Purification and characterization of a novel calcium-binding protein, S100C, from porcine heart

A novel Ca(2+)-binding protein, which we have named S100C (Ohta et al. (1991) FEBS Lett. 295, 93-96), was purified to homogeneity from porcine heart by Ca(2+)-dependent dye-affinity chromatography. S100C possesses some properties of S100 proteins, such as self-association and exposure of a hydrophobic site upon binding of Ca2+ but it differs from S100 proteins in forms of its isoelectric point (pI = 6.2), cross-reactivity with antibodies, staining by Stains-all, and its Ca(2+)-dependent interaction with the immobilized dye. S100C bound to cytoskeletal components at physiological concentrations of Ca2+. Moreover, it was found that 125I-labeled S100C interacted with annexin I in a Ca(2+)-dependent manner. S100C also inhibited the phosphorylation of annexin I by protein kinase C. These data suggest that S100C might act to regulate the cytoskeleton in a Ca(2+)-dependent manner via interactions with annexin I.