PURIFICATION AND CHARACTERIZATION OF A NOVEL CALCIUM-BINDING PROTEIN,S100C, FROM PORCINE HEART

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