A dual role of the transcriptional regulator TstR provides insights into cyanide detoxification in Lactobacillus brevis. Issue 4 (14th April 2014)

• Record Type: Journal Article
• Authors: Pagliai, Fernando A.; Murdoch, Caitlin C.; Brown, Sara M.; Gonzalez, Claudio F.; Lorca, Graciela L.
• Is Part Of: Molecular microbiology. Volume 92:Issue 4(2014)
• Page Start: 853
• Page End: 871
• Publication Date: 2014-04-14
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.12598
• Languages: English
• ISSNs: 0950-382X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>In this study we uncover two genes in <italic>L</italic><italic>actobacillus brevis</italic> ATCC 367, <italic>tstT</italic> and <italic>tstR</italic>, encoding for a rhodanese and a transcriptional regulator involved in cyanide detoxification. TstT (LVIS_0852) belongs to a new class of thiosulphate:cyanide sulphurtransferases. We found that TstR (LVIS_0853) modulates both the expression and the activity of the downstream‐encoded <italic>tstT</italic>. The TstR binding site was identified at −1 to +33, from <italic>tstR</italic> transcriptional start site. EMSA revealed that sulphite, a product of the reaction catalysed by TstT, improved the interaction between TstR:<italic>P<sub>tstR</sub></italic>, while Fe(III) disrupted this interaction. Site‐directed mutagenesis in TstR identified M64 as a key residue in sulphite recognition, while residues H136‐H139‐C167‐M171 formed a pocket for ferric iron co‐ordination. In addition to its role as a transcriptional repressor, TstR is also involved in regulating the thiosulphate:cyanide sulphurtransferase activity of TstT. A threefold increase in TstT activity was observed in the presence of TstR, which was enhanced by the addition of Fe(III). Overexpression of the <italic>tstRT</italic> operon was found to increase the cyanide tolerance of <italic>L</italic><italic>. brevis</italic> and <italic>E</italic><italic>scherichia coli</italic>. The protein–protein interaction between TstR and TstT described herein represents a novel mechanism for regulation of enzymatic activity by a transcriptional regulator.</p> </abstract>