Folding nucleus structure persists in thermally-aggregated FGF-1

Area of Science:

• Biochemistry
• Structural Biology
• Protein Dynamics

Background:

• Efficient protein folding and aggregation avoidance are critical for protein evolution and de novo design.
• The specific design principles for achieving efficient folding and preventing aggregation remain poorly understood.

Purpose of the Study:

• To characterize the thermally-induced aggregate of fibroblast growth factor-1 (FGF-1) using solid-state NMR.
• To elucidate the structural and dynamic properties of aggregated FGF-1 and their relationship to the folding pathway.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze the thermally-induced aggregate of FGF-1.
• Comparative analysis with a designed protein variant was performed to validate findings.

Main Results:

• NMR data revealed residual structure in the FGF-1 aggregate, corresponding to the folding nucleus.
• Unstructured regions with hydration-dependent dynamics were identified outside the folding nucleus.
• These unstructured regions are postulated to unfold early, leading to aggregation.

Conclusions:

• The study suggests that the folding nucleus and aggregation avoidance are potentially separable design criteria in protein engineering.
• Physicochemical properties of regions outside the folding nucleus are crucial for preventing aggregation.
• This work provides insights into designing proteins with efficient folding and reduced aggregation propensity.