Membrane protein distribution
Dotaz
Zobrazit nápovědu
Several peripheral membrane proteins are known to form membrane pores through multimerization. In many cases, in biochemical reconstitution experiments, a complex distribution of oligomeric states has been observed that may, in part, be irrelevant to their physiological functions. This phenomenon makes it difficult to identify the functional oligomeric states of membrane lipid interacting proteins, for example, during the formation of transient membrane pores. Using fibroblast growth factor 2 (FGF2) as an example, we present a methodology applicable to giant lipid vesicles by which functional oligomers can be distinguished from nonspecifically aggregated proteins without functionality. Two distinct populations of fibroblast growth factor 2 were identified with (i) dimers to hexamers and (ii) a broad population of higher oligomeric states of membrane-associated FGF2 oligomers significantly distorting the original unfiltered histogram of all detectable oligomeric species of FGF2. The presented statistical approach is relevant for various techniques for characterizing membrane-dependent protein oligomerization.
... Biological membranes 86 -- 2.3.2.2. Artificial membranes 95 -- 2.3.3. ... ... Lipid—protein interactions and membrane structure. 101 -- 2.4. Assembly of membranes 107 -- 2.5. ... ... Isolation of membranes 119 -- 2.7. ... ... Binding proteins 238 -- 4.5. ... ... A simple membrane equilibrium and membrane potentials 243 -- 5.1.2. ...
348 s. : il.
- Klíčová slova
- Membrány buněčné,
- MeSH
- buněčná membrána MeSH
- Konspekt
- Biochemie. Molekulární biologie. Biofyzika
- NLK Obory
- fyzika, biofyzika
- biochemie
OBJECTIVE: The distribution of different antidepressants between plasma and red blood cells (RBCs) or between water and erythrocyte membranes (ghosts) has not been sufficiently compared so far. MATERIALS AND METHODS: Distribution of seven antidepressants (amitriptyline, nortriptyline, imipramine, desipramine, didesmethylimipramine, dothiepin, and citalopram) was measured in vitro in small volumes of blood or erythrocyte membrane suspension using radiolabeled drugs. Blood samples were taken from healthy subjects. RESULTS: The distribution of antidepressants between plasma and RBCs is strongly affected by temperature; however, it does not depend on the antidepressant concentration in the range of their therapeutic concentrations. The data analysis proved that the ratio of RBCs to plasma volume concentrations is the suitable parameter characterizing antidepressant distribution in whole blood. Significantly higher ratios of RBCs to plasma concentrations were found for demethylated metabolites of tricyclic antidepressants and in the case of citalopram. Citalopram showed the highest accumulation in intact RBCs and at the same time the lowest binding to isolated membranes. The binding of drugs to isolated erythrocyte membranes was much higher than in whole blood. CONCLUSION: The concentration ratio of antidepressant in RBCs and in plasma is sensitive not only to the binding properties of plasma proteins and cell membranes, but also to changes in drug molecule, both in aminopropyl chain and in aromatic rings. This ratio is to a large extent characteristic of a particular antidepressant.
Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of "equilibrative nucleoside transporters" and "purine permeases", which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness.
- MeSH
- Arabidopsis metabolismus MeSH
- biologický transport MeSH
- buněčná membrána metabolismus MeSH
- cytokininy metabolismus MeSH
- homeostáza MeSH
- hydrofobní a hydrofilní interakce MeSH
- kinetika MeSH
- kořeny rostlin metabolismus MeSH
- membránové transportní proteiny metabolismus MeSH
- proteiny huseníčku genetika MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus MeSH
- signální transdukce fyziologie MeSH
- termodynamika MeSH
- výhonky rostlin metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
II, 140 s. : tab., grafy
Cellular senescence, induced by genotoxic or replication stress, is accompanied by defects in nuclear morphology and nuclear membrane-heterochromatin disruption. In this work, we analyzed cytological and molecular changes in the linker of nucleoskeleton and cytoskeleton (LINC) complex proteins in senescence triggered by γ-irradiation. We used human mammary carcinoma and osteosarcoma cell lines, both original and shRNA knockdown clones targeting lamin B receptor (LBR) and leading to LBR and lamin B (LB1) reduction. The expression status and integrity of LINC complex proteins (nesprin-1, SUN1, SUN2), lamin A/C, and emerin were analyzed by immunodetection using confocal microscopy and Western blot. The results show frequent mislocalization of these proteins from the nuclear membrane to cytoplasm and micronuclei and, in some cases, their fragmentation and amplification. The timing of these changes clearly preceded the onset of senescence. The LBR deficiency triggered neither senescence nor changes in the LINC protein distribution before irradiation. However, the cytological changes following irradiation were more pronounced in shRNA knockdown cells compared to original cell lines. We conclude that mislocalization of LINC complex proteins is a significant characteristic of cellular senescence phenotypes and may influence complex events at the nuclear membrane, including trafficking and heterochromatin attachment.
- MeSH
- časoprostorová analýza MeSH
- jaderný obal metabolismus MeSH
- lidé MeSH
- membránové proteiny metabolismus MeSH
- receptory cytoplazmatické a nukleární genetika MeSH
- stárnutí buněk genetika MeSH
- záření gama terapeutické užití MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The transverse (t-) tubules of cardiac ventricular myocytes are invaginations of the surface membrane that form a complex network within the cell. Many of the key proteins involved in excitation-contraction coupling appear to be located predominantly at the t-tubule membrane. Despite their importance, the fraction of cell membrane within the t-tubules remains unclear: measurement of cell capacitance following detubulation suggests approximately 32%, whereas optical measurements suggest up to approximately 65%. We have, therefore, investigated the factors that may account for this discrepancy. Calculation of the combinations of t-tubule radius, length and density that produce t-tubular membrane fractions of 32% or 56% suggest that the true fraction is at the upper end of this range. Assessment of detubulation using confocal and electron microscopy suggests that incomplete detubulation can account for some, but not all of the difference. High cholesterol, and a consequent decrease in specific capacitance, in the t-tubule membrane, may also cause the t-tubule fraction calculated from the loss of capacitance following detubulation to be underestimated. Correcting for both of these factors results in an estimate that is still lower than that obtained from optical measurements suggesting either that optical methods overestimate the fraction of membrane in the t-tubules, or that other, unknown, factors, reduce the apparent fraction obtained by detubulation. A biophysically realistic computer model of a rat ventricular myocyte, incorporating a t-tubule network, is used to assess the effect of the altered estimates of t-tubular membrane fraction on the calculated distribution of ion flux pathways.
- MeSH
- financování organizované MeSH
- kardiomyocyty chemie metabolismus MeSH
- krysa rodu rattus MeSH
- proteiny analýza metabolismus MeSH
- sarkolema chemie metabolismus MeSH
- sarkoplazmatické retikulum chemie metabolismus MeSH
- srdeční komory cytologie chemie metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- přehledy MeSH
