PRIMARY STRUCTURES OF CYSTEINE-CONTAINING PEPTIDES FROM CALCIUM ION-TRANSPORTING ADENOSINE-TRIPHOSPHATASE OF RABBIT SARCOPLASMIC-RETICULUM

A preliminary investigation of the primary structure of the Ca2+-transporting ATPase protein of rabbit skeletal-muscle sarcoplasmic reticulum is reported. The preparation of derivatives of delipidated protein in a form suitable for sequence analysis is described. Tryptic peptides containing S-carboxymethylcysteine residues were isolated from the reduced carboxymethylated protein, and their sequences were partially determined. The results are consistent with MW about 105,000 for the polypeptide, and the absence of extended repeated lengths of sequence. The distribution of tryptophan and cysteine residues between large, aggregated peptides and soluble tryptic peptides shows that these residues are concentrated in different regions of the primary structure. This observation agrees with other evidence that these residues are, on the whole, widely separated in the native protein.