Figure 6

Analysis of the role of the PAS domain of GabR in gabT transcription. Panel A, Domain organization of GabR. GabR is a Sigma 54-dependent activator that has three typical domains, the N-terminal regulatory domain (PAS domain, amino acids 22–119), the central AAA⁺ domain (amino acids 149–320) and C-terminal DNA-binding domain (HTH, amino acids 408–447). In the PAS domain deletion strain DPAS, the PAS domain from amino acids 33 to 128 is deleted from GabR. The gabR promoter region (606 bp) was used to construct the pHT1618-gabR and pHT1618-DPAS plasmids. Panel B, analysis of β-galactosidase activity induced from the gabT promoter in the Bt strain complemented with GabR or with the PAS deletion mutant in the presence or absence of GABA. Strain CgabR without (■), and with (●) 5 mM GABA, strain DPAS without (◊), and with (▲) 5 mM GABA. A₀ is mid-exponential phase (OD₆₀₀ = 1.0), and An is n hours after A₀.