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Journal Article

Properties of the Sarcoplasmic ATPase Reconstituted by Oleate and Lysolecithin after Lipid Depletion

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The,  R.
Max Planck Institute for Medical Research, Max Planck Society;

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Hasselbach,  Wilhelm
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

The, R., & Hasselbach, W. (1972). Properties of the Sarcoplasmic ATPase Reconstituted by Oleate and Lysolecithin after Lipid Depletion. European Journal of Biochemistry, 28(3), 357-363. doi:10.1111/j.1432-1033.1972.tb01921.x.


Cite as: http://hdl.handle.net/11858/00-001M-0000-002D-894B-0
Abstract
1The ATPase activity of the sarcoplasmic membranes and the phosphoryl transfer reaction from ATP to the membranes depend on the composition of their lipid phase. 2Lipid depletion leads to a drastic (∼ 60%) reduction of phosphoprotein formation. Oleate raises and lysolecithin decreases phosphoprotein formation. In absence of calcium and/or magnesium neither the native nor the delipidated vesicular preparations are phosphorylated. 3The ATPase activity of lipid-depleted vesicular preparations reactivated by oleate or lysolecithin and that of the preparation containing the lipid hydrolysis products after phospholipase A treatment reaches half-maximal activation at concentrations of ionized calcium between 0.2 and 0.3 μM. The maximal ATP-splitting rates, however, differ considerably. 4Half-maximum activation by Mg · ATP for the oleate and lysolecithin-reactivated ATPase is reached at 10 μM and 100 μM, respectively. The corresponding Hill coefficients are 0.5 and 0.6. 5For the oleate-reactivated ATPase an activation energy of about 35 kcal/mol has been calculated which is similar to that of the extra ATPase of native vesicles. The activation energy of the lysolecithin-reactivated ATPase is about 8 kcal lower. 6The ATPase activity of the reconstituted vesicular preparations shows an identical steep decline at pH values >7. An irreversible damage of the vesicular preparations at higher values could be excluded. 7The properties of the reconstituted sarcoplasmic ATPase are discussed in relation to the sarcoplasmic calcium transport.