Beyond phylogenetics II: Tandem Darwinian evolution of α and β, tubulin

Abstract Cytoskeletons contain polymerized proteins: actin, tubulin, and motor proteins such as myosin, kinesin and dynein. Their positive Darwinian evolution is quantified in the context of approach to optimized functionality (self-organized criticality), using hydropathic waves. Our analysis reveals the functional differences between the polymerizing α and β tubulin monomers, which are similar in length and secondary structures, as well as having indistinguishable phylogenetic trees. We show how evolution has improved flexibility especially for α tubulin, and thus facilitated heterodimer microtubule assembly, in agreement with recent atomistic simulations. We conclude that the failure of phylogenetic analysis to identify functionally specific positive Darwinian evolution has been caused by 20th century technical limitations. These are overcome using 21st century thermodynamic scaling and modular averaging.