Structural and Dynamic Perturbations in the RyR1 Selectivity Filter Induced by Ala4893 Mutations: Implications for Malignant Hyperthermia and Myopathy.

Mutations at Ala4893 within the selectivity filter (SF) of ryanodine receptor 1 (RyR1) are associated with distinct clinical phenotypes, including malignant hyperthermia (MH) and congenital myopathy. Here, we employed atomistic molecular dynamics simulations to examine how four Ala4893 variants (A4893T, A4893S, A4893P, and A4893G) influence the structure, dynamics, and energetic features of the RyR1 pore domain. The A4893T mutation is associated with an expanded SF geometry, increased local flexibility, enhanced intra-subunit hydrogen bonding, and reduced inter-subunit coupling, features that are consistent with a destabilized pore architecture. In contrast, A4893P favors pore compaction and backbone rigidification, accompanied by strengthened inter-subunit salt bridges, indicative of a more constrained pore ensemble. The A4893S and A4893G variants display intermediate behavior, characterized by variant-specific shifts in backbone dihedral distributions and hydrogen-bonding networks. Dynamic cross-correlation analyses further reveal mutation-dependent changes in coordinated motions across the S5 helix, selectivity filter, and S6 segment. Together, these results provide atomistic insight into how substitutions at Ala4893 reshape the structural and dynamic landscape of the RyR1 selectivity filter and offer a mechanistic framework for interpreting mutation-dependent functional outcomes reported experimentally.