Open AccessAgrobacterium tumefaciens estC, Encoding an Enzyme Containing Esterase Activity, Is Regulated by EstR, a Regulator in the MarR Family
Author(s) -
Surawach Rittiroongrad,
Nisanart Charoenlap,
Suparat Giengkam,
Paiboon Vattanaviboon,
Skorn Mongkolsuk
Publication year - 2016
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0168791
Subject(s) - repressor , gene , regulator , microbiology and biotechnology , transcription (linguistics) , biology , cumene hydroperoxide , regulator gene , transcriptional regulation , gene expression , chemistry , genetics , biochemistry , linguistics , philosophy , catalysis
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.