◽  
Steven B. Vik
Keyword(s):  
Conformational Changes ◽  
Complex I ◽  
Nadh Oxidase ◽  
Membrane Surface ◽  
Proton Translocation ◽  
Membrane Vesicles ◽  
Peripheral Region ◽  
Significant Loss ◽  
Cysteine Residues ◽  
Nadh:Ubiquinone Oxidoreductase

Complex I (NADH:ubiquinone oxidoreductase) is a multisubunit, membrane-bound enzyme of the respiratory chain. The energy from NADH oxidation in the peripheral region of the enzyme is used to drive proton translocation across the membrane. One of the integral membrane subunits, nuoL in Escherichia coli, has an unusual lateral helix of ∼75 residues that lies parallel to the membrane surface and has been proposed to play a mechanical role as a piston during proton translocation (Efremov, R. G., Baradaran, R., and Sazanov, L. A. (2010) Nature 465, 441–445). To test this hypothesis we have introduced 11 pairs of cysteine residues into Complex I; in each pair one is in the lateral helix, and the other is in a nearby region of subunit N, M, or L. The double mutants were treated with Cu2+ ions or with bi-functional methanethiosulfonate reagents to catalyze cross-link formation in membrane vesicles. The yields of cross-linked products were typically 50–90%, as judged by immunoblotting, but in no case did the activity of Complex I decrease by >10–20%, as indicated by deamino-NADH oxidase activity or rates of proton translocation. In contrast, several pairs of cysteine residues introduced at other interfaces of N:M and M:L subunits led to significant loss of activity, in particular, in the region of residue Glu-144 of subunit M. The results do not support the hypothesis that the lateral helix of subunit L functions like a piston, but rather, they suggest that conformational changes might be transmitted more directly through the functional residues of the proton translocation apparatus.

scholarly journals Surface biofunctionalization with liquid-phase plasma treatment of collagen molecules

2021 ◽  
Author(s):  
Shiori Tanaka ◽  
Shingo Kanemura ◽  
Masaki Okumura ◽  
Kazuyuki Iwaikawa ◽  
Kenichi Funamoto ◽  
...  
Keyword(s):  
Surface Modification ◽  
Liquid Phase ◽  
Plasma Treatment ◽  
Conformational Changes ◽  
Plasma Discharge ◽  
Technical Limitation ◽  
Protein Molecules ◽  
Collagen Molecules ◽  
Versatile Technique ◽  
Liquid Phase Plasma

Abstract Surface functionalization is a key process in rendering various materials biocompatible. Whereas a number of techniques and technologies have been developed for the purpose of biofunctionalization, plasma treatment enables highly efficient surface modification. Extending plasma treatment to biomolecules in the liquid phase will control biofunctionalization via a simple process. However, interactions between plasma discharge and biomolecules or solvents are poorly understood, potentially leading to the technical limitation as to the utility of plasma treatment. In this study, we developed a technology for substrate biofunctionalization that does not require surface modification but involves direct treatment of a collagen molecules with liquid-phase plasma discharge. Biofunctionalization of collagen by plasma treatment comprises three processes that increase its reactivity with hydrophobic substrates: (1) charge-dependent changes in surface and interfacial properties of the collagen solution; (2) local conformational changes of the collagen molecules without their global structural alterations; and (3) induction of a micelle-like association formed by collagen molecules. We anticipate such plasma-induced functionalization of protein molecules to provide a versatile technique in the applications of biomaterials, including those related to pharmaceuticals and cosmetics.

scholarly journals Crystallization, structure and dynamics of the proton-translocating P-type ATPase

2000 ◽  
Vol 203 (1) ◽  
pp. 147-154
Author(s):  
G.A. Scarborough
Keyword(s):  
Conformational Changes ◽  
Crystal Packing ◽  
Membrane Surface ◽  
Transmembrane Helix ◽  
Carbon Films ◽  
Crystallographic Analysis ◽  
Two Dimensional ◽  
Structure And Dynamics ◽  
Sequence Of Events ◽  
Detergent Interactions

Large single three-dimensional crystals of the dodecylmaltoside complex of the Neurospora crassa plasma membrane H(+)-ATPase (H(+) P-ATPase) can be grown in polyethylene-glycol-containing solutions optimized for moderate supersaturation of both the protein surfaces and detergent micellar region. Large two-dimensional H(+) P-ATPase crystals also grow on the surface of such mixtures and on carbon films located at such surfaces. Electron crystallographic analysis of the two-dimensional crystals grown on carbon films has recently elucidated the structure of the H(+) P-ATPase at a resolution of 0.8 nm in the membrane plane. The two-dimensional crystals comprise two offset layers of ring-shaped ATPase hexamers with their exocytoplasmic surfaces face to face. Side-to-side interactions between the cytoplasmic regions of the hexamers in each layer can be seen, and an interaction between identical exocytoplasmic loops in opposing hexamer layers holds the two layers together. Detergent rings around the membrane-embedded region of the hexamers are clearly visible, and detergent-detergent interactions between the rings are also apparent. The crystal packing forces thus comprise both protein-protein and detergent-detergent interactions, supporting the validity of the original crystallization strategy. Ten transmembrane helices in each ATPase monomer are well-defined in the structure map. They are all relatively straight, closely packed, moderately tilted at various angles with respect to a plane normal to the membrane surface and average approximately 3.5 nm in length. The transmembrane helix region is connected in at least three places to the larger cytoplasmic region, which comprises several discrete domains separated by relatively wide, deep clefts. Previous work has shown that the H(+) P-ATPase undergoes substantial conformational changes during its catalytic cycle that are not changes in secondary structure. Importantly, the results of hydrogen/deuterium exchange experiments indicate that these conformational changes are probably rigid-body interdomain movements that lead to cleft closure. When interpreted within the framework of established principles of enzyme catalysis, this information on the structure and dynamics of the H(+) P-ATPase molecule provides the basis of a rational model for the sequence of events that occurs as the ATPase proceeds through its transport cycle. The forces that drive the sequence can also be clearly stipulated. However, an understanding of the molecular mechanism of ion transport catalyzed by the H(+) P-ATPase awaits an atomic resolution structure.

scholarly journals Cryo-EM analysis of PIP2 regulation in mammalian GIRK channels

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Yiming Niu ◽  
Xiao Tao ◽  
Kouki K Touhara ◽  
Roderick MacKinnon
Keyword(s):  
Conformational Changes ◽  
Cytoplasmic Membrane ◽  
Membrane Surface ◽  
Cytoplasmic Domain ◽  
Inward Rectifier ◽  
Particle Analysis ◽  
Single Particle Analysis ◽  
Girk Channels ◽  
Binding Surface ◽  
To Receive

G-protein-gated inward rectifier potassium (GIRK) channels are regulated by G proteins and PIP2. Here, using cryo-EM single particle analysis we describe the equilibrium ensemble of structures of neuronal GIRK2 as a function of the C8-PIP2 concentration. We find that PIP2 shifts the equilibrium between two distinguishable structures of neuronal GIRK (GIRK2), extended and docked, towards the docked form. In the docked form the cytoplasmic domain, to which Gβγ binds, becomes accessible to the cytoplasmic membrane surface where Gβγ resides. Furthermore, PIP2 binding reshapes the Gβγ binding surface on the cytoplasmic domain, preparing it to receive Gβγ. We find that cardiac GIRK (GIRK1/4) can also exist in both extended and docked conformations. These findings lead us to conclude that PIP2 influences GIRK channels in a structurally similar manner to Kir2.2 channels. In Kir2.2 channels, the PIP2-induced conformational changes open the pore. In GIRK channels, they prepare the channel for activation by Gβγ.

scholarly journals Structural Basis of Vitamin K Antagonism

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 482-482
Author(s):  
Weikai Li ◽  
Shixuan Liu ◽  
Shuang Li
Keyword(s):  
Vitamin K ◽  
Conformational Changes ◽  
Conflicts Of Interest ◽  
Bone Mineralization ◽  
Vitamin K Antagonists ◽  
Membrane Surface ◽  
Warfarin Dose ◽  
Binding Pocket ◽  
Structural Basis ◽  
Vitamin K Cycle

The vitamin K cycle supports blood coagulation, bone mineralization, and vascular calcium homeostasis. A key enzyme in this cycle, vitamin K epoxide reductase (VKOR), is the target of vitamin K antagonists (VKAs). Despite their extensive clinical use, the dose of VKAs (e.g., warfarin) is hard to regulate and overdose can lead to fatal bleeding. Improving the dose regulation requires understanding how VKAs inhibit VKOR, which is a membrane-embedded enzyme difficult to characterize with structural and biochemical studies. Here we achieve a long-standing goal of obtaining crystal structures of human VKOR with warfarin, which represents coumarin-based VKAs; with phenindione, which represents indandione-based VKAs; with superwarfarins, the most commonly used rodenticides; and with vitamin K epoxide in a reaction intermediate state. We have also solved structures of a VKOR-like homolog with warfarin, with vitamin K substrates, and without ligand. These structures show that human VKOR adopts an overall fold with four transmembrane helices (TM) and a large ER-luminal region. VKAs are bound at the active site of HsVKOR, which is formed by the surrounding four-TM bundle and a cap domain on top. The cap domain is stabilized by a linked anchor domain that interacts with the membrane surface. VKOR binds specifically to VKAs through hydrogen bonding to their diketone groups. Mutating VKOR residues recognizing the diketones render strong warfarin resistance. Except the hydrogen bonds, the binding pocket is largely hydrophobic. This pocket is incompatible with warfarin metabolite, explaining the inactivation of warfarin through CYP2C9 metabolism; CYP2C9 and VKOR genotypes can explain 30-50% of the patient variability in warfarin dose. In addition, the high potency of superwarfarins is due to the interaction of their side group with a tunnel where the isoprenyl chain of vitamin K is bound. For VKOR catalysis, the same residues affording the VKA-binding specificity also facilitate substrate reduction Initiation of the catalysis requires a reactive cysteine to form a substrate adduct. Interactions from this stably bound adduct induces a closed conformation, thereby triggering electron transfer to reduce the substrate. Importantly, the open to closed conformational change during catalysis similar to that induced by the binding of VKAs. Taken together, VKAs achieve inhibition through mimicking key interactions and conformational changes required for VKOR catalytic cycle. Understanding of these mechanisms will enable improved strategy to regulate warfarin dose and have a broad impact on thromboembolic diseases and bone disorders. Disclosures No relevant conflicts of interest to declare.

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