Signaling mechanism of the transmembrane energy receptor Aer.

Cryo-EM structures of full-length Escherichia coli Aer show oxidized (kinase-on) versus reduced semiquinone (kinase-off) states reorganize the FAD pocket and destabilize the MHL-cap.

• Why it matters: Aer links cytoplasmic redox sensing to chemoreceptor signaling without MCP-like periplasmic ligand binding or adaptive methylation, leaving its lateral PAS-to-kinase mechanism unclear.
• What they did: The authors solved cryo-EM structures in oxidized flavin quinone and reduced semiquinone states, then used nanodisc reconstitution with pulse dipolar ESR on spin-labeled sites across the four-helix bundle.
• The result: Oxidation compresses the receptor and stabilizes proximal KCD helices via PAS-MHL-cap contacts, while reduction disrupts these interactions, loosening KCD packing—especially near the C-terminal MHL2 region.

AI summary of the abstract · may contain errors · not medical advice · read the paper.