Rationalization of poor solubility of TGF-β3 using MD simulation

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Dynamics

Background:

• Transforming growth factor-beta 3 (TGF-β3) displays significantly lower solubility than other TGF-β isoforms, despite sequence and structural similarities.
• Understanding the molecular basis of TGF-β3's poor solubility is crucial for its therapeutic and research applications.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the poor solubility of TGF-β3 compared to TGF-β1.
• To identify structural differences contributing to the differential solubility of TGF-β isoforms.

Main Methods:

• Utilized nanosecond molecular dynamics (MD) simulations with explicit solvent for both TGF-β3 and TGF-β1.
• Simulations were conducted in the presence and absence of urea to probe unfolding intermediates.
• Analyzed changes in secondary structure, specifically α-helix and β-sheet content, and surface properties.

Main Results:

• MD simulations revealed an early loss of α-helix structure in TGF-β3 compared to TGF-β1.
• A specific fragment (H3 α-helix) of TGF-β3 showed a conversion to β-sheet structure during simulations.
• TGF-β3 exhibits hydrophobic patches on its surface and low charge across a wide pH range.

Conclusions:

• The relative instability of the H3 α-helix in TGF-β3 and its tendency to form β-sheet structures are key factors contributing to its poor solubility.
• Surface hydrophobicity and low overall charge further exacerbate the solubility issues of TGF-β3.
• These findings provide molecular insights into the differential solubility of TGF-β isoforms.