PhaQ, a New Class of Poly-β-Hydroxybutyrate (PHB)-Responsive Repressor, Regulates phaQ and phaP (Phasin) Expression in Bacillus megaterium through Interaction with PHB

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Abstract
Bacillus megaterium can produce poly-β-hydroxybutyrate (PHB) as carbon and energy storage materials. We now report that the phaQ gene, which is located upstream of the phasin-encoding phaP gene, codes for a new class of transcriptional regulator that negatively controls expression of both phaQ and phaP . A PhaQ binding site that plays a role in this control has been identified by gel mobility shift assays and DNase I footprinting analysis. We have also provided evidence that PhaQ could sense the presence of PHB in vivo and that artificial PHB granules could inhibit the formation of PhaQ-DNA complex in vitro by binding to PhaQ directly. These suggest that PhaQ is a PHB-responsive repressor.