title: The interaction of tetraiodofluorescein with creatine kinase.
abstract: The dye 2',4',5',7'-tetraiodofluorescein is a potent inhibitor of creatine kinase (ATP:creatine N-phosphotransferase, EC 2.7.3.2) with an apparent competitive inhibition constant with respect to MgATP2- of 2.6 - 10(-5) M. The association of the dye with the enzyme elicited a red shift in the dye's spectrum, indicative of a binding site less polar than water. The dye binds to the enzyme with an equilibrium constant of dissociation of 1.7 - 10(-5) M. MgATP or MgADP competes for the dye-binding site. Creatine binds to creatine kinase-tetraiodofluorescein complex to form a ternary complex and further causes a blue-shift in the spectrum of the bound dye. The binding of the dye to fully active creatine kinase causes conformational change that was monitored by enzyme-bound 2-mercuri-4-nitrophenol, a conformation-dependent "reporter group".
mesh_terms: D001665:Binding Sites; D003401:Creatine / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism; D005452:Fluoresceins / Q000494:pharmacology; D007700:Kinetics; D011485:Protein Binding; D013053:Spectrophotometry
chemical_list: D005452:Fluoresceins; D003402:Creatine Kinase; D003401:Creatine