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Free keywords:
Organic Chemistry; Bioorganic Chemistry; Concentration Jump; Charge Translocation
Abstract:
The Ca ATPase of the sarcoplasmic reticulum (SR) translocates Ca from the cytoplasmic
space into the lumen of the SR using ATP hydrolysis as an energy source. The established
stochiometry is 2 Ca/ATP (Hasselbach, 1978). The electrical current related to the turnover
of this transport enzyme could be measured recently (Hartung et al., 1987) by adopting a
method introduced for the measurement of pump currents generated by the NaK ATPase
(Fendler et al., 1985). Vesicles derived from fragmented SR are adsorbed on one side of a
planar (black) lipid membrane, acting as a capacitive electrode. Ca transport by the Ca
ATPase is initiated by an ATP concentration jump which is achieved by the photolysis of
caged ATP (Kaplan et al., 1978).
