title: Calmodulin antagonists enhance calcium binding to calmodulin.
abstract: The effects of calmodulin (CaM) antagonists, N-(6-aminohexyl)(-5-chloro-1-naphthalenesulfonamide (W-7) and its derivatives or trifluoperazine (TFP) on the Ca2+ binding to CaM were investigated. In the presence of these CaM antagonists, the extent of the Ca2+ binding to CaM increased. Stoichiometrical Examination showed that these CaM antagonists dose-dependently increased the sensitivity of all four Ca2+ binding sites on CaM. An analysis of CaM by UV spectroscopy revealed that the conformation of the Ca2+ CaM complex in the presence and absence of these CaM antagonists differed. Therefore, binding of this CaM antagonist to CaM increase the binding of Ca2+ to this protein.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002417:Cattle; D066298:In Vitro Techniques; D011487:Protein Conformation / Q000187:drug effects; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000494:pharmacology*; D014268:Trifluoperazine / Q000494:pharmacology*
chemical_list: D002147:Calmodulin; D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D002118:Calcium