Single-residue physicochemical characteristics kinetically partition membrane protein self-assembly and aggregation

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Most transmembrane proteins aggregate, contributing to neurodegenerative diseases.
• Understanding membrane protein aggregation mechanisms is crucial due to rising disease incidence.

Purpose of the Study:

• To investigate how subtle protein sequence variations influence the transition from folded proteins to oligomeric aggregates.
• To elucidate the molecular mechanisms underlying membrane protein aggregation.

Main Methods:

• Developed a spectroscopic thermal perturbation method with 117 experimental variables.
• Utilized the Yersinia pestis outer transmembrane β-barrel Ail as a model system.
• Assessed the impact of single-residue substitutions on protein stability and aggregation.

Main Results:

• Identified that single-residue substitutions altering membrane-anchoring ability significantly impact protein kinetic stability.
• Observed a stabilizing role for interface aliphatics and a contribution of interface aromatics to self-assembly and aggregation.
• Detected the formation of structured oligomeric intermediates during protein aggregation.

Conclusions:

• Protein primary sequence variations critically influence aggregation propensity and stability.
• A thermodynamically compromised sequence balances folding, stability, and oligomerization to offset self-aggregation.
• The findings provide insights into the molecular progression of neurodegeneration and amyloidogenesis.