Effect of Temperature on the Plasma Membrane and Tonoplast ATPases of Barley Roots

DuPont, Frances M.

doi:10.1104/pp.89.4.1401

Cited by 26 publications

(22 citation statements)

References 33 publications

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“…The temperature optimum for ATP hydrolysis for maize root vanadate-sensitive proton pump was found above 40°C ( Figs. 1 and 2), which is similar to that reported previously (6,7,10,15,20). Therefore, proton transport and ATP hydrolysis by the maize root plasma membrane-type proton pump had different temperature optima.…”

Section: Discussionsupporting

confidence: 77%

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Effects of Temperature on the Coupled Activities of the Vanadate-Sensitive Proton Pump from Maize Root Microsomes

Bräuer

Loper²,

Schubert³

et al. 1991

Plant Physiol.

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The mechanism by which proton transport is coupled to ATP hydrolysis by vanadate-sensitive pumps is poorly understood. The effects of temperature on the activities of the vanadatesensitive ATPase from maize (Zea mays) roots were assessed to provide insight into the coupling mechanism. The initial rate of proton transport had a bell-shaped dependence on temperature with an optimal range between 20 and 300C. However, the rate of vanadate-sensitive ATP hydrolysis increased as the temperature was raised from 4 to 430C. The differential sensitivity of proton transport to temperatures above 300C was also observed when the ATPase was reconstituted into dioleoylphosphatidylcholine vesicles. Inhibition of proton transport with temperatures above 300C was associated with higher rates of proton leakage from the membranes. In addition, proton transport was more inhibited than ATP hydrolysis at temperatures below 100C. Reduced rates of proton transport at lower temperatures were not associated with higher rate of proton conductivity across the membranes. Therefore, the preferential inhibition of proton transport at temperatures below 100C may reflect an effect of temperature on the coupling between proton transport and ATP hydrolysis within the vanadate-sensitive ATPase.Plant cells contain two predominant classes ofproton translocating ATPase which energize solute transport (5,16 With vacuolar-type ATPase from maize (Zea mays) root tonoplast vesicles, the temperature dependence of the proton transport differed from that ofATP hydrolysis (17). The initial rate of proton transport declined as the temperature was increased above 25°C, whereas the rate of ATP hydrolysis by the pump continued to increase. These results supported the hypothesis that proton transport and ATP hydrolysis by the vacuolar ATPase were indirectly coupled. In this paper, the nature of the coupling mechanism of the plasma membranetype ATPase from maize root has been investigated in a similar manner by examining the temperature dependence of proton transport and ATP hydrolysis. MATERIALS AND METHODS Preparation of Membrane VesiclesMaize seedlings (Zea mays L., cv WF9 x Mo 17) were grown on filter paper moistened with CaCl2 (13). KI-washed microsomes were prepared from 3-d-old roots as described previously (3). The ATPase in these microsomes were reconstituted into di-18:1 PC' liposomes by a detergent dilution protocol using deoxycholate as described previously (3), using a lipid to protein ratio of 20 to 1 by weight. Protein concentration was determined by a modification of the Lowry method after precipitation by TCA in the presence of deoxycholate (2). Proton Transport and ATP Hydrolysis AssaysProton transport was followed primarily by changes in the absorbance of AO at 492.5 nm as described by de Michelis et al. (5). Assays were conducted with Beckman DU-702 spectrophotometer equipped with a thermoregulated cell holder attached to a circulating water bath. Temperature in a cuvette containing assay medium adjacent to the sample was monitored. Typi...

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Section: Discussionsupporting

confidence: 77%

“…m *RATP, is equal to the magnitude ofthe inhibitory processes, kp,. 6. In addition, the time course for the generation of the proton gradient can be reproduced by knowing two of the following three parameters: RH, A, and kp.…”

Section: Materials and Methods Preparation Of Membrane Vesiclesmentioning

confidence: 99%

Effects of Temperature on the Coupled Activities of the Vanadate-Sensitive Proton Pump from Maize Root Microsomes

Bräuer

Loper²,

Schubert³

et al. 1991

Plant Physiol.

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“…Microsomal membranes were prepared, separated on linear or discontinuous sucrose gradients, and fractions were collected as described previously (13)(14)(15). TN was collected from the 22/30% sucrose interface and PM was collected from the 34/40% sucrose interface.…”

Section: Membrane Preparationmentioning

confidence: 99%

“…It has been suggested that both types oftransporter may exist in a single membrane type (2, 30) although this has not been investigated in higher plants. We examined the Ca2+-transport activity of microsomes isolated from barley roots in order to determine which ofthe two types ofCa2+ transporters were associated with the major organelle fractions.The mechanisms by which Ca2+ is transported out of the cytoplasm against a large concentration gradient can be studied using isolated membrane vesicles (3,6,7,11,17,22,28,31,32 (13)(14)(15)(16). In the present paper the mechanisms and capacity for formation of Ca2`gradients by these vesicles are assessed.…”

mentioning

confidence: 99%

“…DuPont et al (15) demonstrated that membrane fractions enriched in ER, tonoplast or plasma membrane can be isolated from barley roots by sucrose density gradient centrifugation. The vesicles are sealed and properly oriented to allow generation of ApH by the PMand V-ATPases (13)(14)(15)(16). In the present paper the mechanisms and capacity for formation of Ca2`gradients by these vesicles are assessed.…”

mentioning

confidence: 99%

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Calcium and Proton Transport in Membrane Vesicles from Barley Roots

DuPont

Bush²,

Windle³

et al. 1990

Plant Physiol.

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(3,11,19,22,31,32) while the Ca2+-ATPases are associated with the ER and plasma membrane (6,7,9,11,17,28,31). It has been suggested that both types oftransporter may exist in a single membrane type (2, 30) although this has not been investigated in higher plants. We examined the Ca2+-transport activity of microsomes isolated from barley roots in order to determine which ofthe two types ofCa2+ transporters were associated with the major organelle fractions.The mechanisms by which Ca2+ is transported out of the cytoplasm against a large concentration gradient can be studied using isolated membrane vesicles (3,6,7,11,17,22,28,31,32 (13)(14)(15)(16). In the present paper the mechanisms and capacity for formation of Ca2`gradients by these vesicles are assessed. A prominent Ca2+/nH+ antiporter activity in tonoplast vesicles is characterized and evidence for a non-ER, non-plasma membrane Ca2+-ATPase is presented. A distinction is made between the activity of the Ca24/nH' antiporter and independent effects of Ca2+ on the formation and maintenance of ApH by the PM-and V-ATPases.Precise regulation ofcytoplasmic Ca2" may be an important element of signal transduction in plant cells (23,27), as it is in animal cells (12). Resting levels of cytoplasmic Ca2" are reported to be less than 0.5 AM in plants (8,18,26). These low levels ofcytoplasmic Ca2" are maintained by active uptake into organelles and export across the plasma membrane (7,12,26). To date, two types of Ca2" transport activity have been described in plant cells, one which is dependent on the MATERIALS AND METHODS Plant MaterialSeeds of barley (Hordeum vulgare L. cv CM72) were sown above an aerated solution containing full strength nutrients 2 Abbreviations: ApH, difference in pH across the vesicle membrane; ESR, electron spin resonance; PM-ATPase, plasma membrane H+-ATPase; PM, plasma membrane-enriched membrane fraction; 6,"5N,2,6,6, 1-'5N-1-oxyl; TN, tonoplast-enriched membrane fraction; Q, fluorescence quench; V-ATPase, vacuolar-type H+-ATPase; DCCD, dicyclohexylcarbodiimide; nH, number of H+ where n is unknown; BTP, bistris propane.

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A Quantitative Model for Using Acridine Orange as a Transmembrane pH Gradient Probe

Clerc¹,

Barenholz

1998

Analytical Biochemistry

103

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Effect of Temperature on the Plasma Membrane and Tonoplast ATPases of Barley Roots

Cited by 26 publications

References 33 publications

Effects of Temperature on the Coupled Activities of the Vanadate-Sensitive Proton Pump from Maize Root Microsomes

Effects of Temperature on the Coupled Activities of the Vanadate-Sensitive Proton Pump from Maize Root Microsomes

Calcium and Proton Transport in Membrane Vesicles from Barley Roots

A Quantitative Model for Using Acridine Orange as a Transmembrane pH Gradient Probe

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