The Calcium Pump of the Surface Membrane and of the Sarcoplasmic Reticulum

Schatzmann, H. J.

doi:10.1146/annurev.ph.51.030189.002353

Cited by 143 publications

(55 citation statements)

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“…Yet, there are other observations (1,6,8,9) that cannot be easily accommodated by a protomeric Na,KATPase in the membrane. The more prudent guess may be that there is a combination of protomer-and diprotomerbased properties in the membrane-bound Na+ pump and, perhaps, in other P-type transport ATPases (36,42).…”

Section: Discussionmentioning

confidence: 99%

Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Ward

Cavieres

1993

Proc. Natl. Acad. Sci. U.S.A.

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A prominent feature of the Na,K-ATPase reaction is an ATP dependence that suggests high-and lowaffinity ATP requirements during the enzymic cycle. As only one ATP-binding domain has been identified in the a subunit and none has been identified in the (3 subunit, it has seemed likely that the apparent negative cooperativity results from subunit interactions in an (aP32 diprotomer. To test this possibility, we have examined the behavior of solubilized ap3 protomers of Na,K-ATPase down to 50 nM [y32P]ATP. Active-enzyme analytical ultracentrifugation shows that the protomer is the active species and that no oligomerization occurs during turnover. However, we find that dual ATP effects can be clearly demonstrated and that nonhydrolyzable ATP analogs can stimulate the Na,K-ATPase activity of the soluble protomer. We conclude that the apparent negative cooperativity is inherent to the ap protomer and that this should explain some of the complexities found with membrane-bound Na,KATPase and, perhaps, other P-type cation pumps.The sodium pump or Na,K-ATPase is the integral membrane enzyme that mediates the active transport of Na+ and K+ in animal cells (1). The ATP dependence of the Na,K-ATPase activity and the Na-K exchange catalyzed by the enzyme show signs of apparent negative cooperativity. LineweaverBurk plots, for instance, present a downward break (2). The high-affinity component seems to reflect the requirement of the phosphorylation step and the low-affinity effect parallels a noncatalytic acceleration of the release of occluded K+. In fact, adenosine 5'-[f3,'y-imido]triphosphate (p[NH]ppA), a nonphosphorylating ATP analog, can stimulate the Na,KATPase activity ofthe membrane-bound sodium pump at low ATP (3).The enzyme consists of two subunits: the a or catalytic chain, which in pig kidney has a sequence-derived molecular weight of 112,235, and the /8 chain, a glycoprotein with a protein molecular weight of 34,958 (4). By using affinity probes, one ATP binding domain has been mapped so far in the a subunit (5) and most binding studies return not more than one ATP site per a/3 protomer (1, 6, 7). In contrast, there are a number of features (6,(8)(9)(10) that strongly suggest that the sodium pump in the membrane is an oligomer of a/3 protomers, with interactions among substrate sites. For instance, Scatchard isotherms for ATP binding to the purified membrane-bound pump are curvilinear (9) but become straight lines (10) upon enzyme solubilization to defined a/3 protomers (11, 12) with dodecyloctaethyleneglycol monoether (C12E8), a nonionic detergent. Some experiments have suggested that there should be dual ATP effects not only on the oligomers but also on the protomer (3) and apparently conflicted with the single-site binding results (10). We decided, therefore, to make a careful inspection of nucleotide effects on the soluble protomer during turnover.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordanc...

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Section: Discussionmentioning

confidence: 99%

Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Ward

Cavieres

1993

Proc. Natl. Acad. Sci. U.S.A.

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“…The extrusion was assumed to be linear, despite the fact that at least three independent mechanisms have been shown to participate, calcium transport into the SR, calcium transport through the surface membrane and the Na + -Ca 2 + exchange [17,18]. As it will be discussed later, the SR calcium pump is more important in the fast removal of calcium than the other two justifying our choice of linear extrusion.…”

Section: Calcium Fluxes Evoked By K + -Depolarisation and Caffeinementioning

confidence: 99%

Determination of depolarisation- and agonist-evoked calcium fluxes on skeletal muscle cells in primary culture

Szappanos

Cseri

Deli

et al. 2004

Journal of Biochemical and Biophysical Methods

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“…Membranes were isolated from the pmr1 pmc1 cnb1 mutant transformed with ECA1 to determine if the ECA1 polypeptide (ECA1p) could be phosphorylated as intermediates of the reaction cycle of Ca 2؉ -pumping ATPases. In the presence of [␥- 32 Calcium is not only an important intracellular signal for many stimuli-induced responses in eukaryotes (1), it is also essential for the functioning of the secretory system. A variety of signals can trigger the opening of Ca 2ϩ -specific channels on the plasma membrane and endomembranes, causing massive Ca 2ϩ influx and accumulation in the cytoplasm.…”

Section: ؉mentioning

confidence: 99%

ECA1 complements yeast mutants defective in Ca ²⁺ pumps and encodes an endoplasmic reticulum-type Ca ²⁺ -ATPase in Arabidopsis thaliana

Liang

Cunningham

Harper

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

142

123

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The Calcium Pump of the Surface Membrane and of the Sarcoplasmic Reticulum

Abstract: The molecular architectures of SMP and SRP differ, yet the functional analogies between CAM-associated SMP and SRP are numerous. Most of the divergences observed may have their root in different behavior during dephosphorylation (see Table 1).

Cited by 143 publications

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Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Determination of depolarisation- and agonist-evoked calcium fluxes on skeletal muscle cells in primary culture

ECA1 complements yeast mutants defective in Ca ²⁺ pumps and encodes an endoplasmic reticulum-type Ca ²⁺ -ATPase in Arabidopsis thaliana

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The Calcium Pump of the Surface Membrane and of the Sarcoplasmic Reticulum

Abstract: The molecular architectures of SMP and SRP differ, yet the functional analogies between CAM-associated SMP and SRP are numerous. Most of the divergences observed may have their root in different behavior during dephosphorylation (see Table 1).

Cited by 143 publications

References 0 publications

Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Solubilized alpha beta Na,K-ATPase remains protomeric during turnover yet shows apparent negative cooperativity toward ATP.

Determination of depolarisation- and agonist-evoked calcium fluxes on skeletal muscle cells in primary culture

ECA1 complements yeast mutants defective in Ca 2+ pumps and encodes an endoplasmic reticulum-type Ca 2+ -ATPase in Arabidopsis thaliana

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ECA1 complements yeast mutants defective in Ca ²⁺ pumps and encodes an endoplasmic reticulum-type Ca ²⁺ -ATPase in Arabidopsis thaliana