Figure 6.21     Schematic diagram of the conformational changes of calmodulin upon peptide binding. (a) In the free form the calmodulin molecule is dumbbell-shaped comprising two domains (red and green), each having two EF hands with bound calcium (yellow). (b) In the form with bound peptides (blue) the a helix linker has been broken, the two ends of the molecule are close together and they form a compact globular complex. The internal structure of each domain is essentially unchanged. The bound peptide binds as an a helix.