Controlling dissociation channels of gas-phase protein complexes using charge manipulation

Area of Science:

• Biophysics
• Computational Biology
• Protein Dynamics

Background:

• Transthyretin (TTR) is a tetrameric protein complex.
• Understanding protein complex dissociation is crucial for biological and therapeutic applications.
• The role of charge distribution and N-termini in TTR unfolding is not fully understood.

Purpose of the Study:

• To investigate the mechanism of monomer unfolding in a positively charged tetrameric transthyretin (TTR) complex.
• To explore the influence of N-termini and charge distribution on TTR complex stability and dissociation.
• To assess the potential of experimentally modifying TTR to control its unraveling.

Main Methods:

• Coarse-grained simulations were employed to model a tetrameric TTR complex with a +20 charge.
• Charge hopping simulations were conducted at 300 K and 600 K under three scenarios: normal charge mobility, blocked N-termini protonation, and tethered charge tag.
• Calculations included charge distributions and radii of gyration to monitor monomer unfolding and charging.

Main Results:

• The N-terminus plays a critical role in initiating monomer unfolding through a zipper-like mechanism.
• Simulations at 600 K showed distinct unfolding patterns compared to 300 K.
• Altering N-termini protonation or introducing a charge tag significantly impacted unfolding and charging dynamics.

Conclusions:

• The N-terminus is a key driver of TTR monomer unfolding.
• Experimental modifications, such as tethering or blocking N-termini protonation, offer potential strategies to control TTR complex unraveling and dissociation.
• These findings provide insights into protein complex stability and dissociation mechanisms.