Differential Ion Stimulation of Plasmalemma Adenosine Triphosphatase from Leaf Epidermis and Mesophyll of Nicotiana rustica L

Abstract

An ATPase preparation, presumed to be associated with plasma membrane due to the coincidence on isopycnic gradients of ceUulase and ,8-glucan synthetase at high substrate, has been isolated from the epidermal and mesophyil of tobacco leaf. The ATPase from both tissues was found to prefer ATP over other nucleotides. The pH optimum was 7.0 in the presence of 3 millimolar MgCI2 and pH 6.5 in the presence of 3 millimolar MgCI2 and 100 milHimolar KCI. Monovalent ion stimulation patterns of the ATPases from these tissues were found to differ and ion accumulation patterns in these tissues reflect this difference: mesophyU accumulated roughly equal amounts of Na+ and Rb and its plasma membrane ATPase is also equaly stimulated by these ions; on the other hand, epidermal ATPase preparations showed a stronger stimulation by Rb+ than Na+ and this tissue was found to accumulate Rb' in preference to Na+. Abscisic acid and fusicoccin affected both ATPase activity and ion uptake, the former inhibiting and the latter stimulating these parameters. These data support the hypothesis that the epidermal plasmalemma ATPase is involved in stomatal opening.

Labeling and Isolation of Plasma Membranes from Corn Leaf Protoplasts

“…In addition, the position of these membranes on the sucrose density gradient agrees with the cell surface labeling study of Galbraith and Northcote (5). This confirms other work in establishing the position of plasma membranes in sucrose density gradients (9,10,(14)(15)(16).…”

“…In addition, the enzyme is substrate specific, showing a distinct preference for ATP over other substrates (unpublished data). This enzyme activity is characteristic of root and coleoptile plasma membranes (6,8,9,(13)(14)(15) and has also been detected in leaf tissue (16). While a K+-stimulated ATPase was readily detected, Table II indicates that this enzyme is best utilized as a qualitative marker rather than a quantitative marker.…”

“…Plasma membrane-enriched fractions have been isolated from numerous plant sources, including oat and corn roots (9,10,15), corn coleoptiles (7,12), green onion meristem (24), leek epidermal cells (2), sugarcane leaves (21), sugarcane cell suspensions (23), soybean suspension cultures (5), soybean roots (6), and tobacco epidermis (16). In most cases, the isolation method employed required mechanical disruption, usually grinding, followed by differential and density gradient centrifugation.…”

Phospholipid Requirement of the Vanadate-Sensitive ATPase from Maize Roots Evaluated by Two Methods

“…There are at least four possible ways that activity of the ATPase can be regulated: (a) gene regulation (30); (b) protein modification including phosphorylation (2); (c) allosteric like regulation by either plant hormones or other small molecules (17,25); and (d) alterations in the lipid environment surrounding the ATPase. Adaptation of plants to cold and the development of senescence have been associated with changes in fatty acid composition of membrane lipids and to a lesser extent types of polar lipids (3, 18) as well as changes in ATPase activity and maintenance of solute gradients (9,12,28).…”

Functional reconstitution of a proton-translocating system responsive to fusicoccin.

“…The nature of the step following FC binding-namely, the transduction mechanism of the signal to the cell machinery-is quite obscure. Circumstantial evidence suggests that the target molecule in higher plants is the plasma membrane H+-transporting ATPase (EC 3.6.1.34) (3), but attempts to demonstrate a substantial in vitro FC stimulation of this enzyme have yielded contradictory results (10)(11)(12)(13).…”