The importance of phosphorylation was supported by visualizing extensive interactions between the N- and C-terminal domains in the DevR structure that mask the DNA binding domain. A helix rearrangement mechanism was proposed to alleviate this inhibition. The present study was designed to understand the role of the Nand C-terminal domains in activation of the DevR regulon genes. We compared the DNA binding properties of DevRC and DevR and correlated the findings with their ability to activate gene expression. We show that DevRC activates albeit weakly, the aerobic expression of the DevR regulon. The inability of DevRC to support full induction is attributed, at least in part, to a failure to cooperatively recruit DevR to adjacently-placed secondary binding sites. We also show that devRC transcript and DevRC protein levels are not maintained during hypoxia. The present study reveals the multifunctional role of the DevRN domain. In addition to receiving the phosphosignal at Asp54 from DevS and DosT kinases, DevRN suppresses the DNA binding and transcription-activating ability of unphosphorylated DevR under aerobic conditions, sponsors cooperative binding of DevR with secondary binding sites, and it is required for sustaining DevR stability and autoregulation during hypoxia. Thus DevR action is mediated by both its N-terminal and C-terminal domains. Recently we showed by analyzing some target genes of the DevR regulon that robust induction depends on the binding of native phosphorylated DevR protein to two or more binding sites located in target promoters. A DevRC-DNA complex was visualized by others from crystal structure analysis, and therefore we hypothesized that perhaps DevRC could support robust aerobic expression of DevR regulon genes. To address this possibility, we characterised the isolated C-terminal domain of DevR with respect to its DNA binding properties in vitro and its role in transcriptional activation in vivo. In the present study, expression analysis suggests that DevRC does indeed support aerobic gene expression, but only at a modest level. An analysis of the arrangement of Dev boxes at target Gefitinib 184475-35-2 promoters and the pattern of their occupancy provides insights into the underlying defect. We show that DevRC does bind to DNA but it is not recruited to the adjacent binding site at a target promoter unlike intact DevR protein. This difference in binding property is crucial because we know that complete occupancy of the binding sites is functionally important for full induction. For example, DevRC does not bind to the S box in the tgs1-Rv3131 intergenic region and this defect is associated with the lack of Rv3131 aerobic expression. Taking together the results of previous and present findings, we attribute the poor aerobic induction of target genes, in fair measure, to the failure of DevRC to mediate cooperative interactions. The target promoters are characterized by an overlap of the TSP-proximal binding site with the -35 promoter element.