A SYNTHETIC PEPTIDE MIMICS TROPONIN-I FUNCTION IN THE CALCIUM-DEPENDENT REGULATION OF MUSCLE-CONTRACTION

A new technique for treating skinned cardiac muscle fibers has been de veloped in which troponin I is extracted, giving rise to unregulated f ibers. The effect of the 12-residue troponin I peptide on these fibers indicates that this region of troponin I is solely responsible for mu scle relaxation (inhibition of force). Furthermore, troponin I peptide -troponin C reconstituted fibers are stable through several contractio n-relaxation cycles indicating the peptide can switch binding sites be tween actin and troponin C. The troponin I peptide can substitute for the native protein as part of the calcium-sensitive molecular switch t hat controls muscle regulation.