Abstract
IN the sarcoplasmic reticulum (SR) of skeletal muscles ion transport involves an ATP driven calcium pump. The mechanism by which calcium ions are transported across the membrane is unknown. It is reasonable to assume, however, that some conformational changes in the transport protein are associated with this process. These changes might be more subtle than a complete rotation or translation of the protein1. The experiments described here have been designed to follow the modification of the protein conformation by measuring changes in strength of the protein's tryptophan fluorescence. We have observed transient changes of intensity induced by calcium ions and fluorescence fluctuations during one single pumping cycle of the enzyme. The kinetic pathway of the ATPase reaction which is linked to the ionic transport has been investigated previously by fast techniques, such as chemical quench-flow and fluorescence with calcium indicators2,3. We have attmpted to relate the conformational events observed to some steps of the proposed enzymatic schemes2–5.
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DUPONT, Y., LEIGH, J. Transient kinetics of sarcoplasmic reticulum Ca2++Mg2+ ATPase studied by fluorescence. Nature 273, 396–398 (1978). https://doi.org/10.1038/273396a0
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DOI: https://doi.org/10.1038/273396a0
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