A rapid and simple method for the isolation of S100a(0) (??) protein by high-performance liquid chromatography

A rapid and simple method to isolate S100a(0) protein from the mixture of bovine S100 protein (S100a(0), S100a and S100b) is described. The S100 mixture purified from bovine brain was applied to an anion-exchange column, equilibrated with 50 mM Tris HC1 buffer (pH 8.0) in a high-performance liquid chromatography (HPLC) system. S100a(0), S100a and S100b proteins could be eluted separately from the column, which were identified by the immunoassay method, by the Tris-HC1 buffer containing a linear concentration gradient (0.25-0.4) M of NaCl. Immunoreactive S100a(0) protein was found in two peak fractions, and each S100a(0) fraction could be isolated (S100a(0)-1 and S100a(0)-2). Both fractions of S100a(0) protein showed a single band at the same position on acrylamide gel electrophoresis, and eluted in a single peak in the same fractions upon gel-filtration column chromatography. There was no significant difference in the amino acid composition between the two S100a(0) fractions. Since the S100a(0)-1 fraction aged for several months at 4 degrees C in the presence of 0.1% NaN(3) was found to contain four protein peaks including the fraction corresponding to the S100a(0)-2 fraction, the difference between the two S100a(0) fractions is probably due to some modification of amino acid residues in the molecule, which may occur both in vivo and in vitro.