Plasma membrane ATPase

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

Multidrug resistance (MDR) is the name ascribed to the phenomenon whereby cancer cells and tumors develop resistance to chemotherapeutic agents. Conceptually, this can be viewed as a survival response whereby cancer cells endeavor to ward off cytotoxic compounds. Mechanistically, MDR is typically mediated by overexpression of P-glycoprotein (P-gp aka ABCB1) or other plasma membrane ATPases that export cytotoxic drugs used in chemotherapy, thereby reducing their efficacy. 

Flavonoids are known to inhibit the function of many ATP-binding proteins, such as mitochondrial ATPase, myosin, Na/K and Ca plasma membrane ATPases, protein kinases, topoisomerase II, and multidrug resistance (MDR) proteins. In general, inhibition takes place through binding of the flavonoids to the ATP-binding site. Only two cases relevant to the inhibition of carcinogenesis by flavonoids" " will be discussed in detail. 

Figure B3.4.1 Serial dilution of primary antibody directed against the 97-kDa catalytic subunit of the plant plasma membrane ATPase. The blot was developed with HRP-coupled avidin-biotin reagents according to the Alternate Protocol and visualized with 4-chloro-1-naphthol (4CN). Note how background improves with dilution...

Pmrl (for plasma-membrane ATPase-related) of Saccharomyces cerevisiae was the first intracellular Ca2+-ATPase that was identified as a member of the SPCA family (Rudolph et al., 1989 Antebi and Fink, 1992 Sorin et al 1997). There are no introns in the coding region, like for most genes in S. cerevisiae. The Pmrl protein (GenBank accession no. AAA34884) comprises of 950 amino acids and has a molecular weight of 104 kDa. 

Portillo, F. Serrano, R. (1989). Growth control strength and active site of yeast plasma membrane ATPase studied by site-directed mutagenesis. Eur. J. Biochem. 186, 501-507. 

ATPase activity was also studied by Friebe et al. in 1997.17 They correlated the BOA and DIBOA effects on radicle elongation of Avena sativa seedlings with their effects on the activity of plasma membrane H+-ATPase from roots of Avena sativa cv. Jumbo and from Vida faba cv. Alfred. They hypothesized that an alteration in the plasma membrane ATPase activity could be the reason for an abnormal nutrient absorption in plants exposed to hydroxamic acids, because of the role that this enzyme plays in the ion gradient and, therefore, in the ionic transport through plasma membrane. The results of this experiment showed a strong inhibition in the activity of this enzyme in the plasma membrane of chloroplast and mitochondria when it was exposed to BOA and DIMBOA. This alteration implies early interactions with the assayed hydroxamic acids. 

The objective of this study was also to establish a link between an easily observable allelopathic effect (growth inhibition of roots) and a cellular-based explanation (membrane permeability changes). Several modes of action can explain these results, such as an increase in the lipid peroxidation, a disruption in the intrinsic membrane protein activities, or an alteration in plasma membrane ATPase activity. 

Chaubron, F., Robert, F., Gendraud, M., and Petel, G., Partial purification and immunocytocharacterization of the plasma membrane ATPase of Jerusalem artichoke (Helianthus tuberosus L.) tubers in relation to dormancy, Plant Cell Physiol., 35, 1179-1184, 1994. 

Figure 9.29 Some mammalian (left) and microbial (right) membrane transport systems. (A) Primary electrogenic mechanisms (pumps) creating either a Na+ or a H+ gradient. (B) Secondary active transport systems of the symport type, in which the entry of a nutrient S into the cell is coupled with the entry of either the sodium ions or protons. (D) Various passive ion movements, possibly via channels or uniports. (Reproduced by permission from Serrano R. Plasma Membrane ATPase of Plants and Fungi. Boca Raton CRC Press, 1985, p. 59.)...

Efflux is blocked by compounds such as respiratory inhibitors that decrease levels of ATP. Apparently the influx-efflux mechanism is dependent on intracellular ATP, which is utilized by the plasma membrane ATPase and thus drives the efflux process (36). The synergistic effects of respiratory inhibitors could serve as the basis for using a combination of inhibitors. This also brings up the possibility that through the use of respiratory inhibitors, fungi that are normally insensitive or only slightly sensitive to fenarimol or imazalil due to efflux systems could be controlled. 

R. Serrano, M.C. Kielland-Brandt, G.R. Fink, Yeast Plasma Membrane ATPase Is Essential for Growth and Has Homology with (Na+ + K+), K and Ca -ATPase , Nature, 319, 689 (1986)... 

In liver plasma membranes, ATPase activities were determined as follows [1761. 

Due to the electrophilic nature of the molecules it is not surprising that DIBOA and DIMBOA were found to inactivate a number of enzymes unspecifically, such as aphid cholinesterase, UDP-glucosyltransferase, plasma membrane ATPase, chymotrypsin, papain, and ribonucleotide reductase [3]. One can speculate that a large number of cellular pathways, e.g., the ubiquitin-proteasome dependent selective protein degradation, where SH-groups of E-enzymes and lysine residues of target proteins are of crucial importance, may be affected [138]. 

In contrast to Egeria leaves, with Vida leaf slices, medium acidification was enhanced not only in the presence of SSHB but also by 24-E (Figure 1). The addition of the plasma membrane ATPase inhibitor erythro-sine B did strongly reduce brassinosteroid-induced H- -extrusion indicating that the stimulating effect of bras-sinosteroids is mediated by the ATP-driven proton pump. 

Roberg, K.J., Crotwell, M., Espenshade, P., Gimeno, R., and Kaiser, C. A. (1999). LST1 is a SEC24 homologue used for selective export of the plasma membrane ATPase from the endoplasmic reticulum./. Cell Biol. 145, 659-672. 

Fig.10.12). In P-ATPases (plasma membrane ATPases) and V-ATPases (vesicular ATPases), the chemical bond energy of ATP is used to reversibly phosphorylate the transport protein and change its conformation. For example, as Na, K -ATPase binds and cleaves ATP, it becomes phosphorylated and changes its conformation to release 3 Na ions to the outside of the cell, thereby building up a higher extracellular than intracellular concentration of Na. Na re-enters the cell on cotransport proteins that drive the uptake of amino acids and many other compounds into the cell. Thus, Na must be continuously transported back out. The expenditure of ATP for Na transport occurs even while we sleep and is estimated to account for 10 to 30% of our BMR.

Figure 19.5 Central role of the plasma membrane ATPase in the maintenance of proton homeostasis within the cytoplasm. Protons gain entry into the cytoplasm through passive proton diffusion, which can increase with increasing ethanol from the uptake of protonated acids from symport with amino acids or from metabolism. The cytoplasm and vacuole can buffer proton levels, but the main buffering activity is provided by the action of the ATPase. Saturation of the ATPase can lead to cell death thus metabolic activities are tightly coordinated with ATPase activity.

The weak organic acids such as acetic acid and formic acid both have positive and negative effects on the bioethanol produetion proeess. In fermentations using S. cerevisiae NCYC 2592, an addition of aeetie acid in a concentration of 20 mM increased the ethanol produetivity (unpublished data). The low acetic acid concentrations (lower than 20 mM) did not have an impact on the yeast viability. At fermentations with higher acid concentration, the intracellular pH decreases, requiring plasma membrane ATPase to pump protons out of the cell. The depletion of ATP affected the biomass formation. In comparison with acetic acid, formic acid has a more severe inhibitory effect, which has also been observed in other biosynthesis processes, e.g. succinic acid formation. ... 

Serrano R. Kielland-Brandt MC, Fink CR. Yeast plasma membrane ATPase is essential for growth and has homology with (Na + K ), K - andCa -Atpases. Nature 1986 319 689-693. 

Cyrklaff M, Auer M, Kuhlbrandt W, et al. 2-D structure of the Neurospora crassa plasma membrane ATPase as determined by electron cryomicroscopy. EMBOJ 1995 14 1854-1857. 

Harper JF, Manney L, Sussman MR (1994) The plasma membrane ATPase gene family in Arabidopsis Genomic sequence of AHA 10 which is expressed primarily in developing seeds. Mol Gen Genet 244 572-587... 

Auer M, Scarbrough GA, Kuhlbrandt W (1998) Three dimensional map of the plasma membrane ATPase in the open conformation. Nature 392 840-843... 

Figure 8. Solubilized plasma membrane ATPase activity in relation to source of initiation for lipid peroxidation. Adapted from Ref. 21.

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