A multifunctional gene (tetR) controls Tn10-encoded tetracycline resistance

Abstract

MATERIALS AND METHODS Chemicals and media. Tetracycline hydrochloride, isopropyl-13-D-thiogalactopyranoside, o-nitrophenyl-,B-D-galactopyranoside, and the protein molecular weight standards ovalbumin, a-chymotrypsinogen, and lysozyme were purchased from Sigma Chemical 633 on July 31, 2020 by guest

The McbR repressor modulated by the effector substanceS‐adenosylhomocysteine controls directly the transcription of a regulon involved in sulphur metabolism ofCorynebacterium glutamicumATCC 13032

“…Analysis of the amino acid sequence of the McbR protein already revealed a DNA binding domain characteristic for the TetR family of transcriptional regulators (Rey et al, 2003). All of the experimentally well-characterized members of this family such as TetR (Beck et al, 1982), ArcR (Ma et al, 1996) and MtrR; (Lucas et al, 1997) act as transcriptional repressors by binding to DNA in the absence of corresponding effector molecules. In the presence of the effector, the repressor protein can no longer bind to the operator sequence, enforcing its rapid dissociation from the DNA (Hillen et al, 1983).…”

Affinities of mAbs to Tet repressor complexed with operator or tetracycline suggest conformational changes associated with induction

“…Thirdly, a movement of dimerization helices A8, A10, A8′ and A10′ (a prime refers to the second unit of the dimer) could cause a rotation of both monomers against each other bringing the DNA recognition helices closer together. The epitopes of the mAbs used here are located in different functional domains (see Figs 1,5): 4F5 and Top19 recognize the DNA binding domain, 9F10 and 4G5 bind to A10 in the dimerization region and 7D5, 6G7, Tc14 and To32 recognize epitopes near the Tc-binding pocket. The locations of their epitopes make these mAbs suitable tools to investigate those conformational changes.…”

“…The Tn10 encoded class B determinant has been most intensively studied. Tc dependent regulation of resistance expression is mediated by the 23.3-kDa Tet repressor protein (TetR) on the level of transcription [5]. In the absence of Tc, TetR dimers bind to tandem operators (tetO1 and tetO2) of nearly identical sequences.…”

Tetracycline alters gene expression in Salmonella strains that harbor the Tn10 transposon

“…It harbors the Tn10 transposon, which confers resistance to tetracycline (Tc). Several aspects of the Tn10 biology have been thoroughly studied in the last decades, among them the mechanisms underlying Tc resistance (Beck et al, 1982;Smith and Bertrand, 1988;Aldema et al, 1996) and transposition regulation (Kleckner et al, 1996;Kennedy et al, 1998;Ross et al, 2013). In addition to transposition and Tc resistance specific determinants, Tn10 encodes several other genes, namely jemA, orf 2, 3, 4 (Chalmers et al, 2000), tetC and tetD (Braus et al, 1984) (Supporting Information Fig.…”