Natural Product Biosynthesis
Nonribosomal peptide and polyketide natural
products are assembled on large, multidomain and
multimodule megasynthase enzymes. The amino acid
building blocks are polymerized through a
thioester-templated mechanism. The rational, linear
organization of these systems favors engineering
approaches toward the production of novel compounds.
The lack of detailed structural and mechanistic
information for multidomain synthases hinders the
mechanistic understanding and rational engineering
of these systems. In particular, the
structural dynamics of the carrier domains and the
details of substrate trafficking remain largely
The complex structure and functionality of
therapeutically important natural products is often
the result of interesting and unusual enzymology.
For example, the enzyme DpgC catalyzes a key step in
the biosynthesis several natural products including
the vancomycin/teicoplanin antibiotics, important
drugs that are frequently used as the last line of
defense for aggressive, multidrug-resistant
infections. DpgC is a cofactor/metal-independent
dioxygenase in the pathway to the nonproteinogenic
amino acid 3,5-dihydroxyphenylglycine. The
mechanistic details for cofactor-independent
oxygenases are unusual and the specific chemistry of
DpgC has little precedent.
Natural product discovery
In addition we are exploring novel natural product pathways through "genome mining" approaches. For example, we are exploiting a system more amenable to crystallographic analysis, a novel nonribosomal peptide pathway from the thermophile T. fusca. In general, proteins from thermophilic hosts exhibit enhanced stability favoring structural and biochemical characterization. We identified a single gene cluster in T. fusca corresponding to a multimodular nonribosomal peptide secondary metabolite biosynthetic pathway and determined the structure using NMR/MS techniques. The results established a novel structural architecture in the siderophore family of natural products. Current and future work is aimed at structurally characterizing all enzymes in this pathway to provide a complete structural basis for nonribosomal peptide natural product biosynthesis.