Peptide properties predict multistate translocation kinetics via protective antigen nanopores

Area of Science:

• Biophysics
• Nanotechnology
• Biochemistry

Background:

• Understanding guest-host interactions in nanopores is crucial for molecular sensing.
• Anthrax toxin protective antigen (PA) nanopores offer a model system for studying translocation dynamics.
• Peptide translocation mechanisms are complex and influenced by various molecular properties.

Purpose of the Study:

• To elucidate the multi-state kinetic mechanism of peptide translocation through PA nanopores.
• To correlate peptide molecular properties with specific translocation events and energy landscapes.
• To identify the governing physical forces (hydrophobicity, sterics, aromaticity) at each translocation step.

Main Methods:

• Single-molecule analysis of peptide translocations.
• K-Means clustering to identify distinct conductance states (0, 1, 2, 3).
• Multi-exponential kinetic analysis of state-to-state transitions and correlation with peptide properties.

Main Results:

• Four distinct conductance states were identified, including a hydrophobic trap (State 0).
• Entry into the trap is governed by hydrophobicity; escape is size-dependent but aided by aromaticity.
• Inter-state rearrangements are driven by hydrophobicity, while final dissociation depends on the starting state and involves sterics, hydrophobicity, and aromaticity.

Conclusions:

• Peptide translocation through PA nanopores is a multi-step process governed by distinct physical forces.
• Hydrophobicity, sterics, and aromaticity play sequential roles in intra-pore dynamics and release.
• This study provides a detailed energy landscape for peptide-nanopore interactions, advancing molecular translocation understanding.