The Ketosynthase Domain Controls Chain Length in Mushroom Oligocyclic Polyketide Synthases

Abstract

The nonreducing iterative type I polyketide synthases (NR-PKSs) CoPKS1 and CoPKS4 of the webcap mushroom Cortinarius odorifer share 88 % identical amino acids. CoPKS1 almost exclusively produces a tricyclic octaketide product, atrochrysone carboxylic acid, whereas CoPKS4 shows simultaneous hepta-and octaketide synthase activity and also produces the bicyclic heptaketide 6-hydroxymusizin. To identify the region(s) controlling chain length, four chimeric enzyme variants were constructed and assayed for activity in Aspergillus niger as heterologous expression platform. We provide evidence that the β-ketoacyl synthase (KS) domain determines chain length in these mushroom NR-PKSs, even though their KS domains differ in only ten amino acids. A unique proline-rich linker connecting the acyl carrier protein with the thioesterase domain varies most between these two enzymes but is not involved in chain length control.

Combinatorial biosynthesis for the engineering of novel fungal natural products

“…However, when the SAT-KS-AT, or SAT-KS-AT-PT domains were swapped, the major compound was a C 18 polyketide, revealing that control of chain length resides within the KS domain 27 . KS domain swaps between NR-PKS CoPKS1, which synthesizes the octaketide atrochrysone carboxylic acid, and CoPKS4, which synthesizes both octaketides and heptaketides such as 6-hydroxymusizin, further corroborated the role of the KS domain in controlling polyketide chain length and identified ten amino acid residues that may be involved 28 .…”

Domain Truncation in Hispidin Synthase Orthologs from Non-Bioluminescent Fungi Does Not Lead to Hispidin Biosynthesis

“…Polyketide synthases are sensitive to even small changes in sequence [ 16 ], and close polyketide synthase homologs can produce different compounds [ 17 , 18 ]. The mutual orientation of the domains and the linkers between them was shown to be important for the product formation [ 18 , 19 ].…”

“…Polyketide synthases are sensitive to even small changes in sequence [ 16 ], and close polyketide synthase homologs can produce different compounds [ 17 , 18 ]. The mutual orientation of the domains and the linkers between them was shown to be important for the product formation [ 18 , 19 ]. The polyketide synthases selected for the present study differed in the linker sequences between the domains ( Supplementary Information S1 ), which may explain the differences in their ability to produce hispidin-like styrylpyrones.…”

Structural enzymology of iterative type I polyketide synthases: various routes to catalytic programming

“…The evidence of chain length controlled by KS has also been shown by a domain swap of the two closely related NR-iPKS CoPKS1 and CoPKS4, in which it is the KS domain that determines whether the dominant product is hepta-or octaketide. 46 The second perception comes from the bacterial type II HR-iPKS Iga11-Iga12 47 (Fig. 8B).…”