title: Positions of the sites labeled by N-cyclohexyl-N'-(4-dimethylamino-1-naphthyl)carbodiimide on the (Ca2+ + Mg2+)-ATPase.
abstract: N-Cyclohexyl-N'-(4-dimethylamino-1-naphthyl)carbodiimide (NCD-4) labels (Ca2+ + Mg2+)-ATPase at Ca2+-protectable sites, believed to be at or near the two Ca2+ binding sites on the ATPase, and at nonspecific sites. The labeled ATPase has been reconstituted into lipid bilayers containing phosphatidylethanolamine labeled with fluorescein isothiocyanate. The distance between NCD-4 and fluorescein groups was measured using Forster energy transfer and the NCD-4 labels were found to be approx. 20 A from the lipid/water interface suggesting that the Ca2+ binding sites on the ATPase are also 20 A from the lipid/water interface. Addition of vanadate causes no change in the efficiency of energy transfer, suggesting that the Ca2+ binding sites on the E1 conformation of the ATPase do not move significantly with respect to the lipid/water interface in the E1-E2 transition.
authors.affiliation: Department of Biochemistry, University of Southampton, U.K.
authors.forename: F
authors.initials: F
authors.lastname: Munkonge
authors.forename: J M
authors.initials: JM
authors.lastname: East
authors.forename: A G
authors.initials: AG
authors.lastname: Lee
mesh_terms: D001665:Binding Sites; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002234:Carbodiimides; D004735:Energy Transfer; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000648:ultrastructure*; D010713:Phosphatidylcholines; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013050:Spectrometry, Fluorescence; D014639:Vanadium / Q000494:pharmacology
chemical_list: D002234:Carbodiimides; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D014639:Vanadium; C038088:N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; C017251:1,2-oleoylphosphatidylcholine