Structural analysis of the activation and DNA interactions of the response regulator VbrR from Vibrio parahaemolyticus

초록

VbrK and VbrR from the gastroenteritis-causing Vibrio parahaemolyticus are a histidine kinase and response regulator, respectively, that constitute a two-component regulatory system. VbrK responds to beta-lactam antibiotics or nitrate and activates VbrR via phosphorylation. Consequently, VbrR transcriptionally regulates the expression of beta-lactamase and ExsC and contributes to the survival or virulence of V. parahaemolyticus. Due to the unavailability of the VbrR structure, it remains unclear how VbrR is activated via its N-terminal receiver domain (RD) and recognizes dsDNA via its C-terminal DNA-binding domain (DBD). To reveal the mechanism underlying VbrR-mediated activation, we generated the phosphomimetic protein (VbrR(RD-D51E)) of the VbrR RD by replacing the D51 residue at the phosphorylation site with glutamate. VbrR(RD-D51E) exhibits a beta(7)alpha(5) structure rather than the typical beta(5)alpha(5) structure because it contains a unique two-stranded beta-sheet. The VbrR(RD-D51E) structure represents an active state in which the D51E residue interacts with the T78 residue. As a result, the Y97 residue adopts an inward conformation, allowing VbrR(RD-D51E) to dimerize using the alpha 4-beta 5-alpha 5 face. These activation events are facilitated by a VbrR-specific residue, R52. Further structural study demonstrated that the VbrR DBD adopts a beta-strand-decorated three-helix structure. Based on a comparative structural study, we propose that VbrR recognizes dsDNA by inserting the alpha 8 helix into the major groove of dsDNA and interacting with the minor groove of dsDNA via the beta 11-beta 12 region. Our findings will provide a new avenue for development of new antibacterial drugs for treating V. parahaemolyticus infections. (C) 2021 Elsevier Inc. All rights reserved.

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