Short Communication Human a Si-Casein Like Protein: Purification and N-Terminal Sequence Determination

Casein components of human milk are generally reported to belong to the β- and x-groups. In this research human casein fraction was obtained from pooled mature milk, either by ultracentrifugation or by acid precipitation. In both cases a minor component with a slightly higher mobility in SDS-PAGE than β-ca-sein was identified. The protein was purified to homogeneity, the N-terminal sequence of the first 14 amino acid residues of this new human casein subunit shows a high degree of homology with the a S1-casein seauences from other species.