Replica Exchange Molecular Dynamics Simulations Reveal Self-association Sites in M- Crystallin Caused by Mutations Provide Insights of Cataract

Crystallins are ubiquitous, however, prevalence is seen in eye lens. Eye lens crystallins are long-lived and structural intactness is required for maintaining lens transparency and protein solubility. Mutations in crystallin often lead to cataract. In this study, we performed mutations at specific sites of M-crystallin, a close homologue of eye lens crystallin and studied by employing replica exchange molecular dynamics with generalized Born solvation model. Mutations were made on the Ca 2+ binding residues (K34D and S77D) and in the hydrophobic core (W45R) which is known to cause congenital cataract in homologous γD-crystallin. The chosen mutations caused large motion of the N-terminal Greek key, concomitantly break the interlocking Greek keys interactions and perturbed the compact core resulting in several folded and partially unfolded states. Partially unfolded states expose large hydrophobic patches that can act as precursors for self-aggregation. Accumulation of such aggregates is the potential cause of cataract in homologous crystallins.