Active calcium transport in human red cells

Sarkadi, Balázs

doi:10.1016/0005-2736(80)90573-8

Cited by 90 publications

(29 citation statements)

References 179 publications

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“…31 ) Neutral Ca 2 + -ATPase was inhibited by lanthanide and vanadate, in agreement with the results for the erythrocyte calcium pump. 15,16,20) Although their effect was small in this experiment, it may imply that neutral Caz + -ATPase can be classified as a P type of ATPase. 20 ) The Ca 2 + -ATPase activity in the membrane fraction of human milk may represent an enzymatic basis for the calcium pump.…”

Section: Discussionmentioning

confidence: 69%

Enzymatic Properties of Two Calcium-stimulated ATPases in the Neutral and Acidic pH Regions Found in the Membrane Fraction of Human Milk

Kanno

Takeda

Cho

1992

Bioscience, Biotechnology, and Biochemistry

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Section: Discussionmentioning

confidence: 69%

Enzymatic Properties of Two Calcium-stimulated ATPases in the Neutral and Acidic pH Regions Found in the Membrane Fraction of Human Milk

Kanno

Takeda

Cho

1992

Bioscience, Biotechnology, and Biochemistry

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“…The calcium concentration needed for half-maximal binding of calmodulin to other proteins ranges from 2 to 11 PM free calcium 133-351. This should be compared with the estimated free calcium concentration in human erythrocytes of 0. l-l ,uM [36]. Thus the available calcium is perhaps not sufficient to activate calmodulin.…”

Section: Resultsmentioning

confidence: 99%

Calmodulin binding to human spectrin

Berglund¹,

Backman²,

Shanbhag³

1984

FEBS Letters

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Calmodulin is shown to interact with human spectrin dimer. The binding was highly calcium-dependent and observed in two different kinds of experiments. Firstly, affinity chromatography of calmodulin on a Sepharose 4B column with immobilized spectrin, and secondly, partition in aqueous two-phase polymer systems. In the column experiments stoichiometric amounts of calmodulin were retained on the spectrin-Sepharose column when micromolar concentrations of calcium were present. The calmodulin bound could be eluted with EGTA. The partition coefficient of c~modulin in an aqueous two-phase polymer system containing calcium was changed upon addition of spectrin, indicating an association between the two proteins. In the absence of calcium, spectrin did not cause any change in the partition behaviour of calmodulin, thus showing that the association requires calcium. Cdmodulin Human spectrin Protein-pratein interaction Aqueous two-phase partitionErythrocyte

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“…It has been proposed that there is a reversible shift between low-and high-affinity states of Ca2+-ATPase induced by the Ca2+-dependent binding of the low-molecular-weight cytoplasmic activator protein, calmodulin, to the erythrocyte membrane (Sarkadi, 1980). The method of ghost preparation in the absence of chelating agents that we have adopted, however, is known to yield only a high-affinity Ca2+-ATPase activity (Schatzmann, 1973).…”

Section: Discussionmentioning

confidence: 97%

“…It is therefore possible that the elevated Ca2+-ATPase activity that we have observed in ghost preparations from patients with DMD could be related to either changes in the response of the enzyme to calmodulin or alterations in the properties of calmodulin itself. As the method of ghost preparation that we have used will not yield calmodulin-free ghosts (Sarkadi, 1980), the elevated Ca2+-ATPase activity of ghost membranes from DMD patients could be due to differential retention of calmodulin in such preparations. Luthra et al (1979) have examined the effects of calmodulin on membrane Ca2+-ATPase in normal and DMD-patient erythrocytes.…”

Section: Discussionmentioning

confidence: 99%

“…In addition the progress curve for the enzyme was linear for at least 75min at 18 0C, implying that excess substrate was present at this temperature and that the measured v0 reflected true Vmax.I Several explanations can be put forward to explain discontinuities in Arrhenius plots (Dixon & Webb, 1979;Raison, 1973). The Ca2+-ATPase reaction is thought to involve more than one step subsequent to the formation of the enzyme-substrate complex (Sarkadi, 1980), and it is possible that these reactions have different temperature coefficients. Thus a discontinuity in Arrhenius plots can arise owing to a change in the rate-limiting step.…”

Section: Discussionmentioning

confidence: 99%

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Erythrocyte-ghost Ca2+-stimulated Mg2+-dependent adenosine triphosphatase in Duchenne muscular dystrophy

Dünn¹,

Burghes²,

Dubowitz³

1982

Biochemical Journal

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The Ca2+-stimulated Mg2+-dependent ATPase activities (Ca2+-ATPase) of erythrocyteghost membranes from patients with Duchenne muscular dystrophy (DMD) and carriers of DMD were compared with activities of normal controls. The Ca2+-ATPase activity of DMD-patient ghost preparations was found to follow the same pattern of activation by Ca2+ as the control membranes. However, the Ca2+-ATPase activity in DMD and some DMD-carrier preparations was substantially elevated compared with controls. To characterize further the elevated Ca2+-ATPase activity found in DMD-patient ghost membrane preparations, we estimated kinetic parameters using both fine adjustment and weighting methods to analyse our experimental data. It was established that in both DMD and DMD-carrier preparations the increase in Ca2+-ATPase activity was reflected by a significant increase in Vmax rather than by any change in Km. The response of the membrane Ca2+-ATPase activity to changes in temperature was also investigated. In all preparations a break in the Arrhenius plot occurred at 200C, and in DMD and DMD-carrier preparations an elevated Ca2+-ATPase activity was detected at all temperatures. Above 200C the activation energy for all types of preparation was the same, whereas below this temperature there appeared to be an elevated activation in DMD and DMD-carrier preparations compared with normal controls. The concept that a generalized alteration in the physicochemical nature of the membrane lipid domain may be responsible for the many abnormal membrane properties reported in DMD is discussed.Duchenne muscular dystrophy (DMD) is an

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Active calcium transport in human red cells

Cited by 90 publications

References 179 publications

Enzymatic Properties of Two Calcium-stimulated ATPases in the Neutral and Acidic pH Regions Found in the Membrane Fraction of Human Milk

Enzymatic Properties of Two Calcium-stimulated ATPases in the Neutral and Acidic pH Regions Found in the Membrane Fraction of Human Milk

Calmodulin binding to human spectrin

Erythrocyte-ghost Ca2+-stimulated Mg2+-dependent adenosine triphosphatase in Duchenne muscular dystrophy

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