Structural Relation of Two S-100 Proteins in Bovine Brain; Subunit Composition of S-100 a Protein

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Abstract
Dodecyl sulfate/urea/polyacrylamide gel electrophoresis of S-100a protein, one of the two major components of the brain-specific S-100 protein, indicated the presence of two different subunits in the protein. These subunits (α and β subunits) were purified from the aminoethylated protein by column chromatography on Sephadex G-75, and the purified subunits were subjected to analyses. The results have shown that S-100a protein is a dimer of α and β subunits, with each subunit having a molecular weight of approximately 10500. Structural comparison of these subunits with the subunit of S-100b protein, the other component of S-100 protein consisting of two identical subunits with known amino acid sequence, has revealed that the β subunit and the subunit of S-100b protein are identical, so that S-100a protein is related to S-100b protein by sharing one of the subunits as a common structural constituent.