Roland K. O. Sigel

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Group II intron ribozymes fold into their native structure by a unique stepwise process that involves an initial slow compaction followed by fast formation of the native state in a Mg(2+)-dependent manner. Single-molecule fluorescence reveals three distinct on-pathway conformations in dynamic equilibrium connected by relatively small activation barriers.(More)
The phosphate–sugar backbone of RNA and DNA imposes a large negative charge that needs to be neutralized for threedimensional structure assembly. In addition to proteins and polyamines, the most important cofactors that bind nucleic acids are metal ions. They help to overcome repulsion forces and mediate the formation of higher order structures. Metal ions(More)
Mg(2+) has been shown to modulate the function of riboswitches by facilitating the ligand-riboswitch interactions. The btuB riboswitch from Escherichia coli undergoes a conformational change upon binding to its ligand, coenzyme B12 (adenosyl-cobalamine, AdoCbl), and down-regulates the expression of the B12 transporter protein BtuB in order to control the(More)
Volume 8, solely devoted to the toxicology of metals and metalloids as well as their compounds, focuses on human health. Not surprisingly, all related research areas are rapidly developing due to the role of metals and metalloids in the environment, for the work place, for food and water supply, etc. Written by 40 internationally recognized experts, the 14(More)
A crucial step of the self-splicing reaction of group II intron ribozymes is the recognition of the 5' exon by the intron. This recognition is achieved by two regions in domain 1 of the intron, the exon-binding sites EBS1 and EBS2 forming base pairs with the intron-binding sites IBS1 and IBS2 located at the end of the 5' exon. The complementarity of the(More)
Mg(2+)-Responsive riboswitches represent a fascinating example of bifunctional RNAs that sense Mg(2+) ions with high selectivity and autonomously regulate the expression of Mg(2+)-transporter proteins. The mechanism of the mgtA riboswitch is scarcely understood, and a detailed structural analysis is called for to study how this RNA can selectively recognize(More)
Group II intron self-splicing is essential for the correct expression of organellar genes in plants, fungi, and yeast, as well as of bacterial genes. Self-excision of these autocatalytic introns from the primary RNA transcript is achieved in a two-step mechanism that is apparently analogous to that of the eukaryotic spliceosome. The 2'-OH of a conserved(More)
Folding of group II introns is characterized by a first slow compaction of domain 1 (D1) followed by the rapid docking of other domains to this scaffold. D1 compaction initiates in a small subregion encompassing the κ and ζ elements. These two tertiary elements are also the major interaction sites with domain 5 to form the catalytic core. Here, we provide(More)