The Isolation and Properties of a Tyrosine‐Rich Protein from Wool: Component 0.62

An apparently homogeneous protein (component 0.62), of mol. wt 6900, has been isolated from reduced and carboxymethylated wool proteins by chromatography on QAE-cellulose at pH 10.5, followed by chromatography on DEAE-cellulose at pH 8.26% of the amino acid residues of this protein are glycine, another 31% are aromatic amino acids, these together with serine account for 70% of the molecule. The component is unusual in containing no lysine, histidine, glutamic acid, methionine or isoleucine. Electrophoresis in starch gels at pH 8.6 and pH 2.4 and isoelectric focusing in polyacrylamide, indicate that the preparation contains a single component with an isoelectric point of 3.6. Chromatography on calibrated columns of Sephadex G-75 and Biogel P-10 gives single symmetrical peaks corresponding in elution volume with an apparent molecular weight of about 4700, whereas ultracentrifugation and sequence give a value close to 7000. It is probable that this discrepancy is due to an extreme retardation of the protein on Sephadex or Biogel due to the large number of aromatic amino acid residues present in the protein. Component 0.62 is almost completely insoluble below pH 9 but increases in solubility with increasing pH and is soluble to the extent of about 0.20% at pH 10.0. This protein component constitutes about 30% of the high-tyrosine type I protein group and accounts for at least 2% of the mass of fine Merino wools.