Coelimycin inside out - negative feedback regulation by its intracellular precursors

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Streptomyces coelicolor A3(2) is a model organism for antibiotic production.
• Regulation of secondary metabolite biosynthesis gene clusters (BGCs) is complex.
• Biosynthetic products can modulate regulator activity.

Purpose of the Study:

• Investigate the role of intracellular coelimycin precursors (preCPK) in regulating the CPK BGC.
• Characterize the cluster-encoded efflux pump CpkF and its role in CPK production.
• Determine whether intra- or extracellular CPK compounds mediate feedback regulation.

Main Methods:

• Utilized a luciferase-based reporter system to compare promoter activity in wild-type, ΔcpkF, and ΔcpkC strains.
• Generated ΔcpkF mutant lacking the CPK exporter.
• Generated ΔcpkC mutant lacking CPK production.

Main Results:

• Intracellular preCPK is involved in a negative feedback loop, repressing the CPK BGC.
• CpkF is essential for extracellular CPK production.
• Promoter activity was upregulated in ΔcpkC (no CPK) and similar to WT in ΔcpkF (no extracellular CPK), indicating intracellular CPK silences its own production.

Conclusions:

• The CPK polyketide acts as a silencer of its own production, likely through binding an unidentified regulatory protein.
• CpkF is essential for exporting CPK, enabling extracellular accumulation and feedback regulation.
• This study elucidates a novel negative feedback mechanism in antibiotic biosynthesis.