Increased cardiac myosin super-relaxation as an energy saving mechanism in hibernating grizzly bears.

AIM: The aim of the present study was to define whether cardiac myosin contributes to energy conservation in the heart of hibernating mammals.

METHODS

Thin cardiac strips were isolated from the left ventricles of active and hibernating grizzly bears; and subjected to loaded Mant-ATP chase assays, X-ray diffraction and proteomics.

MAIN FINDINGS: Hibernating grizzly bears displayed an unusually high proportion of ATP-conserving super-relaxed cardiac myosin molecules that are likely due to altered levels of phosphorylation and rod region stability.

CONCLUSIONS

Cardiac myosin depresses the heart's energetic demand during hibernation by modulating its function.