Calcium-Activated Phosphate Uptake in Contracting Corn Mitochondria

Truelove, Bryan; Hanson, James A.

doi:10.1104/pp.41.6.1004

Cited by 27 publications

(29 citation statements)

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“…Calciuim releases the phosphate inhibition 1 (25). Dinitrophenol in low concentration (30 jM) uncouples the substrate-powered phosphate uptake but does not reduce respiration or the contraction process (25). From these observations we have concluded that the contraction process is very closely linked to electron transport, and that the level of contraction reflects the level of non-phosphorvlated high energy intermediate (23,25 (25).…”

mentioning

confidence: 70%

“…Substrate-powered calcium accumulation is dependent upon phosphate, and phosphate acctumulation is dependent tupon calcium, or the related strontium ion which is about half as effective (10,25). The mitochondria show no pronounced tuncotupling responses to Ca; the small decline in P /O ratio with 1 myN Ca is due to diversion of phosphate from ATP formation into Pi acctumtulation (7).…”

mentioning

confidence: 99%

“…The ATP-powered contraction is oligomycin sensitive and releases Pi, accounting for the bulk of the ATPase activity (23). The substrate powered contraction is very closely linked to respiration and is inhibited about 40 % by 1 mm phosphate (23,25). Calciuim releases the phosphate inhibition…”

mentioning

confidence: 99%

“…The substrate powered contraction is very closely linked to respiration and is inhibited about 40 % by 1 mm phosphate (23,25). Calciuim releases the phosphate inhibition 1 (25). Dinitrophenol in low concentration (30 jM) uncouples the substrate-powered phosphate uptake but does not reduce respiration or the contraction process (25).…”

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confidence: 99%

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Contracted State as an Energy Source for Ca Binding and Ca + Inorganic Phosphate Accumulation by Corn Mitochondria

Kenefick

Hanson

1966

Plant Physiol.

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Swnmary. An investigation has been made of the possibility of tutilizing the potential energy of the contracted state of corn mitochondria to drive Ca + inorganic phosphate accumulation. Contraction was obtained with succinate or NADH oxidation. In the succinate experiments the mitochondria were contracted in buffered KCl layered over sucrose in centrifuge tubes and centrifuged down through distinct wash, reactive and isotope exchange layers. In the NADH experiments, ion accumulation was initiated upon exhaustion of the substrate. The results show that mitochondria in the contracted state will actively bind some 45Ca, but no real accumtulation occurs until inorganic phosphate is available. Substrate powered contraction in the presence of inorganic phosphate also provides a potential for accumulation upon subsequent reaction of the mitochondria with Ca. It is deducted that contraction is due to X-I formation, to which Ca will bind. Subsequent reaction with inorganic phosphate produces CaX-P, which is the transport moiety. When X-P is formed first, Ca also reacts to produce CaX-P. Hence it is immaterial which ion reacts first with the contracted state. Contraction is believed to result from the action of a mechanoenzyme, presumably I-. The stability of CaX-I must be low for the mitochondria swell very rapidly tupon exhatustion of NADH or blocking of stuccinate oxidation by cyanide.Previotus papers from this laboratory have reported the characteristics of corn mitochondria in Ca + Pi accumulation and in swelling-contraction. Substrate-powered calcium accumulation is dependent upon phosphate, and phosphate acctumulation is dependent tupon calcium, or the related strontium ion which is about half as effective (10,25). The mitochondria show no pronounced tuncotupling responses to Ca; the small decline in P /O ratio with 1 myN Ca is due to diversion of phosphate from ATP formation into Pi acctumtulation (7).Swelling is spontaneous in buffered KCl, with rapid contraction not only with ATP and Mg btut also with the simple addition of an oxidizable substrate (23). The ATP-powered contraction is oligomycin sensitive and releases Pi, accounting for the bulk of the ATPase activity (23). The substrate powered contraction is very closely linked to respiration and is inhibited about 40 % by 1 mm phosphate (23,25). Calciuim releases the phosphate inhibition

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Contracted State as an Energy Source for Ca Binding and Ca + Inorganic Phosphate Accumulation by Corn Mitochondria

Kenefick

Hanson

1966

Plant Physiol.

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“…Its importance in the regulation of ion transport is well known (6,26). Its effects on the maintenance of RNA and of protein levels in Lemna have been described by Trewavas (24,25), and these components are considered central indices of senescence.…”

Section: Discussionmentioning

confidence: 99%

Deferral of Leaf Senescence with Calcium

Poovaiah¹,

Leopold²

1973

Plant Physiol.

169

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In view of the possibility that senescence may be a consequence of the deterioration of membrane compartments in the cells of leaves, calcium was studied as a possible agent which might defer senescence. The senescence of corn leaf discs was deferred by added calcium, and the effect was additive to the cytokinin deferral of senescence. Likewise, the senescence of Rumex leaf discs was deferred by added calcium, and the effect was additive to the gibberellin deferral of senescence.Detailed experiments with corn leaf discs established that the increase in apparent free space associated with senescence was completely prevented by calcium. An increase in hydraulic permeability during senescence was likewise demonstrated, and this increase was deferred by calcium; calcium plus benzyladenine was even more effective. Each of the measured functions of leaf senescence (chlorophyll content, protein decrease, apparent free space increase, and hydraulic permeability increase) was suppressed by calcium, and the interpretation is offered that the effects are a consequence of the calcium function in maintaining cellular membranes.Since the discovery by Richmond and Lang (17) growth chamber (2000 ft-c, 16 hr daily) at a temperature close to 22 C. At 8 to 10 days, leaf discs measuring 1 cm in size were taken from the primary leaf with the aid of a cork borer. The discs were floated in 10 ml of test solution, 10 discs per Petri dish in darkness at 25 C for 3 to 5 days.For the Rumex assay (Rumex obtusifolius L.), following the procedure of Whyte and Luckwill (27), old leaves which were uniformly green were selected from matured plants in the greenhouse, and they were allowed to stand overnight at 25 C in the dark with petiole in water. Leaf discs (1 cm) were cut with a cork borer and randomized, and 10 discs were floated in each Petri dish containing 10 ml of solution to be tested in the darkroom at 25 C for 4 or 5 days. Chlorophyll was extracted in ethanol. Ten leaf discs were transferred to 10 ml of ethanol in a closed vial and allowed to stand overnight, and absorbance was read at 665 nm. Experiments were repeated 4 to 6 times.For protein measurement 20 leaf discs were ground in a mortar and pestle with phosphate buffer at pH 6.5 and centrifuged at 800g to discard cellular debris. Protein was precipitated from the supernatant with 10% trichloroacetic acid and centrifuged at 10,000g for 10 min. The precipitate was dissolved in 5 ml of 0.1 N NaOH, and a 0.1-ml aliquot was used for protein analysis by the method of Lowry et al. (12).Apparent free space was determined by the method of Epstein (5). Twelve leaf discs were blotted on a paper towel to remove solution adhering to the surface. To initiate the absorption, the leaf discs were transferred to a salt solution (1 mm KCl) containing a radioactively labeled ion . At the end of the absorption period (90 min), the solution containing the radioactively labeled ion was decanted, and the leaf discs were blotted on a paper towel. Some leaf discs were used to determine the ini...

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Cellular Differentiation, Ageing and Ion Transport

Steveninck¹

1976

Transport in Plants II

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Calcium-Activated Phosphate Uptake in Contracting Corn Mitochondria

Cited by 27 publications

References 33 publications

Contracted State as an Energy Source for Ca Binding and Ca + Inorganic Phosphate Accumulation by Corn Mitochondria

Contracted State as an Energy Source for Ca Binding and Ca + Inorganic Phosphate Accumulation by Corn Mitochondria

Deferral of Leaf Senescence with Calcium

Cellular Differentiation, Ageing and Ion Transport

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