PMID: 22238377

Authors:

Palm GJ, Khanh Chi B, Waack P, Gronau K, Becher D, Albrecht D, Hinrichs W, Read RJ, Antelmann H

Title:

Structural insights into the redox-switch mechanism of the MarR/DUF24-type regulator HypR.

Journal:

Nucleic Acids Res. 2012 May 1;40(9):4178-92. Epub 2012 Jan 11.

Abstract:

Bacillus subtilis encodes redox-sensing MarR-type regulators of the OhrR and DUF24-families that sense organic hydroperoxides, diamide, quinones or aldehydes via thiol-based redox-switches. In this article, we characterize the novel redox-sensing MarR/DUF24-family regulator HypR (YybR) that is activated by disulphide stress caused by diamide and NaOCl in B. subtilis. HypR controls positively a flavin oxidoreductase HypO that confers protection against NaOCl stress. The conserved N-terminal Cys14 residue of HypR has a lower pK(a) of 6.36 and is essential for activation of hypO transcription by disulphide stress. HypR resembles a 2-Cys-type regulator that is activated by Cys14-Cys49' intersubunit disulphide formation. The crystal structures of reduced and oxidized HypR proteins were resolved revealing structural changes of HypR upon oxidation. In reduced HypR a hydrogen-bonding network stabilizes the reactive Cys14 thiolate that is 8-9 A apart from Cys49'. HypR oxidation breaks these H-bonds, reorients the monomers and moves the major groove recognition alpha4 and alpha4' helices approximately 4 A towards each other. This is the first crystal structure of a redox-sensing MarR/DUF24 family protein in bacteria that is activated by NaOCl stress. Since hypochloric acid is released by activated macrophages, related HypR-like regulators could function to protect pathogens against the host immune defense.