LAUSR

Mutation at a single amino acid alters the isoprene donor specificity of prenyltransferases involved in the modification of ribosomally synthesized and post-translationally modified peptides (RiPPs). While most characterized RiPP prenyltransferases carry out the regiospecific transfer of C5 dimethylallyl donor to the side chain atoms on macrocyclic acceptor substrates, the elucidation of the cyanobactin natural product piricyclamide 70005E1 identifies an O-geranyl modification on Tyr, a reaction with little prior biochemical precedence. Reconstitution and kinetic studies of the presumptive geranyltransferase PirF shows that the enzyme utilizes a C10 donor, with no C5 transferase activity. The crystal structure of PirF reveals a single amino acid difference in the vicinity of the isoprene-binding pocket, relative to the C5 utilizing enzymes. Remarkably, only a single amino acid mutation is necessary to completely switch the donor specificity from a C5 to a C10 prenyltransferase, and vice versa. Lastly, we ...