Gas Sensing and Signaling in the PAS-Heme Domain of the Pseudomonas aeruginosa Aer2 Receptor.

The Aer2 chemoreceptor from contains a PAS sensing domain that coordinates -type heme and signals in response to the binding of O, CO, or NO. PAS-heme structures suggest that Aer2 uniquely coordinates heme via a His residue on a 3 helix (H234 on Eη), stabilizes O binding via a Trp residue (W283), and signals via both W283 and an adjacent Leu residue (L264). Ligand binding may displace L264 and reorient W283 for hydrogen bonding to the ligand.

Delineating PAS-HAMP interaction surfaces and signalling-associated changes in the aerotaxis receptor Aer.

The Escherichia coli aerotaxis receptor, Aer, monitors cellular oxygen and redox potential via FAD bound to a cytosolic PAS domain. Here, we show that Aer-PAS controls aerotaxis through direct, lateral interactions with a HAMP domain. This contrasts with most chemoreceptors where signals propagate along the protein backbone from an N-terminal sensor to HAMP.