Figure 4

(A) Maximum likelihood tree for subfamily 1 nitrilases used to test for positive selection. Branch lengths are scaled to the mean number of substitutions per codon site under model M3. Branches 1 and 2 indicate lineages tested for positive selection signal, following the transition event. The sequences illustrate the variability across the clade at positions identified under positive selection. (B). A three dimensional model of the 1A21 nitrilase dimer. Shown are the catalytic triad (blue) and the residues under positive selection (red). Residue 39, invariant before and after the transition event, is shown in green.