Calcium-binding protein from human small intestine. Purification and characterization of a 10,000 molecular weight protein.

A calcium-binding protein (CaBP) was purified from human small intestinal mucosa by ammonium sulphate fractionation, gel filtration and chromatofocusing. Antibodies against CaBP were raised in rabbits and CaBP was then isolated from human intestinal cytosol by a one-step immunoadsorbent procedure. In polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate CaBP migrated as a single band corresponding to a molecular weight of 10,000. The calcium-binding ability of CaBP was demonstrated by increased electrophoretic mobility of CaBP in the presence of EDTA as demonstrated by immunoblotting of agarose gels. CaBP antibody showed no cross reaction with cytosolic proteins of duodenum from rat or pig. The present study suggests that molecular properties and distribution of human intestinal CaBP is comparable to those of intestinal CaBP detected in lower mammalian species.