Recent Papers

The nag genes are an operon in Ralstonia sp. strain U2 that is regulated by NagR, a LysR-type transcriptional regulator.Jones, R.M., Britt-Compton B. & Williams P.A.  J. Bacteriol. (Submitted)

ABSTRACT

In Ralstonia sp. strain U2, the nag catabolic genes which encode the enzymes for the pathway that catabolize naphthalene via the alternative ring-cleavage gentisate pathway are transcribed as an operon under the same promoter. Divergently transcribed to the nag catabolic genes is nagR, which encodes a LysR-type transcriptional regulator. A 4 bp frameshift deletion in nagR demonstrated that NagR is required for the expression of the nag operon. The transcriptional start of the nag operon was mapped, and a putative -10, -35 sigma 70-type promoter binding site was identified. Further upstream, a site proximal to the promoter was identified as having bases which have been found to be conserved in the LysR-type activator-binding motif. Transcriptional fusion studies demonstrated that NagR regulates the expression of the nag operon positively in the presence of salicylate, and to a lesser extent in the presence of 2-nitrobenzoate. Mutation of the LysR-type activator-binding motif in the nag promoter-proximal region,  resulted in loss of inducibility of a LacZ reporter gene transcriptionally fused the nagAa, the first gene of the operon. However other mutations within the region produced elevated levels of  nag gene expression even in the presence of the inducer salicylate.