Resolving adaptive conflicts of protein structures by gene duplication

Tobias Sikosek

University of Muenster, Institute for Evolution and Biodiversity, Muenster, Germany

Understanding how rapid functional adaptation is possible under complex environmental constraints is crucial not only in the context of long-term genome evolution, but also in critical short-term scenarios such as the evolution of multi-drug resistance in bacteria.

Recent theoretical developments in the area of molecular evolution via gene duplication emphasise the importance of functionally promiscuous ancestors. The concept of subfunctionalisation not only provides a mechanism for retention of otherwise redundant gene copies but also for the "escape from an adaptive conflict". This conflict of a single pre-duplication gene to adapt to more than one selection pressure can lead to a certain degree of multi-functionality prior to a duplication event. After a duplication, the resulting paralogs are thought to quickly specialise on different sub-functions.

Here, multi-functionality is considered at the protein conformational level, assuming a direct link between structure and function. Computer simulations were used to evolve populations of simple lattice model proteins under varying degrees of two selection pressures. Furthermore, the proteins were allowed to duplicate within single individuals in the population. The results show that strong selection pressures are necessary to drive a rapid divergence after duplication of a multi-functional ancestor whereas lower selection pressures slow down the process of divergence to a degree where single-copy multi-functionality remains a viable strategy and duplications do not reach fixation.