8dik

Publication Abstract from PubMed

Bacterial chemotaxis results from coupling of chemoreceptor arrays to the CheA histidine kinase / CheY two-component system. The Per-Arnt-Sim (PAS) domain of the dimeric E coli aerotaxis receptor Aer monitors cellular respiration through a redox-sensitive FAD cofactor. Conformational shifts in the PAS domain instigated by the FADOX/ FADASQredox couple traverse the HAMP and KCD (Kinase Control Domain) of the Aer dimer to regulate CheA kinase activity. The native PAS domain of Aer is unstable in isolation and has not been previously purified. Here, residue substitutions that rescue FAD binding in an FAD binding-deficient full-length Aer variant were used in combination to stabilize the Aer PAS domain. We solved the 2.4 A resolution crystal structure of this variant, Aer-PAS-GVV, and revealed a PAS fold that contains distinct features associated with FAD-based redox sensing. These features include a close contact between the Arg115 side chain and N5 of the isoalloxazine ring and interactions of the flavin with the side chains of His53 and Asn85 that are poised to convey conformational signals from the cofactor to the protein surface. Additionally, we used redox dye equilibration coupled with a 5-deazariboflavin photocycle to determine the FADox/FADASQformal potentials of Aer-PAS-GVV and full-length Aer reconstituted into nanodiscs. The Aer redox couple is remarkably low at -289.6 +/- 0.4 mV vs SHE (Standard Hydrogen Electrode). In conclusion, we propose a model for Aer energy sensing based on the low potential Aer-PAS-FADox/FADASQcouple and the inability of Aer-PAS to bind to the fully-reduced FAD hydroquinone.

Redox properties and PAS domain structure of the E. coli Energy Sensor Aer indicate a multi-state sensing mechanism.,Maschmann ZA, Chua TK, Chandrasekaran S, Ibanez H, Crane BR J Biol Chem. 2022 Oct 14:102598. doi: 10.1016/j.jbc.2022.102598. PMID:36252616^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.