Effect of bacterial Hsp90 on the evolution of fluorescent protein

By facilitating folding of protein clients, chaperones can affect adaptive protein evolution. In this work we study how the bacterial Hsp90 chaperone affects the evolution of green fluorescent protein. To this end, we performed directed evolution of GFP under low and high cellular concentrations of Hsp90. Specifically, we evolved GFP under both stabilizing selection for its ancestral (green) phenotype, and directional selection towards a new (cyan) phenotype. While Hsp90 affected the rate of adaptive evolution only transiently, it did affect the phenotypic effects of mutations that occurred during adaptive evolution.