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Direct stimulus perception and transcription activation by a membrane‐bound DNA binding protein
Author(s) -
Gebhard Susanne,
Gaballa Ahmed,
Helmann John D.,
Cook Gregory M.
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06787.x
Subject(s) - biology , bacitracin , transmembrane protein , transcription (linguistics) , dna , regulon , transcription factor , dna binding protein , microbiology and biotechnology , biochemistry , gene , receptor , linguistics , philosophy , antibiotics
Summary Few membrane proteins with a role in transcriptional regulation have been studied, and none are able to perceive their respective stimuli and activate transcription of their regulons without the aid of auxiliary proteins. The bacitracin resistance regulator, BcrR, of Enterococcus faecalis is a membrane‐bound DNA binding protein and is required for bacitracin‐dependent expression of the bacitracin resistance genes, bcrABD . Here, we show that BcrR interacts directly with Zn 2+ bacitracin ( K d = 2–5 μM), but not metal‐free bacitracin. A solution‐based DNA binding assay demonstrated that the affinity of BcrR for its target DNA is much higher ( K d = 40 nM) than previously found for transmembrane regulators and is comparable to that of soluble DNA binding proteins. A construct of BcrR that lacked the transmembrane domain was unable to bind to DNA, indicating that membrane localization was important for DNA binding. Bacitracin did not cause a change in the DNaseI footprint of BcrR on the bcrA promoter, but in vitro transcription assays with BcrR proteoliposomes showed bacitracin‐dependent activation of transcription. These findings demonstrate that BcrR is a bona fide one‐component transmembrane signal transduction system, which perceives an extracellular stimulus (presence of bacitracin) and relays it to an intracellular transcriptional response independent of any auxiliary proteins.