The Site-Directed A184S Mutation in the HTH Domain of the Global Regulator IrrE Enhances Deinococcus radiodurans R1 Tolerance to UV Radiation and MMC Shock

Abstract

IrrE is a highly conserved global regulator in the Deinococcus genus and contributes to survival from high doses of UV radiation, ionizing radiation, and desiccation. Drad-IrrE and Dgob-IrrE from Deinococcus radiodurans and Deinococcus gobiensis I-0 each share 66% sequence identity. However, Dgob-IrrE showed a stronger protection phenotype against UV radiation than Drad- IrrE in the D. radiodurans irrE-deletion mutant (ΔirrE), which may be due to amino acid residues differences around the DNA-binding HTH domain. Site-directed mutagenesis was used to generate a Drad-IrrE A184S single mutant, which has been characterized and compared with the ΔirrE mutant complemented strain with Drad-irrE, designated ΔirrE-E. The effects of the A184S mutation following UV radiation and mitomycin C (MMC) shock were determined. The A184S mutant displayed significantly increased resistance to UV radiation and MMC shock. The corresponding A184 site in Dgob-IrrE was inversely mutated, generating the S131A mutant, which exhibited a loss of resistance against UV radiation, MMC shock, and desiccation. qPCR analysis revealed that critical genes in the DNA repair system, such as recA, pprA, uvrA, and ddrB, were remarkably induced after UV radiation and MMC shock in the ΔirrE-IE and A184S mutants. These data suggested that A184S improves the ability against UV radiation and MMC shock, providing new insights into the modification of IrrE. We speculated that the serine residue may determine the efficiency of DNA binding, leading to the increased expression of IrrE-dependent genes important for protection against DNA damage.

Improving Biotransformation Efficiency of Arthrobacter simplex by Enhancement of Cell Stress Tolerance and Enzyme Activity

“…deserti IrrE . Impressively, all mutation sites distinctly differed from those of variants reported previously. ,,, …”

“…By relieving cellular oxidative damage, IrrE also conferred E. coli tolerance to ethanol and methanol , or salt stress, , P. aeruginosa tolerance to alkaline conditions or salt stress, and S.…”

“…29 Impressively, all mutation sites distinctly differed from those of variants reported previously. 12,16,29,45 The local conformational changes of four mutation sites were analyzed (Figure 5C and Figure S7). Compared with R111, 111H could form a new hydrogen bond with the arginine residue at the C108 position (Figure 5C), which is present in the core region of the dimer interface based on the sequence alignment with D. deserti IrrE and strictly conserved in Deinococcus IrrE.…”

A tamB homolog is involved in maintenance of cell envelope integrity and stress resistance of Deinococcus radiodurans

“…To date, more than 50 species of the Deinococcus genus have been identified in a variety of environments18. Deinococcus are distinguished by their extraordinary tolerance to a number of lethal agents including ionizing radiation, hydrogen peroxide, osmotic pressure, desiccation, UV radiation and mitomycin C (MMC)19202122. It is widely accepted that efficient DNA repair systems and cell defence systems including an unusual cell envelope and small molecule antioxidants (e.g.…”

DrwH, a novel WHy domain-containing hydrophobic LEA5C protein from Deinococcus radiodurans, protects enzymatic activity under oxidative stress

“…To determine whether drwH is regulated by IrrE, we checked the expression levels of drwH in the D . radiodurans Δ irrE mutant strain previously constructed 33 . As shown in Fig.…”