Evolutionary Reprogramming of Acyltransferase Domains in Polyene Macrolide Pathways.

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• The evolutionary pathways of type I polyketide synthase (T1PKS) assembly lines are not well understood.
• Polyketides are a diverse class of natural products with significant therapeutic potential.

Purpose of the Study:

• To investigate the evolution of T1PKS assembly lines.
• To understand the functional reprogramming of acyltransferase (AT) domains in polyketide biosynthesis.
• To explore novel mechanisms for polyketide structural diversification.

Main Methods:

• Systematic mining of polyene biosynthetic gene clusters.
• Biochemical analysis of acyltransferase (AT) and ketosynthase (KS) domains.
• Engineering of the candicidin pathway using insights from the eurocidin pathway.

Main Results:

• Identified a novel eurocidin biosynthetic pathway with divergent loading module architectures, representing an evolutionary transitional state.
• Demonstrated functional reprogramming of AT domains, enabling substrate specificity shift from extender units (malonyl-CoA) to starter units (acyl-CoA).
• Observed parallel evolution of KS domains (KSS→KSQ mutations) diversifying initiation strategies.
• Engineered the candicidin pathway to produce aliphatic-starting analogs by incorporating a starter-selective monomodule from eurocidin.

Conclusions:

• Functional plasticity of AT domains is a novel mechanism for polyketide structural diversification, explaining the origin of AT-initiated assembly lines.
• Evolution-inspired AT reprogramming provides a rational framework for modifying polyketide starter units.
• This approach expands structural diversity and enhances the therapeutic potential of polyketides.