Non-heme globin sensor domain of BA2291 histidine kinase and related domains
This subfamily includes the sensor domain of Bacillus anthracis BA2291 histidine kinase. BA2291 is one of the most active kinases in promoting sporulation, and is found in most members of the Bacillus cereus subfamily of the genus Bacillus, which includes B. anthracis and Bacillus thuringiensis, but not Bacillus subtilis. This subfamily also includes two sensor-only plasmid encoded sporulation inhibitors pXO1-118 and pXO2-61 found only in B. anthracis and various strains of Bacillus cereus having similar plasmids. The pXO1-118 and pXO2-61 sensor domains form homodimers, and in vitro bind fatty acid and halide, and not heme; there may be roles for fatty acid (or similar molecule), chloride ion, and possibly pH, as signaling cues. It has been proposed that BA2291 senses the same environmental cue in vivo, and that pXO1-118 and pXO2-61 act by titrating out an environmental signal that might cause an ill-timed sporulation.
Comment:A hydrophobic tunnel and hydrophilic chamber are occupied by a fatty acid, which engages a conserved arginine and chloride ion via its carboxyl head group.
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