Scheduled Seminars on 6/14/2011

Alexander Lobkovsky at 11:00  Edit  Reschedule  Delete

Predictability of evolution in rugged fitness landscapes
Is evolution deterministic, hence predictable, or stochastic, that is unpredictable? What would happen if one could "replay the tape of evolution:" will the outcomes of evolution be completely different or evolution is so constrained that history will be repeated? Arguably, these questions are among the most intriguing and most difficult in evolutionary biology. In more precise terms, the predictability of evolution depends on the fraction of the trajectories on fitness landscapes that are open for evolutionary exploration. Direct experimental investigation of fitness landscapes is extremely technically challenging, so that the available studies only explore a minuscule portion of the landscape for individual enzymes. We sought to investigate the topography of fitness landscapes within the framework of a previously developed model of protein folding and evolution where fitness is equated with robustness to misfolding. It is shown that model-derived and experimental landscapes are significantly smoother than random landscapes and resemble moderately perturbed additive landscapes; thus, these landscapes are substantially robust to mutation. The model shows a deficit of suboptimal peaks even compared with noisy additive landscapes with similar overall roughness. Thus, the smoothness and substantial deficit of peaks in fitness landscapes of protein evolution could be fundamental consequences of the physics of protein folding.


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