Interchenar retrotransfer of aureothin intermediates in an iterative polyketide synthase module

Area of Science:

• Biochemistry
• Molecular Biology
• Synthetic Biology

Background:

• Polyketide synthases (PKS) are crucial for producing diverse natural products.
• The iterative mechanism of PKS module utilization remains incompletely understood.
• Aureothin biosynthesis involves a complex PKS assembly line.

Purpose of the Study:

• To elucidate the iterative mechanism of a PKS module in aureothin assembly.
• To investigate the role of specific domains, including the N-terminus of AurA, in PKS iteration.
• To test alternative models for polyketide intermediate transfer during biosynthesis.

Main Methods:

• Targeted domain inactivation within the aureothin PKS assembly line.
• Construction and functional analysis of PKS heterodimers with specific domain deletions.
• Complementation studies in a PKS deletion mutant (ΔaurA).

Main Results:

• The N-terminus of AurA was found to be dispensable for the iterative PKS process.
• An AurA(KS°, ACP°)-AurA(AT(0)) heterodimer was nonfunctional, indicating essential roles for KS and ACP domains.
• Restoration of aureothin production in a ΔaurA mutant complemented with AurA(KS°)-AurA(ACP°) supports a specific transfer model.

Conclusions:

• The study refutes an ACP-ACP shuttle model for iterative PKS function.
• Evidence supports a model where the ACP-bound polyketide intermediate is transferred back to the KS domain on the opposing PKS strand.
• This work clarifies a key step in the complex biosynthesis of polyketides like aureothin.