Plasmalemma ATPase

Petel, G. and Gendraud, M., Biochemical properties of the plasmalemma ATPase of Jerusalem artichoke (Helianthus tuberosus L.) tubers in relation to dormancy, Plant Cell Physiol., 29, 739-741, 1988. 

OH, NH2, SH groups glutamine synthetase plasmalemma ATPase coupling factor 1 mitochondrial membrane aspartate carbamoyl-transferase... 

Sucrose absorption by the conducting tissue of the Cyclamen petiole has been shown to be a carrier-mediated step accomplished by cotransport with protons (5). Stimulated sucrose absorpt ion in the presence of brassinosteroids as observed in this investigation may, therefore, be attributed to a higher proton pump activity of the plasmalemma ATPase. 

Parasympathomimetics and sym-pathomimetics act at membrane receptors for visceromotor neurotransmitters. The plasmalemma also harbors the sites of action of cardiac glycosides (the Na/K-ATPases, p. 130), of Ca + antagonists (Ca2+ channels, p. 122), and of agents that block Na channels (local anesthetics p. 134, p. 204). An intracellular site is the target for phosphodiesterase inhibitors (e.g., amrinone, p. 132). 

Pinton, R., Cesco, S., Iacolettig, G, Astolfi, S., and Varanini, Z. (1999a). Modulation of NOj uptake by water-extractable humic substances Involvement of root plasmalemma H+ ATPase. Plant Soil 215,155-161. 

The outer membrane, the plasmalemma, efficiently protects the cell from the environment while, at the same time, carrying out functions important for cell metabolism the uptake of substrates and the elimination of toxic compounds. Substrate exchange with the environment is controlled by transport proteins embedded in the membrane (energy-requiring pumps such as Na+,K+-ATPase, or other transport units such as the Na+/glucose cotransporter and sodium and calcium ion channels) [1],... 

A.2 Plasnrnlemnud Ca -ATPase Pump Ca is extruded extracellularly from the cytosol by a Mg -dependent Ca, H -ATPase pump (Hogaboom and Fedan, 1981). This is an electrically neutral process by which Ca is exchanged ft)r 2H. In resting smooth muscle the Ca " pump exists in a low affinity state which is capable of extruding sufficient Ca " to maintain steady state in the fece of Ca influx across the plasmalemma down its concentration gradient via the passive leak mechanism (Carafoli, 1984). 

Using guard or mesophyll cell protoplasts of Comme-lina, in an assay according to (4), activities of solubilized plasmalemma and tonoplast ATPase were found unchanged after steroid treatment. 

Nevertheless, it was clearly demonstrated that bras-sinosteroids, like the other steroids investigated here, interact with the plasmalemma thereby showing short-term effects on the membrane potential and/or medium acidification. In some cases these effects correlate with stomata 1 movement and solute uptake into leaves or conducting tissue. The results are compatible with an effect of these substances on the membrane-embedded moiety of the plasmalemma H -ATPase yielding a modified proton pump rate. They support, therefore, the "Annulus Hypothesis" according to which sterol effects are caused by direct lipid-protein binding. 

Gibrat, R., Grouzis, J.-P., Rigaud, J., Grignon, C., 1985. Electrostatic characteristics of com root plasmalemma effect on the Mg +-ATPase activity. Biochim. Biophys. Acta 816, 349-357. 

ATP is cleaved by most sarcoplasmic reticulum preparations at low rates in the absence of calcium ions. This activity has been denoted as basal activity [20]. When calcium accumulation is initiated, ATP is rapidly hydrolyzed in a calcium-dependent activity, reaching its optimum at a calcium concentration of 10 jaM, and which is severely suppressed by the rising calcium concentrations in the interior of the vesicles [45,64,65]. The calcium-dependent activity was early characterized as the activity of an enzyme distinctly different from the calcium-independent enzyme. In contrast to the calcium-dependent ATPase, the calcium-independent enzyme is quite insensitive to thiol or amino group reagents. Conversely, the calcium-independent activity can be abolished by low concentrations of detergents which do not reduce the activity of the calcium-dependent enzyme [66]. The two enzymatic activities further differ in their nucleotide specificity and affinity, as well as in their magnesium and temperature dependences. The basal activity most likely originates from plasmalemma and T-tubules membranes [41]. 

Membraneous structures play a crucial role in the organization of the yeast cell. The membrane (plasmalemma) is some 8 nm thick and is invaginated to protrude into the cytoplasm. The plasmalemma is the site of cell wall synthesis, excretion of metabolites, secretion of extracellular enzymes and the regulated uptake of nutrients. Enzymes responsible for transporting nutrients are located in the membrane which also exhibits an ATPase activity which may be involved in the movement of molecules against concentration gradients. 

Adenosine triphosphatase (ATPase) was localised in the plasmalemma of guinea pig peritoneal macrophages (North 1966). Enzymatic activity could be removed from the cells by trypsin. While scanning electron microscopy of endothelial cells monolayers harvested using 0.25% trypsin or 0.125 % trypsin + 0.01 % EDTA failed to reveal any distinctive differences in their surface morphology (Kirkpatrick et al. 1986), bovine alveolar macrophages showed blebbing (Brehm 1996). 

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