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The Aer2 receptor from Vibrio cholerae is a dual PAS‐heme oxygen sensor
Author(s) -
GreerPhillips Suzanne E.,
Sukomon Nattakan,
Chua Teck Khiang,
Johnson Mark S.,
Crane Brian R.,
Watts Kylie J.
Publication year - 2018
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/mmi.13978
Subject(s) - vibrio cholerae , biology , heme , pas domain , receptor , chemotaxis , ligand (biochemistry) , biochemistry , microbiology and biotechnology , bacteria , genetics , gene , enzyme , transcription factor
Summary The diarrheal pathogen Vibrio cholerae navigates complex environments using three chemosensory systems and 44–45 chemoreceptors. Chemosensory cluster II modulates chemotaxis, whereas clusters I and III have unknown functions. Ligands have been identified for only five V. cholerae chemoreceptors. Here, we report that the cluster III receptor, Vc Aer2, binds and responds to O 2 . Vc Aer2 is an ortholog of Pseudomonas aeruginosa Aer2 ( Pa Aer2) but differs in that Vc Aer2 has two, rather than one, N‐terminal PAS domain. We have determined that both PAS1 and PAS2 form homodimers and bind penta‐coordinate b ‐type heme via an Eη‐His residue. Heme binding to PAS1 required the entire PAS core, but receptor function also required the N‐terminal cap. PAS2 functioned as an O 2 ‐sensor [K d( O 2 ), 19 μM], utilizing the same Iβ Trp (W276) as Pa Aer2 to stabilize O 2 . The crystal structure of PAS2‐W276L was similar to that of Pa Aer2‐PAS but resided in an active conformation mimicking the ligand‐bound state, consistent with its signal‐on phenotype. PAS1 also bound O 2 [K d( O 2 ), 12 μM], although O 2 binding was stabilized by either a Trp residue or Tyr residue. Moreover, PAS1 appeared to function as a signal modulator, regulating O 2 ‐mediated signaling from PAS2 and resulting in activation of the cluster III chemosensory pathway.