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PAS/poly‐HAMP signalling in Aer‐2, a soluble haem‐based sensor
Author(s) -
Watts Kylie J.,
Taylor Barry L.,
Johnson Mark S.
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07477.x
Subject(s) - hamp , hamp domain , biology , biochemistry , microbiology and biotechnology , chemotaxis , kinase , receptor , immunology , binding site , binding domain , inflammation , hepcidin
Summary Poly‐HAMP domains are widespread in bacterial chemoreceptors, but previous studies have focused on receptors with single HAMP domains. The Pseudomonas aeruginosa chemoreceptor, Aer‐2, has an unusual domain architecture consisting of a PAS‐sensing domain sandwiched between three N‐terminal and two C‐terminal HAMP domains, followed by a conserved kinase control module. The structure of the N‐terminal HAMP domains was recently solved, making Aer‐2 the first protein with resolved poly‐HAMP structure. The role of Aer‐2 in P. aeruginosa is unclear, but here we show that Aer‐2 can interact with the chemotaxis system of Escherichia coli to mediate repellent responses to oxygen, carbon monoxide and nitric oxide. Using this model system to investigate signalling and poly‐HAMP function, we determined that the Aer‐2 PAS domain binds penta‐co‐ordinated b ‐type haem and that reversible signalling requires four of the five HAMP domains. Deleting HAMP 2 and/or 3 resulted in a kinase‐off phenotype, whereas deleting HAMP 4 and/or 5 resulted in a kinase‐on phenotype. Overall, these data support a model in which ligand‐bound Aer‐2 PAS and HAMP 2 and 3 act together to relieve inhibition of the kinase control module by HAMP 4 and 5, resulting in the kinase‐on state of the Aer‐2 receptor.