Computational Screening of Rhodopsin Mutations Associated with Retinitis Pigmentosa.

Area of Science:

• Biophysics
• Molecular Biology
• Genetics

Background:

• Retinitis pigmentosa (RP) is a group of hereditary disorders causing severe vision loss, affecting millions globally.
• Rhodopsin mutations are responsible for over 25% of autosomal dominant retinitis pigmentosa (ADRP) cases.
• ADRP-linked mutations often lead to impaired rhodopsin expression and function.

Purpose of the Study:

• To computationally screen 40 mutations in the second extracellular loop (EL2) of rhodopsin associated with ADRP.
• To understand the structural and dynamic effects of these mutations on rhodopsin's β-hairpin stability and folding.
• To correlate computational findings with in vitro experimental data on protein folding and expression.

Main Methods:

• Replica exchange molecular dynamics (REMD) simulations were employed.
• The FACTS implicit solvent model was utilized to study the free energy landscape of β-hairpin formation.
• A computational protocol was validated using the protein G C-terminal β-hairpin.

Main Results:

• Eight of the 40 EL2 mutants showed significant misfolding effects on the native β-hairpin structure, aligning with severe in vitro folding/expression defects.
• Five mutants exhibited moderate misfolding tendencies.
• Twenty-seven mutants had milder effects on rhodopsin expression, with minimal impact on β-hairpin conformation but potential disruption of chromophore interactions.

Conclusions:

• The study provides structural insights into the biochemical behavior of class II ADRP mutations.
• Computational screening effectively predicts misfolding and stability issues caused by specific rhodopsin mutations.
• Understanding these atomistic causes is crucial for developing therapeutic strategies for retinitis pigmentosa.