Calcium Transport in Tonoplast and Endoplasmic Reticulum Vesicles Isolated from Cultured Carrot Cells

Bush, Daniel R.; Sze, Heven

doi:10.1104/pp.80.2.549

Cited by 106 publications

(95 citation statements)

References 28 publications

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“…13) and possesses proteins that facilitate transport of calcium across the tonoplast (3,5,11,23,24). Cytosolic levels of calcium are tightly controlled through homeostatic mechanisms (9,13).…”

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confidence: 99%

Characterization of Vacuolar Calcium-Binding Proteins

Randall

1992

Plant Physiol.

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The vacuole plays a major structural and biochemical role in the higher plant cell. Among the most studied properties of the vacuole have been transport activities. One important aspect of vacuolar function is its participation in the regulation of cytosolic calcium levels. To identify the molecular entities involved in calcium regulation, a study of vacuole-associated, calcium-binding proteins (CaBs) was initiated. A competition assay was used, and it was observed that the majority of the total cellular membrane-associated, calcium-binding activity resided in low-density fractions enriched in vacuole membranes. Much of that calcium-binding activity was inactivated by a 0.5 M KI wash, and of the remaining activity, 77% was estimated to be peripherally associated with vacuolar membranes, whereas 23% was integrally associated with the vacuolar membrane. Calcium-ligand blots were used, and four major CaBs, with apparent molecular masses of 64, 58, 55, and 42 kD, were detected in purified vacuole membrane fractions. Two of these, the 58-and the 55-kD polypeptide, also appear to be present in significant amounts in endoplasmic reticulum-enriched fractions. However, the 64-and the 42-kD polypeptide are found primarily in vacuolar fractions. It is interesting that expression of the 42-kD polypeptide appears to be restricted to the heavily vacuolated cortical tissues (i.e. it is not found in vascular tissues). The localization of CaBs in the vacuole is consistent with the presence of calcium uptake (H'/Ca2' antiport) and releaseinechanisms (inositol trisphosphate sensitive) on vacuolar membranes. These vacuoleassociated CaBs, which may play a role in calcium buffering, together with the calcium transport systems, could mediate the vacuolar component of cellular calcium homeostasis.

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confidence: 99%

Characterization of Vacuolar Calcium-Binding Proteins

Randall

1992

Plant Physiol.

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“…lB), suggesting an enrichment of this pump type in vacuolar membranes and PMs. Although the vacuolar HC-ATPase also utilizes GTP as a substrate, activity from the vacuolar H+ /Ca2' antiport was relatively low in the endomembrane vesicles from carrots (Bush and Sze, 1986). Furthermore, bafilomycin had little or no effect on Ca2+ pumping (data not shown).…”

Section: Ctp-driven Caz+ Transport 1s Cam-stimulatedmentioning

confidence: 95%

“…These cells are actively proliferating during the exponential growth phase and are highly secretory. Low-density membrane vesicles isolated from carrot suspension-cultured cells were abundant in vanadatesensitive Ca2+ pump activity (Bush and Sze, 1986). The transport activity was stimulated 2-to 3-fold by CaM and co-migrated with an ER marker on Suc gradients (Hsieh et al, 1991).…”

mentioning

confidence: 92%

“…3, A and B). Oxalate stimulation of Ca 2+ uptake is thought to be caused by formation of Ca 2+ -oxalate precipitate inside the vesicles, thus decreasing the magnitude of the Ca 2 " 1 " chemical gradient (Bush and Sze, 1986). If so, the stimulation of Ca 2+ uptake by oxalate would depend on an oxalate carrier that co-localized to the same compartment membrane as the Ca 2+ pump.…”

Section: Atp-dependent and Gtp-driven Ca2+ Transport Represents Two Smentioning

confidence: 99%

“…These energy-dependent Ca2+ transporters extrude cytosolic Ca2+ to the externa1 medium or into interna1 stores, such as the vacuole and the ER, and thus maintain low cytosolic [Ca"]. Because the affinity for Ca2+ of CaZf-ATPases is higher than that of the antiporter (Bush and Sze, 1986;Bush, 1995), the Ca2+ pumps are thought to play the major role in fine-tuning intracellular [Ca2+].…”

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confidence: 99%

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Distinction between Endoplasmic Reticulum-Type and Plasma Membrane-Type Ca2+ Pumps (Partial Purification of a 120-Kilodalton Ca2+-ATPase from Endomembranes)

1997

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Two biochemical types of Ca2+-pumping ATPases were distinguished in membranes that were isolated from carrot (Daucus carota) suspension-cultured cells. One type hydrolyzed GTP nearly as well as ATP, was stimulated by calmodulin, and was resistant to cyclopiazonic acid. This plasma membrane (PM)-type pump was associated with PMs and endomembranes, including vacuolar membranes and the endoplasmic reticulum (ER). Another pump (“ER-type”) that was associated mainly with the ER hydrolyzed ATP preferentially, was insensitive to calmodulin, and was inhibited partially by cyclopiazonic acid, a blocker of the animal sarcoplasmic/ER Ca2+ pump. Oxalate stimulation of Ca2+ accumulation by ER-type, but not PM-type, pump(s) indicated a separation of the two types on distinct compartments. An endomembrane 120-kD Ca2+ pump was partially purified by calmodulin-affinity chromatography. The purified polypeptide bound calmodulin reacted with antibodies to a calmodulin-stimulated Ca2+ pump from cauliflower and displayed [32P]phosphoenzyme properties that are characteristic of PM-type Ca2+ pumps. The purified ATPase corresponded to a phosphoenzyme and a 120-kD calmodulin-binding protein on endomembranes. Another PM-type pump was suggested by a 127-kD PM-associated protein that bound calmodulin. Thus, both ER- and PM-type Ca2+ pumps coexist in most plant tissues, and each type can be distinguished from another by a set of traits, even in partially purified membranes.

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Bibliography

2014

Intracellular Calcium

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Calcium Transport in Tonoplast and Endoplasmic Reticulum Vesicles Isolated from Cultured Carrot Cells

Abstract: Two active calcium (Ca2l) transport systems have been identified and

Cited by 106 publications

References 28 publications

Characterization of Vacuolar Calcium-Binding Proteins

Characterization of Vacuolar Calcium-Binding Proteins

Distinction between Endoplasmic Reticulum-Type and Plasma Membrane-Type Ca2+ Pumps (Partial Purification of a 120-Kilodalton Ca2+-ATPase from Endomembranes)

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