CA2-PROTEINS( SIGNALING AND INTRACELLULAR CA2+ BINDING)

Changes in cytosolic Ca2+ concentrations evoke a wide range of cellula r responses and intracellular Ca2+-binding proteins are the key molecu les to transduce Ca2+ signaling via enzymatic reactions or modulation of protein/protein interations (Fig. 1), The EF hand proteins, like ca lmodulin and S100 proteins, are considered to exert Ca2+-dependent act ions in the nucleus or the cytoplasm. The Ca2+/phospholipid binding pr oteins are classified into two groups, the annexins and the C2 region proteins. These proteins, distributed mainly in the cytoplasm, translo cate to the plasma membrane in response to an increase in cytosolic Ca 2+ and function in the vicinity of the membrane. Ca2+ storage proteins in the endoplasmic or sarcoplasmic reticulum provide the high Ca2+ ca pacity of the Ca2+ store sites, which regulate intracellular Ca2+ dist ribution. The variety and complexity of Ca2+ signaling result from the cooperative actions of specific Ca2+-binding proteins. This review de scribes biochemical properties of intracellular Ca2+-binding proteins and their proposed roles in mediating Ca2+ signaling.