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. 2024 Oct 17;7:1345. doi: 10.1038/s42003-024-07008-5

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© The Author(s) 2024

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 1 — a The tbpA riboswitch controls the expression of the tbpA-thiP-thiQ operon that is involved in the transport of thiamin and related metabolites. The riboswitch is located in the 5’ untranslated region and adopts the ON state in the absence of TPP in which the anti-P1 stem is formed, thereby allowing the initiation of translation. However, in the presence of TPP, the OFF state is adopted in which the P1 stem of the aptamer domain is stabilized, therefore repressing translation initiation. The GUG start codon is shown in blue. b Secondary structure of the tbpA riboswitch in the TPP-bound OFF structure. The anti-P1 stem is highlighted in yellow and the P1 stem is circled in blue. The Shine-Dalgarno and GUG start codon are shown in blue. c Schematics depicting the constructs used for ß-galactosidase assays. All fusions contain the natural promoter. The “- fusion” represents the construct in which the riboswitch domain is not present. The translational fusion (TrL) contains 11 codons of tbpA and is directly fused to the lacZ reporter. The transcriptional fusion (TrX) contains an additional Shine-Dalgarno (SD) sequence that allows the translation of the lacZ reporter without being affected by the structure of the riboswitch. d ß-galactosidase assays for the promoter-only (-), translational (TrL) and transcriptional (TrX) fusions. The average values of three independent experiments with standard deviations are shown. ß-galactosidase assays for constructs expressed from an arabinose-inducible promoter (pBAD). Gene expression was assessed for the wild-type (WT), G35C, G121C and U130A constructs in the context of both the translational (TrL) (e) and transcriptional (TrX) (f) fusions. The average values of three independent experiments with standard deviations are shown.