A fluorescence temperature-jump study on Ca2(+)-induced conformational changes in calmodulin.
Calmodulin has been shown to alter its conformation so as to interact with a number of target proteins upon Ca2+ binding. A Ca2(+)-binding study of calmodulin was performed by monitoring the fluorescence of intrinsic tyrosine residues and the probe 1-anilinonaphthalene-8-sulfonate (ANS). ANS fluorescence was shown to reflect Ca2+ binding to both high- and low-affinity sites. On the one hand, tyrosine fluorescence was sensitive only to the high-affinity Ca2+ binding. Temperature-jump investigation of the ternary complex of Ca2(+)-calmodulin-ANS in combination with monitoring of ANS fluorescence demonstrated the kinetic characteristics of the conformational change. The relaxation process was attributed to Ca2(+)-induced conformational change and the rate constants of this process were evaluated. On the basis of the rate constants of the conformational change, a rapid response of calmodulin in Ca2+ signaling is suggested.
Tsuruta
H
H
Department of Materials Science, Faculty of Science, Hiroshima University, Japan.
Sano
T
T
D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence / Q000379:methods; D013816:Thermodynamics
D002147:Calmodulin; D002118:Calcium