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Polyketide synthases (PKSs) contain loops with amino acid repeats. These loops, especially near dehydratase domains, show limited tolerance to changes, impacting PKS engineering.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Synthetic Biology

Background:

  • Modular polyketide synthases (PKSs) are complex enzymes responsible for producing diverse polyketide natural products.
  • Interdomain loops within PKS modules are crucial for enzymatic function but remain largely uncharacterized.
  • Amino acid repeats within these loops often arise from genetic events like slipped-strand mispairing.

Purpose of the Study:

  • To catalog tandem repeats in PKS loops and identify their locations within modules.
  • To determine the tolerance of PKS loops to amino acid alterations.
  • To inform the engineering of PKS systems for novel molecule production.

Main Methods:

  • Cataloging tandem repeats in DNA encoding 949 modules from 129 cis-acyltransferase PKSs.
  • Identifying the locations of corresponding amino acids within PKS modules.
  • Analyzing the distribution and frequency of loop insertions across different PKS domains.

Main Results:

  • The most frequent loop insertions occur at the module boundary downstream of the ketosynthase (KS) domain.
  • Loops adjacent to the dehydratase domain exhibit very low tolerance to insertions.
  • No repetitive loop insertions were found in the acyl carrier protein (ACP) domain, and only two in the KS domain.

Conclusions:

  • PKS interdomain loop tolerance to amino acid changes varies significantly depending on location within the module.
  • The ketosynthase and dehydratase domains are sensitive to alterations, while the ACP domain appears intolerant to repetitive insertions.
  • Understanding loop tolerance is key for the rational design and engineering of PKS assembly lines.