Figure 5.

In vitro Motility assay for Troponin containing C-terminus deletion mutations in cTnI.

Enhancement of Ca²⁺-sensitivity of regulated thin filament sliding speed relative to WT control (filled circles and solid line) after removing 1 (open triangles and dotted line), 3 (open squares and long-dashed line) or 5 (open inverted triangles and short-dashed line) C-terminal residues from cTnI. In vitro motility assays were conducted and filament sliding speeds were quantified as described in Materials and Methods. Each point represents the mean ± SEM sliding speed for all filaments quantified in one flow cell, and each flow cell represents one of the four troponin constructs tested at one pCa. All speeds were normalized to nonlinear least squares regression s_max + s_min (in μm s⁻¹) for the same troponin. Lines represent nonlinear least squares regressions of the Hill Eq for normalized speed data, as described in Materials and Methods; see Table 2 for regression parameter estimates.