Calcium binding proteins are a class of proteins that bind free calcium ions within the cell. One particular type of highly characterized calcium binding proteins is the EF-hand calcium binding proteins. There are more than 250 EF-hand proteins, and they all share a common structural motif, a Ca2+-binding loop between two a-helices oriented perpendicular to each other. The term comes from a description of the C-terminal E-helix-loop-F-helix Ca2+-binding site in parvalbumin.
