The structural basis of the response regulator DrRRA from Deinococcus radiodurans

DrRRA, a vital and recently discovered gene product of Deinococcus radiodurans, is a member of the OmpR/PhoB family of response regulators that couple with the cognate histidine kinase (HK) to form a typical two component system (TCS). It is known that the DrRRA is responsible for the transcriptional levels of numerous genes mostly relating to the stress response and DNA repair. In this paper, the crystal structures of the effector domain and full-length protein of DrRRA with resolutions of 1.6 and 2.3 Å, respectively, are determined. These crystal structures depicted that DrRRA has the structural features of the OmpR/PhoB subfamily and were also confirmed by SAXS investigation of the protein in solution. Our data suggest that the receiver domain blocks the binding of DNA to the DNA recognition helix of effector domain; while the interdomain interface would be unwrapped, via the phosphorylation of receiver domain and/or the inducement of DNA, in order to provide DNA binding.

► Crystal structures of the DrRRA and the effector domain are analyzed.
► SAXS on the conformation in solution of DrRRA confirmed the structure.
► Data suggest that the N-ter domain blocks the DNA binding to the effector domain.
► Wrapped interdomain interface inhibits the DNA binding and stabilization.