Figure 5.
Myofibrillar ATPase at low [Ca2+] is much greater for reconstituted myofibrils containing D137L (light gray square) and D137L/G126R (dark gray square) compared with control ααTm (white square) (30°C). (A) ATPase activity of reconstituted myofibrils measured in relaxing solution (pCa 9.0). Each point is the mean ± SEM of four measurements (five for control ααTm). The steady-state ATPase rate was obtained from regression lines (dotted lines) fitted on all individual data points. (B) Average slope of regression lines (steady-state rate; s−1) of replaced myofibrils: control ααTm 0.40 ± 0.07; D137L ααTm 0.71 ± 0.13; D137L/G126R ααTm 0.66 ± 0.06. The steady-state rate was significantly increased in D137L/G126R ααTm compared with control ααTm myofibrils (∗p < 0.05, Student’s t-test).