This basic science study demonstrates that the catalytic cycle of the sarcoplasmic reticulum calcium ATPase does not involve a major conformational rearrangement.
Does not inform clinical calcium modulation in heart failure; leaves open refined SERCA catalytic models without major rearrangement.
Fourier transform infrared spectroscopy was used to study ligand binding and conformational changes in the Ca2(+)-ATPase of sarcoplasmic reticulum. Novel in infrared difference spectroscopy, the catalytic cycle in the IR sample was started by photolytic release of ATP from an inactive, photolabile ATP-derivative (caged ATP). Small, but characteristic infrared absorbance changes were observed upon ATP release. On the basis of model spectra, the absorbance changes corresponding to the trigger and substrate reactions, i.e. to photolysis of caged ATP and hydrolysis of ATP, were separated from the absorbance changes due to the active ATPase reflecting formation of the phosphorylated Ca2E1P enzyme form. A major rearrangement of ATPase conformation as the result of catalysis can be excluded.
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Barth et al. (1990) studied this question.
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