FIG. 6.

The COOH-terminal mobile domain of cTnI is not required for cTn's superactivation of maximum Ca²⁺-activated cardiac thin filament sliding speed. Thin filaments were reconstituted with varying equimolar concentrations of cTm and either WT cTn (striped bar) or cTn (TnI K164Δ) (solid bar). Error bars represent SEM. *represents a statistically significant difference (P < 0.05) between mutant and wild type. Comparison of mean filament sliding speeds shows that both cTn (TnI K164Δ) and WT cTn, at all concentrations tested, superactivate actomyosin cycling significantly and similarly over that with unregulated (dashed line) F-actin.