ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
PL10. Specific Keys to Success for Ribozymes and Riboswitches: Metal Ions
and Metal Ion Complexes
R.K.O. Sigel
Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland,
e-mail: roland.sigel@aci.uzh.ch
RNAs are involved in many processes within living cells, ribozymes and riboswitches being only two examples
of functional RNAs. Ribozymes perform catalytic reactions, whereas riboswitches are involved in the regulation
of gene expression by specifically binding small metabolites. Our research focuses on the self-splicing group II
intron ribozyme Sc.ai5γ and two riboswitches responsive to either coenzyme B12 or Mg 2+ (Figure).
Like most group II introns, Sc.ai5γ is highly dependent on Mg 2+ and very sensitive to the presence of other M n+
ions [1]: Ca 2+ inhibits splicing already at very low concentrations. By a combination of biochemical [1b], NMR
[2] and single molecule FRET experiments [3] we are now investigating the origin of Ca 2+ inhibition by
characterizing the intrinsic metal ion binding properties of these large RNAs and the effect of different M n+ ions
on catalysis, local structures and folding.
The btuB riboswitch from E. coli regulates the expression of a B12 transport protein and thus the uptake of B12
into the cell. We could recently show that the corrin moiety is responsible for the structural change of the
riboswitch, whereas the axial ligands of B12 regulate the affinity towards the RNA [4]. We are currently
extending these studies by investigating the role of the corrin side chains on the riboswitch structure.
Acknowledgement: Financial support by the Swiss Nat. Sci. Found. (SNF-Förderungsprofessur PP002-114759
and project 200021-117999) is gratefully acknowledged.
References:
[1] a) R.K.O. Sigel, Eur. J. Inorg. Chem., 2281 (2005). b) M.C. Erat, R.K.O. Sigel, J. Biol. Inorg. Chem., 13, doi
10.1007/s00775-008-0390-7 (2008). c) E. Freisinger, R.K.O. Sigel, Coord. Chem. Rev., 251, 1834 (2007).
[2] a) M.C. Erat, O. Zerbe, T. Fox, R.K.O. Sigel, ChemBioChem, 8, 306 (2007). b) M.C. Erat, R.K.O. Sigel,
Inorg. Chem., 46, 11224 (2007).
[3] M. Steiner, D. Rueda, R.K.O. Sigel, submitted for publication.
[4] S. Gallo, M. Oberhuber, R.K.O. Sigel, B. Kräutler, ChemBioChem, 9, 1408 (2008).
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