Mava and PKA specifically alter the relative populations of SRX states in different thick filament zones. (a and c) In the presence of mava (a), the populations of active, DRX, and SRX myosins are plotted relative to untreated thick filaments (n_events = 3,315, n_myofibrils = 11) and also as (c) percent populations within each zone. A significant difference in the DRX population of the C-zone (P = 0.0003) and in each population of the D-zone (active P = 0.0013, DRX P = 0.0001, SRX P = 0.0028) was observed. (b and d) With PKA (n_events = 2,705, n_myofibrils = 20), the changes relative to untreated are shown in b, whereas d shows the percent populations within each zone. See Table 1 for values. Significant changes were observed in all populations of the C-zone (active P = 0.0101, DRX P = 0.0001, SRX P = 0.0034), but only for the DRX in the P-zone (P = 0.0001). (e) To better represent the shift between DRX and SRX populations, the ratio of SRX:DRX is plotted revealing a clear significant effect of mava (P = 0.0093) and PKA (P = 0.0001) in the C-zone, whereas only mava (P = 0.0001) and not PKA affects the ratio of heads in the D-zone. Asterisks denote significant differences in values from untreated (Fig. 3 d), determined using an unpaired two-tailed t test (P < 0.05). The number of myofibrils was used as n values during statistical analysis.