Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
January 30, 2014
Very Important Papers:
Active Efflux Influences the Potency of Quorum-Sensing Inhibitors in Pseudomonas aeruginosa
Joseph D. Moore, Joseph P. Gerdt, Nora R. Eibergen, and Helen E. Blackwell*
Small molecules capable of inhibiting bacterial cell--cell signaling, or quorum sensing (QS), are of significant interest as new chemical tools and potential anti-infective agents. Gram-negative bacteria predominately use N-acyl L-homoserine lactone (AHL) signals for QS. Now, Helen E. Blackwell (University of Wisconsin) and co-workers have shown that a variety of AHL-derived QS inhibitors in the pathogen Pseudomonas aeruginosa are substrates of its MexAB-OprM drug-efflux pump. In contrast, an aminobenzimidazole-type QS inhibitor does not display this efflux-induced reduction in potency. These results suggest that active efflux will need to be considered in the design of new QS modulators in P. aeruginosa and other bacteria.
Catalytic Scope of the Thiamine-Dependent Multifunctional Enzyme Cyclohexane-1,2-dione Hydrolase
Sabrina Loschonsky, Simon Waltzer, Sonja Fraas, Tobias Wacker, Susana L. A. Andrade, Peter M. H. Kroneck, and Michael Müller*
Cyclohexane-1,2-dione hydrolase (CDH) is a thiamine diphosphate-dependent enzyme that can accept a number of aromatic aldehydes that were previously hard to convert. Now, Michael Müller (Universität Freiburg) and co-workers have expressed CDH in E. coli and the recombinant CDH showed the same C–C bond-cleavage and C–C bond-formation activities as the wild-type enzyme. Furthermore, CDH catalyzes the asymmetric cross-benzoin reaction of aromatic aldehydes and pyruvate, up to quantitative conversion and 92–99% ee. On a semipreparative scale, the sterically demanding substrates 4-(tert-butyl)benzaldehyde and 2-naphthaldehyde, respectively, were transformed into the corresponding 2-hydroxyketone products in high yields. Additionally, certain benzaldehydes with electron-withdrawing substituents were identified as potential inhibitors of the C–C bond-formation activity of CDH. In a related paper, published simultaneously in ChemCatChem, M. Müller and co-workers also characterized the ability of CDH to catalyze the enantio-selective formation of (S)-acetoin by homocoupling of pyruvate, homocoupling of acetaldehyde, and cross-coupling of pyruvate and acetaldehyde.
Recently Published Articles
- 8-Cyclopropyl-2′-Deoxyguanosine: A Hole Trap for DNA-Mediated Charge Transport
Jiun Ru Wong and Dr. Fangwei Shao
Article first published online: 24 APR 2014 | DOI: 10.1002/cbic.201402018
Moving holes along DNA: Stable DNA duplexes containing 8-cyclopropyl-2′-deoxyguanosine (8CPG) were synthesized to investigate C8-modified deoxyguanosine as a kinetic trap for transient hole occupancy on guanines during DNA-mediated hole transport (HT). Photoirradiation of anthraquinone covalently tethered to the duplex induced oxidative decomposition of 8CPG through DNA HT along adenine tracts.
- An Expanded Set of Fluorogenic Sulfatase Activity Probes
Elizabeth L. Smith, Prof. Carolyn R. Bertozzi and Prof. Kimberly E. Beatty
Article first published online: 24 APR 2014 | DOI: 10.1002/cbic.201400032
Revealing sulfatases: Two new fluorogenic enzyme probes, 3-O-methylfluorescein sulfate and resorufin-sulfate, display a large increase in quantum yield upon hydrolysis by sulfatases. Both probes enable rapid, sensitive detection of sulfatase activity in a protein gel assay format, which allows the examination of sulfatases from a variety of mycobacterial pathogens.
- Modulating the pKa of a Tyrosine in KlenTaq DNA Polymerase that Is Crucial for Abasic Site Bypass by in Vivo Incorporation of a Non-canonical Amino Acid
Nina Blatter, Alexander Prokup, Prof. Dr. Alexander Deiters and Prof. Dr. Andreas Marx
Article first published online: 24 APR 2014 | DOI: 10.1002/cbic.201400051
Artificial bypass surgery: The non-canonical amino acid 2,3,5-fluorotyrosine was successfully incorporated into KlenTaq DNA polymerase at position 671. The fluorinated analogue modulated the pKa of the Y671 hydroxy group. Thus, the importance of hydrogen bonding in the bypass of an abasic site has been shown, specifically, the impact of the hydrogen bond between N3 of the incoming dATP and the hydroxy group of Y671.
- Selective DNA-Binding by Designed Bisbenzamidine-Homeodomain Chimeras
Jesús Mosquera, Jéssica Rodríguez, Prof. M. Eugenio Vázquez and Prof. José L. Mascareñas
Article first published online: 24 APR 2014 | DOI: 10.1002/cbic.201400079
Groovy attraction: Conjugates of the helix 3 region of a Q50K engrailed homeodomain with bisbenzamidine minor-groove DNA binders failed to bind DNA. However, modifications that increase the α-helical folding propensity of the peptide allowed specific DNA binding by a bipartite (major/minor groove) interaction.
- RNA Aminoacylation Mediated by Sequential Action of Two Ribozymes and a Nonactivated Amino Acid
Dr. Jiacui Xu, Dr. Bettina Appel, Darko Balke, Claudia Wichert and Prof. Dr. Sabine Müller
Article first published online: 24 APR 2014 | DOI: 10.1002/cbic.201300741
Aminoacylation in the RNA world: RNA aminoacylation has been achieved by sequential action of two ribozymes and nonactivated phenylalanine. RNA 1 loads “naked” phenylalanine onto its phosphorylated 5′ terminus, thereby forming a high-energy mixed anhydride. Upon complex formation with RNA 2, phenylalanine is transferred from the 5′ terminus of RNA 1 to the 3′ terminus of RNA 2.