Crystal structures of (A) PBD anthramycin covalently bound to DNA strands and (B) lincomycin targeting the peptidyl transferase center in the 50S ribosomal subunit of Staphylococcus aureus.
Antitumor pyrrolobenzodiazepines (PBDs), lincosamide antibiotics, quorumsensing molecule hormaomycin, and antimicrobial griselimycin are structurally and functionally diverse groups of actinobacterial metabolites. The common feature of these compounds is the incorporation of L -tyrosine- or L -leucine-derived 4-alkyl-L -proline derivatives (APDs) in their structures. In this study, the authors report that the last reaction in the biosynthetic pathway of APDs, catalyzed by F420 H2 -dependent Apd6 reductases, contributes to the structural diversity of APD precursors. Specifically, the heterologous overproduction of six Apd6 enzymes demonstrated that Apd6 from the biosynthesis of PBDs and hormaomycin can reduce only an endocyclic imine double bond, whereas Apd6 LmbY and partially GriH from the biosynthesis of lincomycin and griselimycin, respectively, also reduce the more inert exocyclic double bond of the same 4- substituted Δ 1-pyrroline-2-carboxylic acid substrate, making LmbY and GriH unusual, if not unique, among reductases. Furthermore, the differences in the reaction specificity of the Apd6 reductases determine the formation of the fully saturated APD moiety of lincomycin versus the unsaturated APD moiety of PBDs, providing molecules with optimal shapes to bind their distinct biological targets. Moreover, the Apd6 reductases establish the first F420 H2-dependent enzymes from the luciferase-like hydride transferase protein superfamily in the biosynthesis of bioactive molecules. Finally, bioinformatics analysis demonstrates that Apd6 and their homologues, widely distributed within several bacterial phyla, play a role in the formation of novel yet unknown natural products with incorporated L-proline-like precursors and likely in the microbial central metabolism.
Steiningerova, L.; Kamenik, Z.*; Gazak, R.; Kadlcik, S.; Bashiri, G.; Man, P.; Kuzma, M.; Pavlikova, M. & Janata, J.: Different Reaction Specificities of F420H2‑Dependent Reductases Facilitate Pyrrolobenzodiazepines and Lincomycin To Fit Their Biological Targets, J. Am. Chem. Soc. 2020, 142, 3440-3448, https://dx.doi.org/10.1021/jacs.9b11234