The Sequence of Sheep κ‐Casein: Primary Structure of <i>para</i>‐κ_A‐Casein

Abstract

The primary structure of sheep para‐x A ‐casein, the N‐terminal portion of x ‐casein, was established. The reduced alkylated protein was subjected to digestion with trypsin. The resulting soluble peptides were purified by a combination of Dowex 1 × 2 chromatography and electrophoresis and chromatography on paper; the core peptides were solubilized in 50% formic acid and filtered on Sephadex G‐50. The amino‐acid sequence of these peptides was determined chiefly with a Sequencer. Alignment of the tryptic peptides into a single chain containing 105 amino acids was determined from basic overlap peptides (tryptic core peptides with several basic amino acids; chymotryptic peptides). Some comparisons were achieved with cow para‐x A ‐Casein.