Direct Observation of Multiple Tautomers of Oxythiamine and their Recognition by the Thiamine Pyrophosphate Riboswitch
Name
Essigmann_Direct observation.pdf
Size
1.5 MB
Format
Adobe PDF
Checksum (MD5)
e421e561a0c3db36544f4bb83a560bda
Author(s)
Singh, Vipender
Peng, Chunte Sam
Li, Deyu
Mitra, Koyel
Silvestre, Katherine J.
Tokmakoff, Andrei
Essigmann, John M.
Date Issued
October 2013
Journal
ACS Chemical Biology
Publisher
American Chemical Society (ACS)
Citation
Singh, Vipender, Chunte Sam Peng, Deyu Li, Koyel Mitra, Katherine J. Silvestre, Andrei Tokmakoff, and John M. Essigmann. “Direct Observation of Multiple Tautomers of Oxythiamine and Their Recognition by the Thiamine Pyrophosphate Riboswitch.” ACS Chemical Biology 9, no. 1 (January 17, 2014): 227–36.
Version
Author's final manuscript
Abstract
Structural diversification of canonical nucleic acid bases and nucleotide analogues by tautomerism has been proposed to be a powerful on/off switching mechanism allowing regulation of many biological processes mediated by RNA enzymes and aptamers. Despite the suspected biological importance of tautomerism, attempts to observe minor tautomeric forms in nucleic acid or hybrid nucleic acid-ligand complexes have met with challenges due to the lack of sensitive methods. Here, a combination of spectroscopic, biochemical, and computational tools probed tautomerism in the context of an RNA aptamer-ligand complex; studies involved a model ligand, oxythiamine pyrophosphate (OxyTPP), bound to the thiamine pyrophosphate (TPP) riboswitch (an RNA aptamer) as well as its unbound nonphosphorylated form, oxythiamine (OxyT). OxyTPP, similarly to canonical heteroaromatic nucleic acid bases, has a pyrimidine ring that forms hydrogen bonding interactions with the riboswitch. Tautomerism was established using two-dimensional infrared (2D IR) spectroscopy, variable temperature FTIR and NMR spectroscopies, binding isotope effects (BIEs), and computational methods. All three possible tautomers of OxyT, including the minor enol tautomer, were directly identified, and their distributions were quantitated. In the bound form, BIE data suggested that OxyTPP existed as a 4′-keto tautomer that was likely protonated at the N1′-position. These results also provide a mechanistic framework for understanding the activation of riboswitch in response to deamination of the active form of vitamin B1 (or TPP). The combination of methods reported here revealing the fine details of tautomerism can be applied to other systems where the importance of tautomerism is suspected.
MIT Department
Massachusetts Institute of Technology. Center for Environmental Health Sciences
Massachusetts Institute of Technology. Department of Biological Engineering
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1021/cb400581f
