The Analysis of Myosin II Evolution in Mammals

Myosin-II is a family of myosin that contains fifteen different isoforms that vary in function, from maintaining a critical role in sarcomeric contractions to non-muscle movement. Myosin-IIs structure can be divided in to two key domains, the motor domain and the tail domain. It is the motor domain that contains the proteins catalytic activity. The observed phenomenon of an inverse relationship between organism size and heart rate tells us that heart rates do vary with size. The larger the animal mass, the slower the heart rate. This phenomenon allowed us to propose the idea that variations in the sequence of cardiac isoforms could be observed as mass of the species increases, due to the variance of heart rates. If so, any divergence seen in the sequence of the ?-cardiac isoform would be reflected as species mass increases should not be seen in other isoforms that do not rely on heart rate variability. Through analysing the sequences of twelve mammalian species of varying mass, a strong divergence relationship was observed in the ?-cardiac motor domain with a correlation coefficient of -0.945 that was no observed in other isoforms. Key results show that myosin sequence divergence does have a marked dependence on both evolutionary separation and size difference between species.