Temperature dependence of sliding velocity of F-actin and reconstituted thin filaments at pCa 5. (A) Relationship between the distance from the heat source and sliding velocity for F-actin. (B) Same as in A for reconstituted thin filaments. (C) Sliding velocity plotted against temperature. Closed circles, F-actin; open circles, reconstituted thin filaments. Sliding velocities were compared at 25°C (baseline temperature) and at higher temperatures raised by IR laser irradiation. Data represent mean ± SEM for both the x and y axes. Sliding velocities at 25°C are 4.5 ± 0.05 µm/s (n = 461) and 6.4 ± 0.1 µm/s (n = 352) for F-actin and reconstituted thin filaments, respectively. Those at higher temperatures are as follows: 12.6 ± 0.4 (n = 21) and 14.0 ± 0.3 µm/s (n = 32) at 34.2 ± 0.5 and 34.4 ± 0.4°C, 15.6 ± 0.3 (n = 69) and 15.4 ± 0.3 µm/s (n = 61) at 35.9 ± 0.3 and 36.1 ± 0.4°C, 18.0 ± 0.4 (n = 69) and 17.1 ± 0.3 µm/s (n = 72) at 37.9 ± 0.6 and 37.9 ± 0.6°C, 20.0 ± 0.3 (n = 119) and 17.9 ± 0.3 µm/s (n = 112) at 40.7 ± 0.7 and 41.0 ± 0.7°C, and 18.5 ± 0.7 (n = 45) and 17.4 ± 0.6 µm/s (n = 38) at 45.6 ± 1.7 and 44.9 ± 1.0°C for F-actin and reconstituted thin filaments, respectively. **, P < 0.01; ***, P < 0.001 for the y axis between groups (no significant differences were present on the x axis for each comparison). (D) Arrhenius plot of sliding velocity for F-actin and reconstituted thin filaments. T, absolute temperature. The average values from C were used. Data obtained in the highest temperature range (shown in gray) were not employed for the analysis (see Fig. 3 legend). Sliding velocity (V) and temperature were expressed in logarithm. F-actin: V = exp (32.65 − 9,269/T) (R = 0.97). Reconstituted thin filaments: V = exp (23.24 − 6,358/T) (R = 0.96). Closed circles with a black solid line, F-actin; open circles with a red solid line, reconstituted thin filaments. Q₁₀ (25–41°C), 2.6 and 1.9 for F-actin and reconstituted thin filaments, respectively.