Evidence for conformational changes upon copper binding to Cupriavidus metallidurans CzcE

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• CzcE is a periplasmic protein in Cupriavidus metallidurans CH34.
• It is known to bind four copper atoms per dimer.

Purpose of the Study:

• To determine the structure of the apo form of CzcE.
• To identify key residues involved in copper binding.
• To understand how CzcE interacts with different copper oxidation states.

Main Methods:

• X-ray crystallography to determine protein structure.
• Site-directed mutagenesis and UV-visible spectroscopy to confirm residue function.
• X-ray absorption spectroscopy to analyze copper coordination.
• Proteolysis experiments to study conformational changes.

Main Results:

• The apo form of CzcE was crystallized and its structure determined at 1.85 A resolution.
• His24 and Asp100 were identified as key residues for Cu(II) binding.
• CzcE binds four Cu(II) atoms in its oxidized form and four Cu(I) atoms in its reduced form.
• Different conformational changes occur upon binding of Cu(II) versus Cu(I).

Conclusions:

• CzcE undergoes distinct conformational changes depending on the copper oxidation state.
• These changes, along with its copper-binding ability, suggest a role in copper sensing for Cupriavidus metallidurans CH34.