Fig. 3. The amino acid distribution observed in deep sequencing of the activity-sorted MKK1 variants.

a Proportional Venn diagram displaying the number of unique sequences found in the low activity gate (≥3 sequencing reads, red), medium activity gate (≥5 sequencing reads, yellow) and the high-activity gate (≥10 sequencing reads, green). b The enrichment of observed amino acids ($f_a^{obs}$) at each position in the final active set of n = 29,563 variants found in the high gate, relative to expected frequencies ($f_a^{id}$) in a perfectly balanced library.