Wieden-Kothe, Ute
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Browsing Wieden-Kothe, Ute by Author "Wieden, Hans-Joachim"
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- ItemAn arginine-aspartate network in the active site of bacterial TruB is critical for catalyzing pseudouridine formation(Oxford University Press, 2014) Friedt, Jenna; Leavens, Fern M. V.; Mercier, Evan; Wieden, Hans-Joachim; Wieden-Kothe, UtePseudouridine synthases introduce the most common RNA modification and likely use the same catalytic mechanism. Besides a catalytic aspartate residue, the contributions of other residues for catalysis of pseudouridine formation are poorly understood. Here, we have tested the role of a conserved basic residue in the active site for catalysis using the bacterial pseudouridine synthase TruB targeting U55 in tRNAs. Substitution of arginine 181 with lysine results in a 2500-fold reduction of TruB’s catalytic rate without affecting tRNA binding. Furthermore, we analyzed the function of a second-shell aspartate residue (D90) that is conserved in all TruB enzymes and interacts with C56 of tRNA. Site-directed mutagenesis, biochemical and kinetic studies reveal that this residue is not critical for substrate binding but influences catalysis significantly as replacement of D90 with glutamate or asparagine reduces the catalytic rate 30- and 50-fold, respectively. In agreement with molecular dynamics simulations of TruB wild type and TruB D90N, we propose an electrostatic network composed of the catalytic aspartate (D48), R181 and D90 that is important for catalysis by finetuning the D48-R181 interaction. Conserved, negatively charged residues similar to D90 are found in a number of pseudouridine synthases, suggesting that this might be a general mechanism.
- ItemContribution of two conserved histidines to the dual activity of archael RNA guide-dependent and -independent pseudouridine synthase Cbf5(Cold Spring Harbor Laboratory Press, 2015) Tillault, Anne-Sophie; Fourmann, Jean-Baptiste; Loegler, Christine; Wieden, Hans-Joachim; Wieden-Kothe, Ute; Charpentier, BrunoIn all organisms, several distinct stand-alone pseudouridine synthase (PUS) family enzymes are expressed to isomerizeuridine into pseudouridine (Ψ) by specific recognition of RNAs. In addition, Ψs are generated in Archaea and Eukaryotes by PUS enzymes which are organized as ribonucleoprotein particles (RNP)—the box H/ACA s/snoRNPs. For this modification system, a unique TruB-like catalytic PUS subunit is associated with various RNA guides which specifically target and secure substrate RNAs by base-pairing. The archaeal Cbf5 PUS displays the special feature of exhibiting both RNA guide-dependent and -independent activities. Structures of substrate-bound TruB and H/ACA sRNP revealed the importance of histidines in positioning the target uridine in the active site. To analyze the respective role of H60 and H77, we have generated variants carrying alanine substitutions at these positions. The impact of the mutations was analyzed for unguided modifications U55 in tRNA and U2603 in 23S rRNA, and for activity of the box H/ACA Pab91 sRNP enzyme. H77 (H43 in TruB), but not H60, appeared to be crucial for the RNA guide-independent activity. In contrast to earlier suggestions, H60 was found to be noncritical for the activity of the H/ACA sRNP, but contributes together with H77 to the full activity of H/ACA sRNPs. The data suggest that a similar catalytic process was conserved in the two divergent pseudouridylation systems.