Investigating the biosynthesis of the ß-branch found in the polyketide difficidin isolated from Bacillus amyloliquefaciens

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Brittany E. Kiel (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Jason Reddick

Abstract: Difficidin is a broad-spectrum antibiotic polyketide product from Bacillus amyloliquefaciens FZB42. Although most of the difficidin structure is made by conventional polyketide synthase (PKS) chemistry, it also contains a small structural feature that is not fully understood. This novel “ß-branch” structure is unusual because it is a disubstituted exocyclic olefin that is likely thermodynamically unstable compared to the tri-substituted ß-branching groups found in other polyketides, such as bacillaene. The hypothesis is that the B. amyloliquefaciens difficidin biosynthetic pathway utilizes a mechanistic route that avoids the thermodynamically stable conjugated trisubstituted double bond while forming the less stable disubstituted ß-branch olefin. Using mass spectrometry and recombinant proteins, the biochemical steps for the biosynthesis of the difficidin ß-branch were investigated and analyzed. The reconstitution of the early steps of the difficidin ß-branch biosynthetic pathway involving the construction of the acetyl- DfnX substrate that provides the extra carbon of the ß-branch were completed first. Then, using a hydroxymethylglutaryl (HMG) group tethered to the acyl carrier di-domain of the modular polyketide synthase DfnJ, a dehydration by BaeH followed by decarboxylation by DfnM successfully generated the B-branch. With this pathway completely reconstituted, we are able to study how the difficidin system constructs the unusual di-substituted ß-branch. [This abstract has been edited to remove characters that will not display in this system. Please see the PDF for the full abstract.]

Additional Information

Language: English
Date: 2019
Acyl Carrier Protein (ACP), Bacillaene, Diffidicin, Polyketide Synthases (PKSs), Polyketide Synthesis, Proteins
Proteins $x Synthesis
Carrier proteins

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