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From a Natural Product to Its Biosynthetic Gene Cluster: A Demonstration Using Polyketomycin from Streptomyces diastatochromogenes Tü6028

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Deconstruction of iterative multidomain polyketide synthase function.

Jason M Crawford¹, Paul M Thomas, Jonathan R Scheerer

¹Department of Chemistry, Johns Hopkins University, Baltimore, MD21218, USA.

Science (New York, N.Y.)

|April 12, 2008

Summary

This summary is machine-generated.

Researchers elucidated the mechanism of aflatoxin B1 biosynthesis by studying the PksA enzyme. They identified key domains and intermediates, revealing how polyketide synthases assemble aromatic compounds.

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Area of Science:

Biochemistry
Molecular Biology
Enzymology

Background:

Aflatoxin B1 is an environmental carcinogen initiated by PksA.
PksA belongs to the poorly understood family of iterative polyketide synthases (IPKSs).

Purpose of the Study:

To understand the catalytic mechanism of PksA, an iterative polyketide synthase.
To identify the roles of individual catalytic domains within PksA.

Main Methods:

Dissecting the PksA enzyme into individual domains.
Reconstituting PksA from selected domain sets.
Characterizing enzyme-bound octaketide intermediates.

Main Results:

Identified specific reactions controlled by individual catalytic domains.
Determined the function of the product template (PT) domain in assembly and cyclization.
Observed the assembly of seven malonyl units onto a hexanoyl starter unit.

Conclusions:

The PT domain, ketosynthase, and thioesterase collaborate to assemble polyketide chains and mediate cyclization.
These mechanistic insights are likely general for aromatic polyketide production by nonreducing IPKSs.