Fast heart, slow heart: Changes in the molecular motor myosin explain the difference

The human heart contracts about 70 times per minute, while that of a rat contracts over 300 times; what accounts for this difference? In a new study publishing 10th June in the open-access journal PLOS Biology, led by Michael Geeves and Mark Wass of the University of Kent and Leslie Leinwand from the University of Colorado Boulder, reveal the molecular differences in the heart muscle protein beta myosin that underly the large difference in contraction velocity between the two species.