FIG. 4.

Direct assessment of the deaminase activities of the A3H variants using a bacterial mutator assay. (A) Bacterial expression plasmids encoding the different A3H variants were electroporated into E. coli BW310. Eight colonies of each construct were picked and cultured overnight in the presence of IPTG. Bacteria were plated on rifampin plates, and Rif-resistant colonies were counted the next day. Bacterial concentrations were measured by the OD₆₀₀ in a spectrometer and used to correct the number of counted Rif-resistant colonies. (B) The deaminase activities and the respective expression levels of two independent experiments were used. The deaminase mutants were excluded from the correlation between deaminase activity and protein expression (Spearman correlation of 0.949; P < 0.01).