Cysteine Sequences of Rabbit Skeletal Tropomyosin

Abstract

Amino acid analyses of tropomyosin have shown three cysteine residues per mole (M.W. 70 000) of tropomyosin. The cysteine content was determined by cysteic acid determinations, incorporation of 14C-labelled iodoacetic acid into the protein, and the analysis of S-carboxymethylcysteine after acid hydrolysis. The isolation of three unique cysteinyl peptides is incompatible with a homogeneous tropomyosin preparation of two chemically identical subunits. The amino acid sequences reported in this study indicate a regular repeat of hydrophobic residues as required by the inter-chain packing of a coiled-coil structure.