Figure 5. Mutagenesis at the proposed transacylation site. a) A
stereodiagram of the top solution for PikACP6 and PikKS6 show residues
in and around the interface targeted for mutational analysis (yellow).
b) The model triketide lactone synthase,P1 -P6 -P7 , was employed to measure the effects
of mutating individual residues on the surface of PikKS6 (*). Triketide
lactone peak areas from LC/MS analysis (triplicate experiments, standard
deviations shown) were made on media extracts from 8 d cultures (Data
File 80). The KS residues whose sidechains are hypothesized to make the
most contact with ACP, N275 and L315, were the most sensitive to
mutation. Generally, mutations to positions farther from the proposed
interface resulted in smaller losses in activity.