Research from Kent’s School of Biosciences and the University of Colorado Boulder has identified crucial changes in the protein beta myosin that result in the muscles in larger animals contracting more slowly than those of smaller animals. This may lead to a new understanding of mutations in the protein that cause the disease, hypertrophic cardiomyopathy, the most common inherited heart disease.
It is well established that the muscles of larger mammals contract more slowly than smaller animals, best exemplified by the heart. A mouse has a heart rate of 600 beats per minute, while an elephant has a rate of 30 beats per minute. The myosin composition of the heart muscle determines the rate at which contraction occurs. In large mammals, this myosin is called beta.
This research reveals how the beta myosin protein evolved as animal body mass increased to result in the reduced rate of contraction in larger mammals.
The study compared beta myosin protein sequences of a large set of mammals with body masses ranging from 6g to 6,000kg. Using computational approaches, the researchers identified a set of positions in beta myosin that changed in a pattern correlating to species’ body mass. To validate the findings, the team engineered a chimeric beta myosin, that was mainly the human protein but containing the regions associated with body mass from the rat beta myosin.
The biochemical properties of the chimeric beta myosin were tested and the protein exhibited the same properties of the rat protein, thus demonstrating that the positions identified in the original analysis are responsible for determining the rate of muscle contraction.
This research answers a question that has been posed for a long time and is important for our understanding of beta myosin function. This is particularly relevant to heart disease as many cardiomyopathies (a type of heart disease) are caused by mutations to the beta myosin protein that is present in the heart.
Michael Geeves, Professor of Physical Biochemistry in the University of Kent and a lead author of the study, said: ‘This work highlights how beta myosin has evolved as body mass has increased and the speed of muscle contraction has reduced. Beta myosin is present in muscles including the heart and mutations in beta myosin are known to cause a type of heart disease called cardiomyopathies. Our research identifies regions within beta myosin that play an important functional role in beta myosin and further expand our understanding of this protein. Such understanding can be applied to research on mutations that cause cardiomyopathies.’
The paper ‘Identification of sequence changes in myosin II that adjust muscle contraction velocity’ is published by PLOS Biology (Dr Chloe Johnson, Jake McGreig, Sarah T Jeanfavre, Dr Jonathan Walklate, Dr Marta Farré Belmonte, Professor Daniel Mulvihill, Dr Anthony Baines, Dr Mark Wass, Professor Michael Geeves – School of Biosciences; Professor Martin Ridout – School of Mathematics, Statistics and Actuarial Science, University of Kent; Carlos Vera, Professor Leslie Leinwand – BioFrontiers Institute and Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder).
URL: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001248