Repression of bacterial gene expression by antivitamin B12binding to a cobalamin riboswitch

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Widner, Florian J., Khan, Naziyat I., Deery, Evelyne, Warren, Martin J., Taga, Michiko E. and Kräutler, Bernhard (2026) Repression of bacterial gene expression by antivitamin B12binding to a cobalamin riboswitch. RSC Chemical Biology, 7 (3). pp. 498-504. ISSN 2633-0679

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Abstract

The E. coli btuB riboswitch is a cobalamin-sensing RNA element that selectively binds coenzyme B12 (adenosylcobalamin, AdoCbl) to downregulate the expression of the outer membrane B12-transporter BtuB. Here, we examined adenosylrhodibalamin (AdoRhbl), the isostructural Rh-analogue of AdoCbl, as a surrogate effector ligand for this riboswitch. Two riboswitch-reporter systems were employed: an engineered E. coli strain with a fluorescent reporter for intracellular AdoCbl-sensing, and a plasmid-based construct for analogous in vitro transcription/translation assays. In the in-vitro system AdoRhbl closely mimicked AdoCbl in down-regulating reporter expression with apparent EC50 values of 2.8 µM and 0.8 µM respectively. In contrast, the engineered E. coli strain revealed much higher effective sensitivities, with EC50 values of 1.4 nM for AdoRhbl and of 6.9 nM for AdoCbl, reflecting strong intracellular accumulation of both corrinoids, and comparably efficient uptake. These findings uncover a previously undocumented gene-regulatory activity of an antivitamin, suggesting that AdoRhbl can repress bacterial B12 uptake by binding to the btuB riboswitch. Together with its ability to inhibit AdoCbl-dependent enzymes, the designed antivitamin B12AdoRhbl thus emerges as a multifunctional antibiotic candidate targeting B12-utilizing microorganisms.

Item Type: Article
Additional Information: Data availability: The data supporting this article have been included in the supplementary information (SI). Supplementary information is available. See DOI: https://doi.org/10.1039/d5cb00308c.
Uncontrolled Keywords: chemistry (miscellaneous),biochemistry,molecular biology,biochemistry, genetics and molecular biology (miscellaneous) ,/dk/atira/pure/subjectarea/asjc/1600/1601
Faculty \ School: Faculty of Science
UEA Research Groups: Faculty of Medicine and Health Sciences > Research Centres > Norwich Institute for Healthy Aging
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Depositing User: LivePure Connector
Date Deposited: 13 May 2026 15:47
Last Modified: 14 May 2026 15:16
URI: https://ueaeprints.uea.ac.uk/id/eprint/103013
DOI: 10.1039/d5cb00308c

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