Fig. 4.

Sequence optimality of the interface residues of I-AniI. Heat map displaying the frequencies observed of each amino acid type in a selected pool of sequences at each of 44 positions in the I-AniI interface. The wild-type amino acid is marked with a green box. Each position in the interface was fully randomized, and these single-position libraries were subject to an activity selection.²⁸ A frequency of 1 means that the amino acid with this frequency was the only amino acid type observed at that protein position, whereas a frequency of 0.05 would be an amino acid type observed once from a set of 20 sequences.