title: Fluorescence spectroscopic analysis of calpain II interactions with calcium and calmodulin antagonists.
abstract: 1. The intrinsic fluorescence of epoxysuccinyl-inhibited calpain II undergoes a Ca2(+)-dependent decrease which contrasts with the increase observed for calmodulin. 2. Calpain II was inhibited by the calmodulin antagonist toluidinylnaphthalenesulfonate (TNS), and a Ca2(+)-dependent increase in TNS fluorescence intensity was observed for epoxysuccinyl-inhibited calpain II. 3. The calmodulin antagonists calmidazolium CDZ and felodipine both caused decreases in the intrinsic fluorescence of epoxysuccinyl-inhibited calpain II. 4. Increasing concentrations of Ca2+ caused an increase in the fluorescence intensity of the inhibited enzyme in the presence of (CDZ), and a decrease in the presence of felodipine. 5. It is concluded from these studies that Ca2+ and calmodulin antagonists induce conformational changes in calpain II, and that changes occur in regions other than the Ca2(+)-binding domains.
authors.affiliation: Department of Chemistry, Ohio University, Athens 45701.
authors.forename: H
authors.initials: H
authors.lastname: Hong
authors.forename: S C
authors.initials: SC
authors.lastname: el-Saleh
authors.forename: P
authors.initials: P
authors.lastname: Johnson
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D015736:Felodipine / Q000494:pharmacology; D005456:Fluorescent Dyes; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008968:Molecular Conformation; D009282:Naphthalenesulfonates / Q000494:pharmacology; D013050:Spectrometry, Fluorescence
chemical_list: D002147:Calmodulin; D005456:Fluorescent Dyes; D007093:Imidazoles; D009282:Naphthalenesulfonates; C031938:calmidazolium; C009497:2-(4-toluidino)-6-naphthalenesulfonic acid; D002154:Calpain; D007930:Leucine; D015736:Felodipine; C024974:E 64; D002118:Calcium