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Title: Mn 2+-Sensing Mechanisms of yybP-ykoY Orphan Riboswitches

Gene regulation in cis by riboswitches is prevalent in bacteria. The yybP-ykoY riboswitch family is quite widespread, yet its ligand and function remained unknown. Here in this paper, we characterize the Lactococcus lactis yybP-ykoY orphan riboswitch as a Mn2+-dependent transcription-ON riboswitch, with a ~30–40 μM affinity for Mn 2+. We further determined its crystal structure at 2.7 Å to elucidate the metal sensing mechanism. The riboswitch resembles a hairpin, with two coaxially stacked helices tethered by a four-way junction and a tertiary docking interface. The Mn 2+-sensing region, strategically located at the highly conserved docking interface, has two metal binding sites. Whereas one site tolerates the binding of either Mg 2+ or Mn 2+, the other site strongly prefers Mn 2+ due to a direct contact from the N7 of an invariable adenosine. Lastly, mutagenesis and a Mn 2+-free E. coli yybP-ykoY structure further reveal that Mn 2+ binding is coupled with stabilization of the Mn2+-sensing region and the aptamer domain.
 [1] ;  [2] ;  [1] ;  [2] ;  [1]
  1. Cornell Univ., Ithaca, NY (United States). Dept. of Molecular Biology and Genetics
  2. Cornell Univ., Ithaca, NY (United States). Dept. of Microbiology
Publication Date:
OSTI Identifier:
Grant/Contract Number:
GM086766; GM102543; GM059323; RR15301; W31-109-ENG-38; GM103485; DMR-0936384
Published Article
Journal Name:
Molecular Cell
Additional Journal Information:
Journal Volume: 57; Journal Issue: 6; Journal ID: ISSN 1097-2765
Elsevier - Cell Press
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States