Diversity of conformational states and changes within the EF-hand protein superfamily. Proteins: Struct. Funct. Genet. 37, 499–507. Edited by

ABSTRACT The EF-hand motif, which assumes a helix-loop-helix structure normally responsible for Ca21 binding, is found in a large number of functionally diverse Ca21 binding proteins collec-tively known as the EF-hand protein superfamily. In many superfamily members, Ca21 binding induces a conformational change in the EF-hand motif, lead-ing to the activation or inactivation of target pro-teins. In calmodulin and troponin C, this is de-scribed as a change from the closed conformational state in the absence of Ca21 to the open conforma-tional state in its presence. It is now clear from structures of other EF-hand proteins that this ‘‘closed-to-open’ ’ conformational transition is not the sole model for EF-hand protein structural re-sponse to Ca21. More complex modes of conforma-tional change are observed in EF-hand proteins that interact with a covalently attached acyl group (e.g., recoverin) and in those that dimerize (e.g., S100B, calpain). In fact, EF-hand proteins display a multi-tude of unique conformational states, together con-stituting a conformational continuum. Using a quan-titative 3D approach termed vector geometry mapping (VGM), we discuss this tertiary structural diversity of EF-hand proteins and its correlation with target recognition. Proteins 1999;37:499–507. r 1999 Wiley-Liss, Inc. Key words: calcium signaling; EF-hand protein; con-formational chang