The Isolation and Properties of Some Soluble Proteins From Wool VII. The Heterogeneity of the High Sulphur Proteins

Abstract

The heterogeneity of the S-carboxymethyl derivatives of high-sulphur proteins from Merino wool has been explored by means of moving boundary electrophoresis, ultracentrifugation, chromatography on DEAE-cellulose, and fractionation by use of solubility differences. Fractions isolated by chromatography and fractional precipitation have been analysed for their content of sulphur and amino acids. There are at least eight proteins present, which contain in common relatively large numbers of S-carboxymethyl cysteine, proline, serine, and threonine residues and small numbers of lysine, histidine, and aspartic acid residues. Apart from these similarities they show big differences in their overall amino acid content.The content of S-carboxymethyl cysteine nitrogen in the various components ranges from about 10·4 to 17·8% of total nitrogen and there is a linear relation between the content of this amino acid residue and the electrophoretic mobility at pH 4·5 of each protein component. There is also an increase in sedimentation coefficient with increasing sulphur content over the series.