Key result
Tropomyosin strands rolling on the thin filament surface during the ATPase cycle increase the amplitudes of multistep changes in the spatial arrangement of the SH1 helix and subdomain-1 at force generation states, an effect enhanced by high-Ca2+ troponin.
Why the study?
New data on the molecular mechanism of the regulation of ATPase cycle by the troponin-tropomyosin system in striated muscle were needed to understand the azimuthal movements during ATPase cycle steps.
Experimental study demonstrates how tropomyosin movement coordinates actin-myosin conformational shifts in muscle fibers, suggesting a mechanism that enhances cross-bridge work efficiency.
New data on the molecular mechanism of the regulation of ATPase cycle by troponin-tropomyosin system have been obtained in reconstructed muscle fibers by using the polarized fluorescence technique, which allowed us following the azimuthal movements of tropomyosin, actin subdomain-1 and myosin SH1 helix motor domain during the sequential steps of ATPase cycle. We found that tropomyosin strands "rolling" on thin filament surface from periphery to center at ATPase cycle increases the amplitudes of multistep changes in special arrangement of SH1 helix and subdomain-1 at force generation states. These changes seem to convey to actin monomers and to myosin "lever arm", resulting in enhance of the effectiveness of each cross-bridge work. At high-Ca^2+^ troponin, a shift of tropomyosin strands further to center at strong-binding states increases this effect. At low-Ca^2+^ troponin "freezes" tropomyosin and actin in states typical for weak-binding states, resulting in disturbing the teamwork of actin and myosin.
No takes yet. Share an insight, caveat, or question.
Borovikov et al. (2007) studied this question. Troponin-tropomyosin system regulation was evaluated on Conformational changes and mobility of tropomyosin, actin subdomain-1, and myosin SH1 helix during the ATPase cycle (p=<0.05). Tropomyosin strands rolling on the thin filament surface during the ATPase cycle increase the amplitudes of multistep changes in the spatial arrangement of the SH1 helix and subdomain-1 at force generation states, an effect enhanced by high-Ca2+ troponin.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: