Mutation effects on FAS1 domain 4 based on structure and solubility

Area of Science:

• Biochemistry
• Molecular Biology
• Ophthalmology

Background:

• Mutations in the fasciclin 1 domain 4 (FAS1-4) of transforming growth factor β-induced protein (TGFBIp) are linked to corneal dystrophies (CDs).
• The reduced solubility of mutated TGFBIp is implicated in CD pathogenesis.
• The precise molecular mechanisms underlying this solubility decrease remain unclear.

Purpose of the Study:

• To investigate the molecular mechanisms behind the decreased solubility of mutated TGFBIp.
• To analyze the structural and thermodynamic changes in FAS1-4 domain mutants using molecular dynamics simulations.
• To establish a link between specific mutations and conformational alterations affecting protein solubility.

Main Methods:

• Molecular dynamics simulations were employed to study the wild-type FAS1-4 domain and three specific mutants (R555W, R555Q, A546T).
• Solvation thermodynamic analyses were performed to quantify the changes in protein-water interactions.
• Structural analysis focused on identifying conformational changes and altered intermolecular interactions near mutation sites.

Main Results:

• Both R555W and R555Q mutants exhibited reduced affinity for water compared to the wild-type protein.
• The R555W mutation led to increased solvation free energy due to hydrophobic burial of W555 and salt bridge formation involving R557.
• The R555Q mutation also increased solvation free energy, driven by structural rearrangements distant from the mutation site, involving R558 forming multiple salt bridges.

Conclusions:

• The study identifies a direct correlation between specific mutations in the TGFBIp FAS1-4 domain and decreased protein solubility.
• Conformational changes, including altered hydrophobic interactions and salt bridge formations, are key drivers of reduced solubility.
• These findings provide insights for developing therapeutics to inhibit FAS1 aggregation in corneal dystrophies.