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Calcium ion transport by pig erythrocyte membrane vesicles.

ABSTRACT: Preincubating pig erythrocyte membranes with ATP enhances their ability to accumulate Ca(2+) against a concentration gradient. The extent of this increase is dependent on preincubation time over the period 0-60min. As the accessibility of outside membrane markers is decreased by preincubation and as accumulated Ca(2+) is not removed by EGTA [ethanedioxybis(ethylamine)tetra-acetate], it is suggested that ATP causes the formation of sealed inside-out vesicles which can transport Ca(2+) inward. The transport system requires ATP and Mg(2+) and exhibits an apparent dissociation constant for Ca(2+) of approx. 100mum. Since the dissociation constant for Ca(2+)-sensitive ATPase (adenosine triphosphatase) in these preparations is similar, it is concluded that this ATPase is responsible for Ca(2+) transport. Polyphosphoinositide concentrations are also increased during incubation with ATP; however, there is no change in their rate of synthesis or breakdown during Ca(2+) transport.

SUBMITTER: Buckley JT

PROVIDER: S-EPMC1168316 | biostudies-other | 1974 Sep

REPOSITORIES: biostudies-other

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