Phosphorylation as a tool to modulate aggregation propensity and to predict fibril architecture

Area of Science:

• Biochemistry
• Biophysics
• Materials Science

Background:

• Post-translational modifications impact protein and peptide solubility and conformation.
• The precise influence of chemical modifications on peptide aggregation propensity is not fully understood.

Purpose of the Study:

• To investigate the effect of phosphorylation on the aggregation propensity of a synthetic peptide.
• To determine how pH influences phosphorylation's effect on peptide aggregation.

Main Methods:

• Synthesized a 13-residue peptide with phosphorylation at seven distinct sites.
• Analyzed fibril formation at various pH values (1.1, 3.6, and 7.5).
• Utilized molecular dynamics (MD) simulations to model peptide behavior and predict fibril structures.

Main Results:

• Fibril formation was inhibited at pH 7.5 (fully charged phosphate) but rapid at pH 1.1 (protonated phosphate).
• At pH 3.6 (mono-anionic phosphate), aggregation depended heavily on phosphate group position.
• MD simulations supported the formation of class 7 amyloid fibrils.

Conclusions:

• Phosphorylation offers a reversible method to control peptide aggregation kinetics.
• Exploiting pH-dependent charge states of phosphate groups allows prediction and rationalization of aggregation behavior.
• Combined experimental and computational approaches can predict fibril structures and their pH sensitivity.