Calmodulin is a calcium-dependent protein that regulates the activity of a diverse array of enzymes, ion channels, and other proteins and thus has diverse roles in cell function. W-7 is a cell-permeable antagonist of calmodulin (Ki = 11 μM). Two molecules of W-7 bind to calcium-binding domains in each calmodulin molecule, blocking its interaction with target proteins. W-7 also associates, at lower affinities, with calcium-binding domains of other proteins, including troponin C and myosin light chain kinase (Ki = 70 and 300 μM, respectively).
