RT Journal Article SR Electronic T1 Cryptic genetic variation defines the adaptive evolutionary potential of enzymes JF bioRxiv FD Cold Spring Harbor Laboratory SP 232793 DO 10.1101/232793 A1 Baier, Florian A1 Hong, Nansook A1 Yang, Gloria A1 Pabis, Anna A1 Barrozo, Alexandre A1 Carr, Paul D A1 Kamerlin, Shina CL A1 Jackson, Colin J A1 Tokuriki, Nobuhiko YR 2017 UL http://biorxiv.org/content/early/2017/12/12/232793.abstract AB Genetic variation among orthologous proteins can cause cryptic phenotypic properties that only manifest in changing environments. Such variation may also impact the evolutionary potential of proteins, but the molecular basis for this remains unclear. Here we perform comparative directed evolution in which four orthologous metallo-β-lactamases were evolved toward a new function. We found that genetic variation between these enzymes resulted in distinct evolutionary outcomes. The ortholog with the lower initial activity reached a 20-fold higher fitness plateau exclusively via increasing catalytic activity. By contrast, the ortholog with the highest initial activity evolved to a less-optimal and phenotypically distinct outcome through changes in expression, oligomerization and activity. We show that the cryptic molecular properties and conformational variation of residues in the initial genotypes cause epistasis, thereby constraining evolutionary outcomes. Our work highlights that understanding the molecular details relating genetic variation to protein functions is essential to predicting the evolution of proteins.