Publications

• Function and structure of MalA/MalA', iterative halogenases for late-stage C-H functionalization of indole alkaloids.

  Fraley A.E., Garcia-Borras M., Tripathi A., Khare D., Mercado-Marin E.V., Tran H., Dan Q., Webb G.P., Watts K.R., Crews P., Sarpong R., Williams R.M., Smith J.L., Houk K.N., Sherman D.H.

  Malbrancheamide is a dichlorinated fungal indole alkaloid isolated from both Malbranchea aurantiaca and Malbranchea graminicola that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]diazaoctane core. The introduction of chlorine atoms on the indole ring of malbranc ... >> More

  Malbrancheamide is a dichlorinated fungal indole alkaloid isolated from both Malbranchea aurantiaca and Malbranchea graminicola that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]diazaoctane core. The introduction of chlorine atoms on the indole ring of malbrancheamide differentiates it from other members of this family and contributes significantly to its biological activity. In this study, we characterized the two flavin-dependent halogenases involved in the late-stage halogenation of malbrancheamide in two different fungal strains. MalA and MalA' catalyze the iterative dichlorination and monobromination of the free substrate premalbrancheamide as the final steps in the malbrancheamide biosynthetic pathway. Two unnatural bromo-chloro-malbrancheamide analogues were generated through MalA-mediated chemoenzymatic synthesis. Structural analysis and computational studies of MalA' in complex with three substrates revealed that the enzyme represents a new class of zinc-binding flavin-dependent halogenases and provides new insights into a potentially unique reaction mechanism. << Less

  J. Am. Chem. Soc. 139:12060-12068(2017) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Fungal indole alkaloid biogenesis through evolution of a bifunctional reductase/Diels-Alderase.

  Dan Q., Newmister S.A., Klas K.R., Fraley A.E., McAfoos T.J., Somoza A.D., Sunderhaus J.D., Ye Y., Shende V.V., Yu F., Sanders J.N., Brown W.C., Zhao L., Paton R.S., Houk K.N., Smith J.L., Sherman D.H., Williams R.M.

  Prenylated indole alkaloids such as the calmodulin-inhibitory malbrancheamides and anthelmintic paraherquamides possess great structural diversity and pharmaceutical utility. Here, we report complete elucidation of the malbrancheamide biosynthetic pathway accomplished through complementary approac ... >> More

  Prenylated indole alkaloids such as the calmodulin-inhibitory malbrancheamides and anthelmintic paraherquamides possess great structural diversity and pharmaceutical utility. Here, we report complete elucidation of the malbrancheamide biosynthetic pathway accomplished through complementary approaches. These include a biomimetic total synthesis to access the natural alkaloid and biosynthetic intermediates in racemic form and in vitro enzymatic reconstitution to provide access to the natural antipode (+)-malbrancheamide. Reductive cleavage of an L-Pro-L-Trp dipeptide from the MalG non-ribosomal peptide synthetase (NRPS) followed by reverse prenylation and a cascade of post-NRPS reactions culminates in an intramolecular [4+2] hetero-Diels-Alder (IMDA) cyclization to furnish the bicyclo[2.2.2]diazaoctane scaffold. Enzymatic assembly of optically pure (+)-premalbrancheamide involves an unexpected zwitterionic intermediate where MalC catalyses enantioselective cycloaddition as a bifunctional NADPH-dependent reductase/Diels-Alderase. The crystal structures of substrate and product complexes together with site-directed mutagenesis and molecular dynamics simulations demonstrate how MalC and PhqE (its homologue from the paraherquamide pathway) catalyse diastereo- and enantioselective cyclization in the construction of this important class of secondary metabolites. << Less

  Nat. Chem. 11:972-980(2019) [PubMed] [EuropePMC]

  This publication is cited by 11 other entries.