title: Delineating PAS-HAMP interaction surfaces and signalling-associated changes in the aerotaxis receptor Aer.
abstract: 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. We mapped the interaction surfaces of the Aer PAS, HAMP and proximal signalling domains in the kinase-off state by probing the solvent accessibility of 129 cysteine substitutions. Inaccessible PAS-HAMP surfaces overlapped with a cluster of PAS kinase-on lesions and with cysteine substitutions that crosslinked the PAS β-scaffold to the HAMP AS-2 helix. A refined Aer PAS-HAMP interaction model is presented. Compared to the kinase-off state, the kinase-on state increased the accessibility of HAMP residues (apparently relaxing PAS-HAMP interactions), but decreased the accessibility of proximal signalling domain residues. These data are consistent with an alternating static-dynamic model in which oxidized Aer-PAS interacts directly with HAMP AS-2, enforcing a static HAMP domain that in turn promotes a dynamic proximal signalling domain, resulting in a kinase-off output. When PAS-FAD is reduced, PAS interaction with HAMP is relaxed and a dynamic HAMP and static proximal signalling domain convey a kinase-on output.
authors.affiliation: Division of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, CA, 92350, USA.
authors.forename: Darysbel
authors.initials: D
authors.lastname: Garcia
authors.affiliation: Division of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, CA, 92350, USA.
authors.forename: Kylie J
authors.initials: KJ
authors.lastname: Watts
authors.affiliation: Division of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, CA, 92350, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.affiliation: Division of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, CA, 92350, USA.
authors.forename: Barry L
authors.initials: BL
authors.lastname: Taylor
mesh_terms: D000596:Amino Acids; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D004220:Disulfides / Q000737:chemistry; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D015398:Signal Transduction
chemical_list: D000596:Amino Acids; D002352:Carrier Proteins; D004220:Disulfides