CorE from Myxococcus xanthus is a copper-dependent RNA polymerase sigma factor

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Copper is essential but toxic, requiring strict cellular homeostasis in all organisms.
• Bacteria possess numerous copper detoxification and homeostasis mechanisms.
• The prokaryote Myxococcus xanthus has multiple copper-regulated proteins.

Purpose of the Study:

• To characterize the role of the ECF sigma factor CorE in Myxococcus xanthus copper homeostasis.
• To elucidate the mechanism of CorE-mediated gene regulation by copper.
• To identify a novel class of metal-responsive sigma factors.

Main Methods:

• In vitro DNA binding assays using purified CorE protein.
• Gene expression analysis following copper addition.
• Site-directed mutagenesis of CorE's C-terminal domain.
• Comparative genomic studies.

Main Results:

• CorE requires copper for DNA binding and regulates genes involved in copper homeostasis.
• CorE activity is modulated by copper's redox state: activated by Cu(II), inactivated by Cu(I).
• A Cys-rich C-terminal domain is crucial for CorE's activation and inactivation by copper.

Conclusions:

• CorE represents a novel mechanism of metal-responsive gene regulation.
• A new group of ECF sigma factors, mechanistically distinct from known regulators, is proposed.
• Understanding CorE provides insights into bacterial metal homeostasis and regulatory networks.