title: ACTA, a fluorescent analogue of thapsigargin, is a potent inhibitor and a conformational probe of skeletal muscle Ca2+-ATPase.
abstract: Thapsigargin is a highly potent and selective inhibitor of sarco-endoplasmic reticulum (SERCA) family of Ca2+-ATPases and a useful tool in research concerning the function of intracellular Ca2+ stores. We describe here a novel fluorescent derivative (8-O-(4-aminocinnamoyl)-8-O-debutanoylthapsigargin, termed ACTA) of this compound, acting as a Ca2+-ATPase inhibitor with a potency approaching that of thapsigargin. Binding of ACTA to the skeletal muscle sarcoplasmic reticulum vesicles results in a strong fluorescence enhancement, approximately 66% of which depends on ACTA association with Ca2+-ATPase. This specific component of ACTA fluorescence is sensitive to the E1-E2 conformational equilibrium of the pump. The combined properties of high potency and binding-dependent fluorescence suggest ACTA to be a useful probe for a range of studies involving the SERCA class of ATPases.
authors.affiliation: Department of Medical Physiology-Center for Cellular Communication, University of Copenhagen, The Panum Institute, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Procida
authors.forename: C
authors.initials: C
authors.lastname: Caspersen
authors.forename: H
authors.initials: H
authors.lastname: Kromann
authors.forename: S B
authors.initials: SB
authors.lastname: Christensen
authors.forename: M
authors.initials: M
authors.lastname: Treiman
mesh_terms: D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005456:Fluorescent Dyes; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology; D011487:Protein Conformation; D019284:Thapsigargin / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: C116112:8-O-(4-aminocinnamoyl)-8-O-debutanoylthapsigargin; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium