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Adrian T Keatinge-Clay1, David A Maltby, Katalin F Medzihradszky
1Graduate Group in Biophysics, University of California San Francisco, San Francisco, California 94107-2240, USA.
Nature Structural & Molecular Biology
|August 3, 2004
Summary
The structure of actinorhodin ketosynthase-chain length factor (KS-CLF) reveals polyketide elongation within a tunnel. This finding clarifies the roles of KS and CLF in polyketide synthesis, guiding the design of new pharmaceuticals.
Area of Science:
- Biochemistry
- Structural Biology
- Organic Chemistry
Background:
- Aromatic polyketides like actinorhodin, tetracycline, and doxorubicin are synthesized by polyketide synthases (PKSs).
- Type II PKSs utilize a heterodimeric ketosynthase-chain length factor (KS-CLF) complex for polyketide chain polymerization.
Purpose of the Study:
- To elucidate the structural and mechanistic details of the actinorhodin KS-CLF complex.
- To understand the roles of KS and CLF in polyketide chain initiation, elongation, and cyclization.
Main Methods:
- X-ray crystallography to determine the 2.0-Å structure of the actinorhodin KS-CLF complex.
- Structural analysis to identify the polyketide binding site and catalytic mechanisms.
Main Results:
- The structure reveals polyketides elongated within an amphipathic tunnel at the KS-CLF heterodimer interface.
- The ketosynthase (KS) subunit catalyzes both chain initiation and elongation, while the chain length factor (CLF) regulates chain length without an active site.
- Evidence suggests the first polyketide cyclization occurs within the KS-CLF tunnel.
Conclusions:
- The KS-CLF structure provides critical mechanistic insights into type II polyketide biosynthesis.
- Understanding these PKS mechanisms can guide the rational design of novel pharmaceuticals and polymers through biosynthetic chemistry.