The Enterococcus hirae copper chaperone CopZ delivers copper(I) to the CopY repressor

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Copper homeostasis is crucial for bacterial survival and is regulated by specific proteins.
• In Enterococcus hirae, the cop operon controls copper homeostasis and is regulated by the copper-responsive repressor CopY.
• Purified Zn(II)CopY has been shown to bind to a synthetic cop promoter fragment in vitro.

Purpose of the Study:

• To investigate the role of the protein CopZ in copper homeostasis.
• To elucidate the mechanism by which CopZ interacts with CopY and DNA.
• To characterize the transfer of copper ions between CopZ and CopY.

Main Methods:

• Gel filtration chromatography to assess protein interactions and complex formation.
• Luminescence spectroscopy to monitor copper binding and transfer.
• In vitro binding assays using purified proteins and DNA fragments.

Main Results:

• The 8 kDa protein CopZ functions as a copper chaperone, specifically delivering copper(I) to Zn(II)CopY.
• Copper transfer from CopZ to CopY results in the release of CopY from the DNA promoter.
• Two copper(I) ions are quantitatively transferred from Cu(I)CopZ to Zn(II)CopY, displacing zinc(II).
• Copper is transferred from an exposed, non-luminescent site in CopZ to a shielded, luminescent site in CopY.

Conclusions:

• CopZ is a key copper chaperone involved in regulating the cop operon in Enterococcus hirae.
• The interaction between CopZ and CopY is essential for copper-mediated gene regulation.
• This study reveals the molecular mechanism of copper transfer and its impact on DNA binding regulation.