A pH Switch for β-Sheet Protein Folding

Area of Science:

• Protein Engineering
• Biotechnology
• Structural Biology

Background:

• Advancements in protein design focus on creating stable and specific protein structures.
• Controlling protein folding and stability is crucial for biotechnological applications.

Purpose of the Study:

• To engineer a novel 6-residue sequence (HPATGK) that functions as a pH-switchable structure-nucleating turn.
• To investigate the impact of this pH-switch sequence on the folding stability of beta-sheets.

Main Methods:

• Introduction of the HPATGK sequence into the turn of a standard 3-stranded beta-sheet model (WW domain).
• Analysis of folding characteristics and melting temperature (Tm) at varying pH levels (pH 8 and pH 2.5).
• Thermodynamic analysis to quantify the change in folding free energy (ΔΔGF).

Main Results:

• The HPATGK sequence acted as a stable turn at physiological and higher pH.
• A significant drop in melting temperature (Tm) of approximately 50°C was observed at pH 2.5 compared to pH 8.
• The insertion resulted in a substantial change in folding stability (ΔΔGF ≥11.3 kJ mol⁻¹).

Conclusions:

• The engineered HPATGK sequence effectively introduces a pH-dependent folding switch into beta-sheet structures.
• This strategy allows for the design of proteins with tunable conformational stability based on pH.
• The findings pave the way for creating novel biomolecular tools with controllable conformational changes.