Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated sarcoplasmic reticulum vesicles from rabbit white muscle were separated into a light (15--20% of total microsomes) and a heavy (80--85%) fraction by density gradient centifugation. The ultrastructure, chemical composition, enzymic activities and localization of membrane components in the vesicles of both fractions were investigated. From the following results it was concluded that both fractions are derived from the membranes of the sarcoplasmic reticulum system of the muscle: (i) The protein pattern of both fractions is essentially the same, except for different ratios of acidic, Ca2+-binding proteins. (ii) The 105000 dalton protein of the light fraction cross-reacts immunologically with the Ca2+-dependent ATPase of the heavy fraction. (iii) Ca2+-dependent ATPase, although of different specific activity, is found in both fractions. After rendering the vesicles leaky, specific activities in both fractions reach the same value. The light fraction was found to consist of "inside-out" vesicles by the following criteria: (i) No Ca2+ accumulation can be measured and the Ca2+-dependent ATPase activity is low and variable. (ii) The rate of trypsin digestion is lower and, compared to the heavy microsomes, a different ratio of degradation products is obtained. (iii) The sarcoplasmic reticulum membrane has a highly asymmetrical lipid distribution. This distribution of aminophospholipids is opposite to that in vesicles of heavy fraction. The light sarcoplasmic reticulum fraction has a higher phospholipid to protein ratio than the heavy one. This is consistent with the possibility that the two fractions derive from different parts of the sarcoplasmic reticulum system.
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PMID:Studies on the heterogeneity of sarcoplasmic reticulum vesicles. 15 48

p-Nitrophenyl phosphatase (p-NPPase) activity of (Na+-K+)-activated adenosine triphosphatase ((Na+-K+)-ATPase) on the acinar cells of dog submandibular gland was demonstrated by using light microscopy. The reaction products of p-NPPase of fresh frozen sections were seen to be localized on the basal parts of acini, and disappeared when the sections were incubated in medium containing 10(-3) Mouabain or in a K-free medium. Under the electron microscope, the reaction products of ATPase were found to be localized on the basolateral plasma membrane of both serous and mucous cells. On the microvilli of the luminal plasma membrane of the acinar cell, a small quantity of the reaction products was also present. This localization of ATPase reaction products on the serous and mucous cells seemed to coincide well with that of p-NPPase activity observed on the acini under light microscopy. Possible explanations are given regarding distribution of the above mentioned enzymes in relation to the cation transport of the plasma membrane. Structural and functional asymmetrical properties of acinar cells of the dog submandibular gland are also discussed.
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PMID:Histochemical and cytochemical localization of (Na+-K+)-activated adenosine triphosphatase in the acini of dog submandibular glands. 21 93

The peripheral membrane protein fraction released by washing Acholeplasma laidlawii membranes with low-ionic strength buffers contained about 50% of the total membrane-bound ribonuclease and deoxyribonuclease activities. The ATPase, NADH oxidase and p-nitrophenylphosphatase activities remained bound to the membrane even when EDTA was added to the wash fluids, and thus appear to belong to the integral membrane protein group. Serving as a marker for peripheral membrane proteins, the membrane-bound ribonuclease activity was solubilized by bile salts much more effectively than the integral membrane-bound enzymes. On the other hand, the solubilized ribonuclease showed a much lower capacity to reaggregate with other solubilized membrane components to membranous structures. Yet, most of the ribonuclease molecules which were bound to the reaggregated membranes could not be released by low-ionic strength buffer. The reaggregated membranes differed from the native membranes in the absence of particles on their fracture faces obtained by freeze cleaving, and by their much higher labeling by the [125-I]lactoperoxidase iodination system. These results suggest that most of the proteins are exposed on the reaggregated membrane surfaces, with very little, if any, protein embedded in its lipid bilayer core. Enzyme disposition in the A. laidlawii membrane was studied by comparing the activity of isolated membranes with that of membranes of intact cells after treatment with pronase or with an antiserum to membranes. The data indicate the asymmetrical disposition of these activities, the ATPase and NADH oxidase being localized on the inner membrane surface, while the nucleases are exposed on the external membrane surface.
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PMID:Characterization of the mycoplasma membrane proteins. V. Release and localization of membrane-bound enzymes in Acholeplasma laidlawii. 23 52

The mechanism of GroEL (chaperonin)-mediated protein folding is only partially understood. We have analysed structural and functional properties of the interaction between GroEL and the co-chaperonin GroES. The stoichiometry of the GroEL 14mer and the GroES 7mer in the functional holo-chaperonin is 1:1. GroES protects half of the GroEL subunits from proteolytic truncation of the approximately 50 C-terminal residues. Removal of this region results in an inhibition of the GroEL ATPase, mimicking the effect of GroES on full-length GroEL. Image analysis of electron micrographs revealed that GroES binding triggers conspicuous conformational changes both in the GroES adjacent end and at the opposite end of the GroEL cylinder. This apparently prohibits the association of a second GroES oligomer. Addition of denatured polypeptide leads to the appearance of irregularly shaped, stain-excluding masses within the GroEL double-ring, which are larger with bound alcohol oxidase (75 kDa) than with rhodanese (35 kDa). We conclude that the functional complex of GroEL and GroES is characterized by asymmetrical binding of GroES to one end of the GroEL cylinder and suggest that binding of the substrate protein occurs within the central cavity of GroEL.
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PMID:Chaperonin-mediated protein folding: GroES binds to one end of the GroEL cylinder, which accommodates the protein substrate within its central cavity. 136 Nov 69

The mucosa that lines the airways is covered with a fluid film forming a hypophase between mucus and cell surface. To study the function of this epithelium aims at describing the mechanisms by which fluid is normally produced. Another goal to be pursued consists in looking for the origin of pathological situations, such as cystic fibrosis, in which the functioning of epithelial cell is altered. The elucidation of transport mechanisms present in the apical and in the basolateral membrane results in a conceptual model that illustrates the asymmetrical functioning of epithelial cells. Recent discoveries enlarge our understanding of membrane transport processes; in particular, a concerted, reciprocal regulation of the activity of both membranes was shown to be exerted via the intracellular composition. The tracheal epithelium absorbs Na+ and secretes Cl-. These two transports are active and electrogenic; their sum corresponds approximately to the short-circuit current measured in vitro. Na+ absorption is sensitive to amiloride from the luminal side and also to ouabain added to the serosal compartment. The process is a primary active transport, analogous to that found in amphibian epithelia or in mammalian colon. Cl- secretion is abolished by furosemide (or bumetanide), by ouabain or by Na+ suppression in the serosal incubation solution. The mechanism is a secondary active transport: Cl- influx across the basolateral membrane is coupled to Na+ (probably through Na+, K+, Cl- symport); energy is dissipated by the Na+-K+-ATPase localised in the basolateral membrane. Thus, Na+ is recirculated across that membrane by the pump activity, which maintains a favorable gradient for influx via the symport. Cl- efflux takes place by diffusion through the luminal membrane. This model applies to other epithelia in which Na+-coupled Cl- secretion was shown to take place. It is confirmed by isotopic fluxes measurements and by electrophysiologic properties of the apical and the basolateral membrane. Various agents are known to influence ion transports. In particular Cl- secretion is stimulated by substances that increase the intracellular concentration of cyclic AMP. At the membrane level, the number of active Cl- channels in the apical membrane is primarily controlled, then the basolateral membrane K+ permeability. Yet, species differences are worth to note: the trachea of the cow is barely sensitive to agents that exert a marked action on dog trachea. The tracheal epithelium is used as an experimental model for studying cystic fibrosis, a disease in which the apical membrane is almost devoid of functional Cl- channels, so that Cl- permeability is quite low.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Physiology of the tracheal epithelium]. 246 15

Proteins exposed on the cytoplasmic face of isolated chromaffin granules were labelled by lactoperoxidase-catalysed radioiodination and by non-enzymic biotinylation. Granule membranes were then prepared, and the H+-translocating ATPase isolated by fractionation with Triton X-114. The labelling of individual ATPase subunits was assessed by polyacrylamide-gel electrophoresis, followed by autoradiography or by blotting and decoration with 125I-labelled streptavidin. Subunits of 72, 57 and kDa were strongly labelled, and could be removed from the membrane at pH 11: they are therefore extrinsic proteins. The 120 kDa subunit was also labelled, but it was not solubilized at pH 11. Photolabelling with a hydrophobic probe indicated that this subunit penetrates the bilayer, and enzymic degradation studies showed the presence of N-linked oligosaccharides; this subunit therefore spans the chromaffin-granule membrane. Labelling of the 17 kDa subunit occurred predominantly on the extracytoplasmic (matrix) face of the granule membrane. These results are consistent with this V-type ATPase having a structure that is generally similar to that of mitochondrial (F-type) ATPases, although the attachment of the 120 kDa subunit may be asymmetrical.
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PMID:Topography of a vacuolar-type H+-translocating ATPase: chromaffin-granule membrane ATPase I. 253 3

The purpose of this investigation was to study the effects of a distinct type of phospholipase C on sarcolemmal Na+-Ca2+ exchange. With this phospholipase C (Staphylococcus aureus), treatment of cardiac sarcolemmal vesicles resulted in a specific hydrolysis of membrane phosphatidylinositol. This hydrolysis of phosphatidylinositol also released two proteins (110 and 36 kDa) from the sarcolemmal membrane. Phospholipase C pretreatment of the sarcolemma resulted in an unexpected stimulation of Na+-Ca2+ exchange. The Vmax of Na+-Ca2+ exchange was increased but the Km for Ca2+ was not altered. This stimulation was specific to the Na+-Ca2+ exchange pathway. ATP-dependent Ca2+ uptake was depressed after phospholipase C treatment, but passive membrane permeability to Ca2+ was unaffected. Sarcolemmal Na+,K+-ATPase activity was not altered, whereas passive Ca2+ binding was modestly decreased after phospholipase C pretreatment. The stimulation of Na+-Ca2+ exchange after phosphatidylinositol hydrolysis was greater in inside-out vesicles than in a total population of vesicles of mixed orientation. This finding suggests that the cardiac sarcolemmal Na+-Ca2+ exchanger is functionally asymmetrical. The results also suggest that membrane phosphatidylinositol is inhibitory to the Na+-Ca2+ exchanger or, alternatively, this phospholipid may anchor an endogenous inhibitory protein in the sarcolemmal membrane. The observation that a transsarcolemmal Ca2+ flux pathway may be stimulated solely by phosphatidylinositol hydrolysis independently of phosphoinositide metabolic products like inositol triphosphate is novel.
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PMID:Role of phosphatidylinositol in cardiac sarcolemmal membrane sodium-calcium exchange. 254 59

Purified Na/K-ATPase from guinea pig renal outer medulla has been delipidated and solubilized in Brij 58 (polyoxyethylene ether; C-16, E-20). At a concentration of 2 mg of Brij 58/mg of protein, about one-half the enzyme complement was solubilized and almost 50% of Na/K-ATPase activity was retained by the enzyme-micelle complex. Guinier plots of the neutron scattering profiles yielded no evidence of heterogeneity with respect to subunit composition or the state of aggregation in the solubilized oligomers. Contrast matching with D2O used to obtain estimates of the molecular weight of the micellar form of Na/K-ATPase gave a mean value of 310,000 +/- 42,700, which corresponds to an alpha 2 beta 2 tetramer. A Stuhrmann plot of the neutron scattering data yielded an estimated radius of gyration of 67 A. The Stuhrmann plot also indicated an asymmetrical distribution of neutron scattering density. On the basis of the Stuhrmann plot parameters, the estimated molecular weight, and the radius of gyration, a low-resolution model was formulated of the oligomeric unit of Na/K-ATPase.
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PMID:Low-angle neutron scattering analysis of Na/K-ATPase in detergent solution. 302 64

The interaction between membrane proteins and cytoplasmic structural proteins is thought to be one mechanism for maintaining the spatial order of proteins within functional domains on the plasma membrane. Such interactions have been characterized extensively in the human erythrocyte, where a dense, cytoplasmic matrix of proteins comprised mainly of spectrin and actin, is attached through a linker protein, ankyrin, to the anion transporter (Band 3). In several nonerythroid cell types, including neurons, exocrine cells and polarized epithelial cells homologues of ankyrin and spectrin (fodrin) are localized in specific membrane domains. Although these results suggest a functional linkage between ankyrin and fodrin and integral membrane proteins in the maintenance of membrane domains in nonerythroid cells, there has been little direct evidence of specific molecular interactions. Using a direct biological and chemical approach, we show here that ankyrin binds to the ubiquitous (Na+ + K+)ATPase, which has an asymmetrical distribution in polarized cells.
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PMID:Ankyrin binding to (Na+ + K+)ATPase and implications for the organization of membrane domains in polarized cells. 303 71

Using 3H-ouabain autoradiography, Na+-K+-ATPase has been localized on the basolateral membranes of ciliated and nonciliated cells in the oviduct (pars recta, p. convoluta I, II, III) of the European fire salamander, Salamandra salamandra. The mucous and seromucous gland cells of the p. convoluta I, II, III, however, do not show any significant labelling. An asymmetrical distribution of ouabain binding sites is a main feature of transporting epithelia.
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PMID:Na-pump sites in the oviduct of Salamandra salamandra (L.) (Amphibia, Urodela). 626 38


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