Figure 4. Assessment of IHM/SRX state... | Rockefeller University Press

Figure 4.

$Assessment of IHM/SRX state fraction via single mantATP turnover. (a–d) Single turnover of mantATP by β-cardiac myosin constructs was analyzed at different KCl concentrations to deduce the fraction of myosin heads in the IHM/SRX state. WT and E525K constructs at 0.25 µM were preincubated with mantATP (1 µM) for ∼30 s before introducing saturating ATP (2 mM). The fluorescence transients were fitted to a two-exponential decay function to infer the SRX state’s fraction and kinetics. Notably, long-tailed (15 and 25HEP; c and d) constructs displayed a greater SRX fraction than S1 or 2HEP (a and b), which was sensitive to salt concentration only in the WT constructs with significant differences identified by asterisks (*) (15HEP, P < 0.005; 25HEP, P < 0.05). The mean ± SD of three experiments from separate protein preparations is reported in panels a, b, and d. Data in c originally published in Rasicci et al. (2022). Comparison P values provided in Tables S3 and S4.$

Assessment of IHM/SRX state fraction via single mant ATP turnover. (a–d) Single turnover of mantATP by β-cardiac myosin constructs was analyzed at different KCl concentrations to deduce the fraction of myosin heads in the IHM/SRX state. WT and E525K constructs at 0.25 µM were preincubated with mantATP (1 µM) for ∼30 s before introducing saturating ATP (2 mM). The fluorescence transients were fitted to a two-exponential decay function to infer the SRX state’s fraction and kinetics. Notably, long-tailed (15 and 25HEP; c and d) constructs displayed a greater SRX fraction than S1 or 2HEP (a and b), which was sensitive to salt concentration only in the WT constructs with significant differences identified by asterisks (*) (15HEP, P < 0.005; 25HEP, P < 0.05). The mean ± SD of three experiments from separate protein preparations is reported in panels a, b, and d. Data in c originally published in Rasicci et al. (2022). Comparison P values provided in Tables S3 and S4.