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

Abstract

Summary 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.

Identification of a Chemoreceptor in Pseudomonas aeruginosa That Specifically Mediates Chemotaxis Toward α-Ketoglutarate

“…In particular its responses to amino acids by the three paralogous receptors PctA, PctB, and PctC (Kuroda et al, 1995; Taguchi et al, 1997; Rico-Jimenez et al, 2013; McKellar et al, 2015; Reyes-Darias et al, 2015a,b) as well as its response to inorganic phosphate (Wu et al, 2000; Rico-Jimenez et al, 2016) by the CtpL and CtpH receptors have been studied in some depth. In addition, the cytosolic and atypical receptor McpB (also named Aer2) (Watts et al, 2011; Airola et al, 2013; Garcia-Fontana et al, 2014; Garcia et al, 2016) was subject to many studies and is amongst the best studied members of the chemoreceptor sub-family with cytoplasmic location. Chemoreceptor PA2652 was identified as a specific malate chemoreceptor (Alvarez-Ortega and Harwood, 2007) and TlpQ responsible for the chemotaxis toward the plant hormone ethylene (Kim et al, 2007).…”

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

“…1a) (14). This contrasts with the aerotaxis receptor, Aer, where side-on PAS-HAMP interactions allow PAS to control the HAMP signaling state through direct interactions (17). For Aer2, several structures have been solved for the N-terminal HAMP domains (18,19).…”

Phylogenetic Characterization of the Energy-taxis Receptor Aer inPseudomonasand Phenotypic Characterization inP. pseudoalcaligenesKF707

“…Interestingly, it was the cytoplasmic region between the transmembrane helices and kinase control domain where a HAMP domain was expected that differed most between groups (Figure 3). In Aer from E. coli the HAMP domain in this region [42] interacts with the PAS domain and is essential for the function of the protein as the HAMP domain transfers the signal through the protein [11]. The motif (5)RP[…]DEXG(36) is representative of ‘canonical’ HAMP domains where the signal is transduced through the membrane [31], but was only found in Aer.g2.…”

“…This was also named ‘Aer2’ so we will refer to the cytosolic receptor Aer-2 as McpB hereafter. It has been shown to bind oxygen, but does not affect flagellar activity as it is key to the assembly of, and signals through the Che2 chemosensory system (whose function is unknown) [11–13].…”