Figure 6

The open state of Ca²⁺-bound calmodulin [PDB:1CLL] is a result of a conformational change from calcium-free calmodulin ([PDB:1CFD], shown faded). The two "ends" of the "dumbbell" rotate relative to each other about the "handle" (central alpha helix); the computed axis of motion (blue) of the moving cluster (green) relative to the pinned cluster (red) is consistent with this motion.