Structures of EF-hand Ca2+-binding proteins: Diversity in the organization, packing and response to Ca2+ binding

The growing database of three-dimensional structures of EF-hand calcium-bin ding proteins is revealing a previously unrecognized variability in the cof ormations and organizations of EF-hand binding motifs. The structures of tw elve different EF-hand proteins for which coordinates are publicly availabl e are discussed and related to their respective biological and biophysical properties. The classical picture of calcium sensors and calcium signal mod ulators is presented, along,vith variants on the basic theme and new struct ural paradigms.