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. 2021 Apr 20;120(11):2222–2236. doi: 10.1016/j.bpj.2021.04.007

Figure 8.

Figure 8

Impact of R723G and F764L mutants on the power-stroke rate constant in M2β-S1. Sequential-mix stopped-flow experiments were performed as described in Fig. 4. The rate constants of the fast phase were plotted as a function of actin concentration and fitted to a hyperbolic function to determine the maximal rate of power stroke for (A) R723G, 10.8 ± 4.1 s−1 or (B) F764L, 8.7 ± 4.5 s−1. The slow phase was also actin-concentration dependent for both mutants, with a rate of 0.9 ± 0.2 s−1 for R723G and 0.8 ± 0.3 s−1 for F764L at 30 μM actin. Data points at each actin concentration represent the average ± SEM of three experiments from separate protein preparations. The fast phase of the power stroke for WT is replotted from Fig. 4 for comparison with the mutants. Student’s t-tests were performed at each actin concentration to compare each mutant with WT, and significant differences were found at 30 μM actin in R723G and 20 and 30 μM actin in F764L (∗p < 0.05).