Real time dynamics of Gating-Related conformational changes in CorA

CorA, a divalent-selective channel in the metal ion transport superfamily, is the major Mg -influx pathway in prokaryotes. CorA structures in closed (Mg -bound), and open (Mg -free) states, together with functional data showed that Mg -influx inhibits further Mg -uptake completing a regulatory feedback loop. While the closed state structure is a symmetric pentamer, the open state displayed unexpected asymmetric architectures. Using high-speed atomic force microscopy (HS-AFM), we explored the Mg -dependent gating transition of single CorA channels: HS-AFM movies during Mg -depletion experiments revealed the channel's transition from a stable Mg -bound state over a highly mobile and dynamic state with fluctuating subunits to asymmetric structures with varying degree of protrusion heights from the membrane. Our data shows that at Mg -concentration below K , CorA adopts a dynamic (putatively open) state of multiple conformations that imply structural rearrangements through hinge-bending in TM1. We discuss how these structural dynamics define the functional behavior of this ligand-dependent channel.