Identification of a Malate Chemoreceptor in Pseudomonas aeruginosa by Screening for Chemotaxis Defects in an Energy Taxis-Deficient Mutant

ABSTRACT We found that a robust energy taxis response mediated by the Aer receptor can sometimes mask chemotaxis mediated by other methyl-accepting chemotaxis proteins (MCPs) in Pseudomonas aeruginosa. We identified PA2652 as a chemoreceptor for malate by screening aer mcp double mutants by using swarm plate assays.

Organization of the Aerotaxis Receptor Aer in the Membrane of Escherichia coli

ABSTRACT The Aer receptor guides Escherichia coli to specific oxygen and energy-generating niches. The input sensor in Aer is a flavin adenine dinucleotide-binding PAS domain, which is separated from a HAMP/signaling output domain by two membrane-spanning segments that flank a short (four-amino-acid) periplasmic loop. In this study, we determined the overall membrane organization of Aer by introducing combinations of residues that allowed us to differentiate intradimeric collisions from interdimeric collisions. Collisions between proximal residues in the membrane anchor were exclusively intra- or interdimeric but, with one exception, not both. Cross-linking profiles were consistent, with a rigid rather than flexible periplasmic loop and a tilted TM2 helix that crossed TM2′ at residue V197C, near the center of the lipid bilayer. The periplasmic loop formed a stable neighborhood that (i) included a maximum of three Aer dimers, (ii) did not swap neighbors over time, and (iii) appeared to be constrained by interactions in the cytosolic signaling domain.

The Aer Protein of Escherichia coli Forms a Homodimer Independent of the Signaling Domain and Flavin Adenine Dinucleotide Binding

ABSTRACT In vivo cross-linking between native cysteines in the Aer receptor of Escherichia coli showed dimer formation at the membrane anchor and in the putative HAMP domain. Dimers also formed in mutants that did not bind flavin adenine dinucleotide and in truncated peptides without a signaling domain and part of the HAMP domain.