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Rüdiger Welz

Publications and source records attributed to Rüdiger Welz.

4 recordsLinked to original sources
PubMed2006

Tandem riboswitch architectures exhibit complex gene control functions.

Riboswitches are structured RNAs typically located in the 5' untranslated regions of bacterial mRNAs that bind metabolites and control gene expression. Most riboswitches sense one metabolite and function as simple genetic switches. However, we found that the 5' region of the Bacillus clausii metE messenger RNA includes two riboswitches that respond to S-adenosylmethionine and coenzyme B12. This tandem arrangement yields a composite gene control system that functions as a two-input Boolean NOR logic gate. These findings and the discovery of additional tandem riboswitch architectures reveal how simple RNA elements can be assembled to make sophisticated genetic decisions without involving protein factors.

5' Untranslated Regions↗
PubMed2005

Evidence for a second class of S-adenosylmethionine riboswitches and other regulatory RNA motifs in alpha-proteobacteria.

BACKGROUND: Riboswitches are RNA elements in the 5' untranslated leaders of bacterial mRNAs that directly sense the levels of specific metabolites with a structurally conserved aptamer domain to regulate expression of downstream genes. Riboswitches are most common in the genomes of low GC Gram-positive bacteria (for example, Bacillus subtilis contains examples of all known riboswitches), and some riboswitch classes seem to be restricted to this group. RESULTS: We used comparative sequence analysis and structural probing to identify five RNA elements (serC, speF, suhB, ybhL, and metA) that reside in the intergenic regions of Agrobacterium tumefaciens and many other alpha-proteobacteria. One of these, the metA motif, is found upstream of methionine biosynthesis genes and binds S-adenosylmethionine (SAM). This natural aptamer most likely functions as a SAM riboswitch (SAM-II) with a consensus sequence and structure that is distinct from the class of SAM riboswitches (SAM-I) predominantly found in Gram-positive bacteria. The minimal functional SAM-II aptamer consists of fewer than 70 nucleotides, which form a single stem and a pseudoknot. Despite its simple architecture and lower affinity for SAM, the SAM-II aptamer strongly discriminates against related compounds. CONCLUSION: SAM-II is the only metabolite-binding riboswitch class identified so far that is not found in Gram-positive bacteria, and its existence demonstrates that biological systems can use multiple RNA structures to sense a single chemical compound. The two SAM riboswitches might be 'RNA World' relics that were selectively retained in certain bacterial lineages or new motifs that have emerged since the divergence of the major bacterial groups.

Alphaproteobacteria↗
PubMed2004

Stereoselective synthesis of trans-threo-trans-oligopyrrolidines: potential agents for RNA cleavage.

The 2,5-trans-substituted oligopyrrolidines constitute a promising class of novel RNA-binding agents as well as potential building blocks for artificial anion channels. A convergent synthesis of terpyrrolidine 1 and pyrrolidino-THF-pyrrolidine 2 is reported, relying upon convergent coupling of 2,5-trans-pyrrolidinecarboxaldehydes through bridging alkyne units under Felkin-Anh control and subsequent closure of the central ring. After complete deprotection, the free polyamine products were isolated in excellent yield and purity. Crystal structure analyses of a terpyrrolidine and a pyrrolidino-THF-pyrrolidine documented their helical privileged conformations. The compounds were then screened for RNA cleavage activity. Unlike the only weakly active simple polyamines, p-nitrosulfonamide 33 was found to induce cleavage at mM concentrations under physiologically relevant conditions.

Crystallization↗