Chymotryptic Subfragments of Troponin T from Rabbit Skeletal Muscle. I. Determination of the Primary Structure1

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Abstract
Chymotryptic subfragments from rabbit skeletal troponin T were purified using column chromatography. Molecular weight values on SDS gel electrophoresis, tryptophan contents, N- and C-terminal residues, and amino acid compositions were examined for each subfragment. Based on these findings, the positions of the subfragments in the sequence of troponin T were determined as follows: N-terminal acetylserine-l-tyrosine-158 for troponin T1 (MW 18,700); serine-156—C-terminal lysine-259 for troponin T2α3 (MW 12,200); leucine-159—C-terminal lysine-259 for troponin T2 (or troponin T2α) (MW 11,900); leucine-159—phenylalanine-242 for troponin T2βI (MW 10,200); leucine-159—tyrosine-227 for troponin T2βII (MW 8,400); leucine-159-leucine-222 for troponin T2βIII (MW 7,700); and serine-243—C-terminal lysine-259 for troponin T2γ (MW 1,800). The pathway of chymotryptic digestion of troponin T was also investigated and the results are discussed in relation to the higher structure of troponin T. The interaction of some chymotryptic subfragments with tropomyosin was also investigated by affinity chromatography.