title: The inhibitors thapsigargin and 2,5-di(tert-butyl)-1,4-benzohydroquinone favour the E2 form of the Ca2+,Mg(2+)-ATPase.
abstract: 2,5-Di(tert-butyl)-1,4-benzohydroquinone has been shown to inhibit the Ca2+,M(2+)-ATPase of sarcoplasmic reticulum with an affinity of 0.4 microM. It has been shown to shift the E2-E1 equilibrium for the ATPase towards E2, as shown previously for the inhibitor thapsigargin. The shift towards E2 results in a decrease in affinity for Ca2+, as also observed for thapsigargin. A marked decrease in the rate of the E2-E1 transition is observed for both BHQ and thapsigargin. A decrease in the equilibrium level of phosphorylation by Pi and of the steady-state level of phosphorylation by ATP are consistent with a decrease in the equilibrium constant for phosphorylation by Pi and an increase in the rate of dephosphorylation.
authors.affiliation: Department of Biochemistry, University of Southampton, UK.
authors.forename: M
authors.initials: M
authors.lastname: Wictome
authors.forename: F
authors.initials: F
authors.lastname: Michelangeli
authors.forename: A G
authors.initials: AG
authors.lastname: Lee
authors.forename: J M
authors.initials: JM
authors.lastname: East
mesh_terms: D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006873:Hydroquinones / Q000494:pharmacology*; D007700:Kinetics; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013050:Spectrometry, Fluorescence; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin; D014638:Vanadates / Q000494:pharmacology
chemical_list: D006873:Hydroquinones; D013729:Terpenes; C019359:2,5-di-tert-butylhydroquinone; D014638:Vanadates; D019284:Thapsigargin; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium