Structural analyses of the AAA+ ATPase domain of the transcriptional regulator GtrR in the BDSF quorum sensing system in Burkholderia cenocepacia

GtrR is a key downstream regulator for quorum sensing signaling molecule cis-2-dodecenoic acid (BDSF). As a bacterial enhancer-binding protein (bEBP), GtrR is composed of an N-terminal receiver domain, a central AAA+ ATPase σ54 -interaction domain and a C-terminal helix-turn-helix DNA-binding domain. In this work, we solved its AAA+ ATPase domain in both apo and GTP-bound forms. The structure revealed how GtrR specifically recognizes GTP. In addition, we also revealed that GtrR has moderate GTPase activity in vitro in the absence of its activation signal. Finally, we found the residues K170, D236, R311 and R357 in GtrR that are crucial to its biological function, any single mutation leading to completely abolishing GtrR activity.