Figure 4. CorA adopts several highly dynamic conformations.

(a) Left: Surface representations of CorA cryo-EM structures in the high-resolution closed (PDB: 3JCF) and the two 7 Å resolution Mg²⁺-free open (PDBs 3JCH, 3JCG) conformations. Center: AFM topography simulations of the structures on the left. Right: Examples of HS-AFM frames of single CorA molecules in the symmetric closed (upper panel) and the asymmetric (putatively open) conformations (bottom panels). Full-frame size: 17.5 nm. Full z-scale: 2 nm. (b) High-resolution HS-AFM frames of an individual CorA channel upon Mg²⁺-depletion. The molecule fluctuates dynamically between several conformations. Time stamps are indicated. Full-frame size: 17.5 nm. Full z-scale: 2 nm. (c) HS-AFM image sequence of subsequent frames depicting CorA every 550 ms highlighting the structural flexibility of the molecule and the fast movements of the individual subunits. Full-frame size: 17.5 nm. Full z-scale: 2 nm. (d) HS-AFM image sequence depicting CorA every 250 ms. Full-frame size: 27 nm. Full z-scale: 2 nm.