Ca2+ binding to calmodulin in the pCa range 5.5-7.0 exposes hydrophobic sites that bind hydrophobic inhibitory ligands, including calmodulin antagonists, some Ca2+-antagonists and calmodulin-binding proteins. The binding of these hydrophobic ligands to calmodulin can be followed by the approx. 80% fluorescence increase they produce in dansylated (5-dimethylaminonaphthalene-1-sulphonylated) calmodulin (CDRDANS). In the presence of Ca2+, calmodulin binds the calmodulin inhibitor, R24571, with an affinity of approx. 2-3 nM and hydrophobic ligands, including trifluoperazine (TFP), W-7 [N-(6-aminohexyl)-5-chloronaphthalene-1-sulphonamide], fendiline, felodipine and prenylamine, with affinities in the micromolar range. This binding is strongly Ca2+-dependent and Mg2+-independent. Calmodulin shows a reasonably high degree of specificity in its binding of these ligands over other ligands tested. CDRDANS, therefore, provides a convenient and simple means of monitoring the interaction of a variety of hydrophobic ligands with the Ca2+-dependent regulatory protein, calmodulin. CDRDANS binds to phospholipid vesicles made of (dimyristoyl)phosphatidylcholine (DMPC) or (dipalmitoyl)phosphatidylcholine (DPPC) and produces fluorescence increases only in the presence of Ca2+ and at temperatures above their gel-to-liquid crystalline phase transition. Although the fluorescence changes in CDRDANS accurately report phase transitions in these liposomes, its binding to these vesicles is weak. Calmodulin probably requires a high-affinity lipid-bound receptor protein for its high-affinity binding to natural membranes.
Skip Nav Destination
Close
Article navigation
May 1983
- Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkAdvertising
Research Article|
May 01 1983
A fluorescent calmodulin that reports the binding of hydrophobic inhibitory ligands
Biochem J (1983) 211 (2): 473–479.
Citation
J D Johnson, L A Wittenauer; A fluorescent calmodulin that reports the binding of hydrophobic inhibitory ligands. Biochem J 1 May 1983; 211 (2): 473–479. doi: https://doi.org/10.1042/bj2110473
Download citation file:
Close
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Biochemical Society Member Sign in
Sign InSign in via your Institution
Sign in via your InstitutionGet Access To This Article
Cited By
Related Articles
An increase in cytosolic Ca2+ delays cAMP oscillations in Dictyostelium cells
Biochem J (October,1996)
Function of different proportions of apolipoprotein A-I cysteine mutants and apolipoprotein A-V on recombinant high-density lipoproteins in vitro
Biosci Rep (May,2019)