Trigger factor from Thermus thermophilus is a Zn2+-dependent chaperone

Area of Science:

• Molecular biology
• Protein biochemistry
• Chaperone proteins

Background:

• Ribosome-associated chaperones, like trigger factor (TF) in Escherichia coli, are crucial for nascent polypeptide folding.
• The function and regulation of TFs in thermophilic bacteria remain less understood.

Purpose of the Study:

• To investigate the folding-arrest activity of trigger factor (TF) from the thermophilic eubacterium Thermus thermophilus.
• To determine the role of metal ions, specifically zinc (Zn2+), in the chaperone activity of Thermus thermophilus TF.

Main Methods:

• Formation and isolation of a binary complex between Thermus thermophilus TF and green fluorescent protein (GFP).
• Gel-filtration chromatography to assess complex stability and dynamics.
• Assay of TF folding-arrest activity in the presence and absence of EDTA and varying Zn2+ concentrations.

Main Results:

• Thermus thermophilus TF forms a dynamic 1:1 binary complex with GFP, arresting its spontaneous folding.
• EDTA treatment abolished TF's folding-arrest activity, revealing an approximate 0.5 mol Zn2+/mol TF in the preparation.
• Zn2+-saturated TF exhibited twice the folding-arrest activity compared to untreated TF, indicating Zn2+ dependence.

Conclusions:

• The chaperone activity of Thermus thermophilus TF is dependent on zinc ions (Zn2+).
• Zinc binding significantly enhances the folding-arrest efficiency of thermophilic TF.
• This finding provides new insights into the regulation and function of chaperones in thermophilic organisms.