DNA Cleavage by a De Novo Designed Protein-Titanium Complex

Area of Science:

• Biochemistry
• Bioinorganic Chemistry
• Protein Engineering

Background:

• Titanium, an abundant element, is typically excluded from biological roles due to its susceptibility to hydrolysis.
• Nature employs mechanisms to stabilize hard Lewis acidic metals using biological ligands, offering a model for titanium stabilization.
• The Due Ferri single-chain (DFsc) protein was previously engineered to bind and stabilize iron ions.

Purpose of the Study:

• To investigate the stabilization of titanium ions using a designed protein scaffold.
• To explore the biological activity of a novel titanium-protein complex.
• To demonstrate the potential of engineered proteins in coordinating and functionalizing otherwise biologically incompatible metals.

Main Methods:

• Utilized the de novo designed Due Ferri single-chain (DFsc) protein scaffold.
• Demonstrated titanium ion (Ti4+) binding to the DFsc scaffold, assessing stability against hydrolysis.
• Evaluated the DNA-cleaving activity of the resulting Ti4+-DFsc complex on plasmid DNA.

Main Results:

• The DFsc scaffold successfully bound two equivalents of titanium ions (Ti4+).
• The protein protected the bound titanium from hydrolysis, forming a stable complex.
• The Ti4+-DFsc complex exhibited catalytic activity, linearizing plasmid DNA in vitro.
• This represents the first documented instance of a functional, soluble titanium-protein complex.

Conclusions:

• Engineered protein scaffolds can overcome the hydrolytic instability of titanium, enabling its biological application.
• The Ti4+-DFsc complex is a novel biomimetic tool with DNA-cleaving capabilities.
• This work establishes a precedent for utilizing designed proteins to create functional complexes with abundant, yet challenging, metal ions.