Summary
The vast majority (93%) of dihydrofolate reductase variants generated by saturation mutagenesis at three important amino acids were fully inactive (1).
See also
1.
Papkou A, Garcia-Pastor L, Escudero JA, Wagner A. A rugged yet easily navigable fitness landscape. Science. 2023;382(6673). Available from: https://doi.org/10.1126/science.adh3860