Membrane proton ATPase

Her research interests originally focused on biological cell membranes, first working on phosphate transport in Escherichia coli and then the plasma membrane proton ATPase in Saccharomyces cerevisiae. While isolating vanadate-resistant mutants in yeast, she became fascinated with work showing that oral administration of vanadium salts alleviated symptoms of diabetes and switched her research focus to that area. She has pursued the insulin-enhancing mechanism of vanadium salts and complexes in cell culture, the STZ-induced diabetic rat, and human type 2 diabetic patients. The National Institutes of Health, the American Heart Association, and the American Diabetes Association have funded the work in her laboratory. Willsky has lectured all around the world and published both research articles and book chapters in this area. 

Figure 2.2), and can carry side chains which point outward from the membrane. In many cases the proteins are enzymes. Among these enzymes the intrinsic membrane proton ATPases deserve special attention as they pump H outward from the membrane and OH inwards (Briskin 1986), according to the scheme ... 

Fig. 2.2 Model of the proposed mechanism of SO/ transport throug a plant membrane by a high-affinity SO/ -H symporter (Smith 1999, enlarged). Transport is energized by a large integral membrane proton ATPase that pumps H to the outside of the membrane, and OH to the inside.

Fig. 3 A, B. The two mechanisms of xylose uptake by yeast A facilitated diffusion - the driving force is the concentration gradient between the medium and the cytosol - these transporters generally have a broad substrate range B proton-xylose symport. - the driving force is the proton motive force, which is maintained by the plasma membrane proton-ATPase. Adapted from [109]...

Boron also appears to be involved in redox metabolism in cell membranes. Boron deficiency was shown to inhibit membrane H -ATPase isolated from plant roots, and H -ATPase-associated proton secretion is decreased in boron-deficient cell cultures [71]. Other studies show an effect of boron on membrane electron transport reactions and the stimulation of plasma reduced nicotinamide adenine dinucleotide (NADH) oxidase upon addition of boron to cell cultures [72, 73]. NADH oxidase in plasma membrane is believed to play a role in the reduction of ascorbate free radical to ascorbate [74]. One theory proposes that, by stimulating NADH oxidase to keep ascorbate reduced at the cell wall-membrane interface, the presence of boron is important in... 

Ludwig,J., Kerscher, S., Brandt, U., Pfeiffer, K., Gedawi, F., Apps, D. K., and Schagger, H. (1998). Identification and characterization of a novel 9.2-kDa membrane sector-associated protein of vacuolar proton ATPase from chromaffin granules. J. Biol. Chem. 273, 10939-10947. 

Palmgren, M. G. (1998). Proton gradients and plant growth role of the plasma membrane H+-ATPase. Adv. Bot. Res. 28,1-70. 

The synthesis of the photoaffinity probe, NAZA-FL, lc, will be described elsewhere. The effects of this acyclic modifier on mitochondrial activities were assayed as previously described (5,6). The results are summarized in the Table. The effects, and the effective concentration range, of compounds lc and La are similar in the dark. With the photolabile modifier,< T(c, illumination with strong light resulted in an irreversible preferential inhibition of the energy-dependent proton movements this effect was not relieved by phosphatidylcholine vesicles. Hence, the modifier became covalently bonded in the vicinity of its implantation. Additional experiments were performed with phosphate-washed (12) membrane preparations (ATPase-enriched inner membrane frac-... 

A1 and concanamycin A—two established V-ATPase inhibitors.163 This observation was confirmed by both in vitro enzyme assays and in vivo activity studies in mutant yeast. These studies indicated that, while the benzolactone enamides were potent V-ATPase inhibitors, a profound selectivity occurred between the mammalian and fungal enzymes. Subsequent studies by De Brabander determined that salicylihalamide A binds irreversibly to the trans-membranous proton-translocating domain via A-acyliminium chemistry.164... 

The activated membrane-bound ATPase is functionally coupled to proton movements. Thus, a transmembrane pH gradient (acid inside) of a magnitude similar to that observed during light-induced coupled electron flow is developed during ATP hydrolysis. ATP hydrolysis is stimulated, while the coupled proton transport is inhibited, by the addition of uncouplers, indicating that the rate of ATP hydrolysis is also partially limited by the electrochemical gradient which it creates. Nevertheless, attempts to measure H /ATP ratios in this system yielded numbers much below the expected ratio of 3. 

The proton-ATPase complex, first purified by Pick and Racker [54], was reported to contain nine different subunits, four of which may belong to the membrane sector. Later studies in our laboratory detected only three subunits in the... 

Figure 6.3 (Right) Schematic depiction of anammox cell showing the anammoxozome and nucleoid. (Left) Postulated pathway of anaerobic ammonium oxidation coupled to the ana-mmoxosome membrane resulting in a proton motive force and ATP synthesis via membrane-bound ATPases. HH, hydrazine hydrolase HZO, hydrazine oxidizing enzyme NIR, nitrite reductase. (Redrawn from van Niftrik etal., 2004 and Kuypers et al., 2006).

Once the chromaffin granule is formed, low molecular components such as catecholamines, ATP and Ca are concentrated in the cisterna using the proton motive force provided by a proton ATPase [39,45]. Upon receiving stimulus, the granules fuse with the plasma membrane and the catecholamines are released from the cell. To prevent continual growth of the plasma membrane, portions of it must... 

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