Tropomyosin bound mainly to troponin T1 (residues 1-158) and the C-terminal region (243-259), while troponin I bound to residues 223-227, and troponin C binding was Ca2+-dependent.
The binding of the chymotryptic troponin T subfragments to tropomyosin, troponin I, and troponin C was semiquantitatively examined by using affinity chromatography, and also by co-sedimentation with F-actin and polyacrylamide gel electrophoresis in 14 mM Tris/90 mM glycine. Circular dichroism spectra of the subfragments were measured to confirm that the subfragments retained their conformational structures. Based on these results, the binding sites of tropomyosin, troponin I, and troponin C on the troponin T sequence were elucidated. Tropomyosin bound mainly to the region of troponin T1 (residues 1-158) with the same binding strength as to the original troponin T. The C-terminal region of troponin T (residues 243-259) was the second binding site to tropomyosin under physiological conditions. The binding site of troponin I was concluded to be the region including residues 223-227. The binding of troponin C was dependent on Ca2+ ion concentration. The C-terminal region of troponin T2 (residues 159-259) was indicated to be the Ca2+-independent troponin C-binding site and the N-terminal side of troponin T2 to be the Ca2+-dependent site.
Tanokura et al. (Tue,) reported a other. Chymotryptic subfragments of troponin T was evaluated on Binding sites of tropomyosin, troponin I, and troponin C on the troponin T sequence. Tropomyosin bound mainly to troponin T1 (residues 1-158) and the C-terminal region (243-259), while troponin I bound to residues 223-227, and troponin C binding was Ca2+-dependent.
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