Agrobacterium tumefaciens estC, Encoding an Enzyme Containing Esterase Activity, Is Regulated by EstR, a Regulator in the MarR Family

PLoS One. 2016 Dec 30;11(12):e0168791. doi: 10.1371/journal.pone.0168791. eCollection 2016.

Abstract

Analysis of the A. tumefaciens genome revealed estC, which encodes an esterase located next to its transcriptional regulator estR, a regulator of esterase in the MarR family. Inactivation of estC results in a small increase in the resistance to organic hydroperoxides, whereas a high level of expression of estC from an expression vector leads to a reduction in the resistance to organic hydroperoxides and menadione. The estC gene is transcribed divergently from its regulator, estR. Expression analysis showed that only high concentrations of cumene hydroperoxide (CHP, 1 mM) induced expression of both genes in an EstR-dependent manner. The EstR protein acts as a CHP sensor and a transcriptional repressor of both genes. EstR specifically binds to the operator sites OI and OII overlapping the promoter elements of estC and estR. This binding is responsible for transcription repression of both genes. Exposure to organic hydroperoxide results in oxidation of the sensing cysteine (Cys16) residue of EstR, leading to a release of the oxidized repressor from the operator sites, thereby allowing transcription and high levels of expression of both genes. The estC is the first organic hydroperoxide-inducible esterase-encoding gene in alphaproteobacteria.

MeSH terms

  • Agrobacterium tumefaciens / genetics*
  • Agrobacterium tumefaciens / metabolism
  • Amino Acid Sequence
  • Bacterial Proteins / genetics*
  • Esterases / genetics*
  • Gene Expression Regulation, Bacterial / genetics
  • Hydrogen Peroxide / metabolism
  • Oxidation-Reduction
  • Promoter Regions, Genetic
  • Repressor Proteins / genetics
  • Sequence Alignment
  • Transcription Factors / genetics

Substances

  • Bacterial Proteins
  • Repressor Proteins
  • Transcription Factors
  • Hydrogen Peroxide
  • Esterases

Grants and funding

This work was supported by grants from the Chulabhorn Research Institute, Mahidol University, and the Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Thailand (EHT-R 1/2556-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.