6NKH

Structure of MalC Reductase/Diels-Alderase from Malbranchea aurantiaca

Summary for 6NKH

• Entry DOI: 10.2210/pdb6nkh/pdb
• Descriptor: Short chain dehydrogenase (2 entities in total)
• Functional Keywords: reductase, diels-alderase, oxidoreductase
• Biological source: Malbranchea aurantiaca
• Total number of polymer chains: 4
• Total formula weight: 113055.54

Authors

Dan, Q.,Newmister, S.A.,Smith, J.L.,Sherman, D.H. (deposition date: 2019-01-07, release date: 2019-10-09, Last modification date: 2024-03-13)

Primary citation

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.
Fungal indole alkaloid biogenesis through evolution of a bifunctional reductase/Diels-Alderase.
Nat.Chem., 11:972-980, 2019

PubMed Abstract: 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.

PubMed: 31548667
DOI: 10.1038/s41557-019-0326-6

Experimental method

X-RAY DIFFRACTION (1.6 Å)