What question did this study set out to answer?

Determine the intracellular calcium affinity, maximum transport rate, and ATP-to-calcium stoichiometry of the active calcium pump in human red blood cells.

December 1, 1973The Journal of PhysiologyOpen Access

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

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HSH. J. SchatzmannUniversity of Bern

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Implication

Experimental study reveals a 1:1 calcium-to-ATP stoichiometry and high pump affinity in human red cells, suggesting intracellular calcium remains tightly suppressed under physiological conditions.

Key Points

Determine the intracellular calcium affinity, maximum transport rate, and ATP-to-calcium stoichiometry of the active calcium pump in human red blood cells.
Assayed calcium efflux using resealed human red cell ghosts loaded with Ca-EGTA buffer solutions across varying internal and external calcium concentrations (3 × 10⁻⁷ to 5 × 10⁻³ M).
Loaded red cells with up to 1 µmole Ca/ml cells using cold treatment with the mercurial PCMBS for 15 hours before washing and measuring calcium extrusion.
Measured the rate of ATP hydrolysis alongside calcium transport to assess the stoichiometric coupling ratio.
The intracellular free Ca²⁺ concentration for half saturation of the pump was ≤ 4 × 10⁻⁶ M, aligning with the Ca²⁺ + Mg²⁺-ATPase dissociation constant.
The maximal calcium transport rate reached 0.148 ± 0.009 µmole/ml cells·min at 28 °C and remained independent of external Ca²⁺ concentrations from 3 × 10⁻⁷ to 5 × 10⁻³ M.
Stoichiometric analysis indicated a 1:1 coupling ratio of calcium ions transported per ATP molecule hydrolysed rather than a 2:1 ratio.

Cite This Study

H. J. Schatzmann (1973) studied this question.

synapsesocial.com/papers/6a8bbcddf71fc1553cbea7b7 https://doi.org/10.1113/jphysiol.1973.sp010403

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Implication

Experimental study reveals a 1:1 calcium-to-ATP stoichiometry and high pump affinity in human red cells, suggesting intracellular calcium remains tightly suppressed under physiological conditions.

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

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Implication

Key Points

Cite This Study

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

Discussion

Member takes

Implication

Key Points

Cite This Study

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