| (a) Apo-CaM (no calcium), (b) the calcium-bound state, with four Ca2+ bound to each CaM molecule. The Ca2+-bound state has altered conformation and surface accessibility. (c) Ca2+–CaM bound to a peptide target. The altered surface of the Ca2+-bound state allows CaM to bind with increased affinity to specific peptide targets on the surface of proteins. Note that there are other targets that bind tightly to the apo-CaM state, but that are released in the Ca2+-bound state. ((a) PDB 1cfc, (b) PDB 3cln, (c) PDB 1cdl) |
