Using experimental single-particle cryo-EM snapshots of ryanodine receptor (RyR1), a Ca2+-channel involved in skeletal muscle excitation/contraction coupling, we present quantitative free-energy landscapes, reaction coordinates, and three-dimensional movies of the continuous conformational changes associated with the binding of activating ligands. Our results show multiple routes to ligand binding with comparable branching ratios. All high-probability routes involve significant conformational changes before and after the binding of ligands. We also present new insights into the local structural changes along the ligand-binding route, including accommodations at the calcium, ATP, and caffeine binding sites. These observations shed new light on the mechanisms and conformational routes to ligand binding.

Conformational Dynamics and Energy Landscapes of Ligand Binding in RyR1