Trans-Translation in Helicobacter pylori: Essentiality of Ribosome Rescue and Requirement of Protein Tagging for Stress Resistance and Competence

BACKGROUND: The ubiquitous bacterial trans-translation is one of the most studied quality control mechanisms. Trans-translation requires two specific factors, a small RNA SsrA (tmRNA) and a protein co-factor SmpB, to promote the release of ribosomes stalled on defective mRNAs and to add a specific tag sequence to aberrant polypeptides to direct them to degradation pathways. Helicobacter pylori is a pathogen persistently colonizing a hostile niche, the stomach of humans. PRINCIPAL FINDINGS: We investigated the role of trans-translation in this bacterium well fitted to resist stressful conditions and found that both smpB and ssrA were essential genes. Five mutant versions of ssrA were generated in H. pylori in order to investigate the function of trans-translation in this organism. Mutation of the resume codon that allows the switch of template of the ribosome required for its release was essential in vivo, however a mutant in which this codon was followed by stop codons interrupting the tag sequence was viable. Therefore one round of translation is sufficient to promote the rescue of stalled ribosomes. A mutant expressing a truncated SsrA tag was viable in H. pylori, but affected in competence and tolerance to both oxidative and antibiotic stresses. This demonstrates that control of protein degradation through trans-translation is by itself central in the management of stress conditions and of competence and supports a regulatory role of trans-translation-dependent protein tagging. In addition, the expression of smpB and ssrA was found to be induced upon acid exposure of H. pylori. CONCLUSIONS: We conclude to a central role of trans-translation in H. pylori both for ribosome rescue possibly due to more severe stalling and for protein degradation to recover from stress conditions frequently encountered in the gastric environment. Finally, the essential trans-translation machinery of H. pylori is an excellent specific target for the development of novel antibiotics

Strongly coupled binuclear uranium-oxo complexes from uranyl oxo rearrangement and reductive silylation

The most common motif in uranium chemistry is the d0f0 uranyl ion [UO2]21 in which the oxo groups are rigorously linear and inert. Alternative geometries, such as the cis-uranyl, have been identified theoretically and implicated in oxo-atom transfer reactions that are relevant to environmental speciation and nuclear waste remediation. Single electron reduction is now known to impart greater oxo-group reactivity, but with retention of the linear OUO motif, and reactions of the oxo groups to form new covalent bonds remain rare. Here, we describe the synthesis, structure, reactivity and magnetic properties of a binuclear uranium–oxo complex. Formed through a combination of reduction and oxo-silylation and migration from a trans to a cis position, the new butterfly-shaped Si–OUO2UO–Si molecule shows remarkably strong UV–UV coupling and chemical inertness, suggesting that this rearranged uranium oxo motif might exist for other actinide species in the environment, and have relevance to the aggregation of actinide oxide clusters.JRC.E.6-Actinides researc

A Meta-Analysis of Voice and Its Promotive and Prohibitive Forms: Identification of Key Associations, Distinctions, and Future Research Directions

This article reports meta-analyses intended to clarify and enhance our understanding of voice and its promotive and prohibitive forms. We find that undifferentiated constructive voice is associated with a wide range of antecedents that fit in Morrison's (2014) five categories: (a) dispositions, (b) job and organizational attitudes and perceptions, (c) emotions, beliefs, and schemas, (d) supervisor and leader behavior, and (e) contextual factors. However, relative weight analyses reveal a highly dominant variable within each category (personal initiative, felt responsibility, engagement, leader–member exchange, and positive workplace climate). We also find that undifferentiated constructive voice has a moderate zero-order association with job performance that is nonsignificant when task performance and organizational citizenship behavior are also considered. Finally, we explore how associations vary as a function of whether voice is promotive or prohibitive. First, there are significant differences in associations with over a third of the antecedents (core self-evaluations, felt responsibility, organizational commitment, detachment, psychological safety, ethical leadership, and leader openness). Second, although promotive voice has a positive association with job performance, the opposite is true for prohibitive voice. We conclude with suggestions to enhance our understanding of voice, especially with respect to efforts needed to clarify and distinguish promotive and prohibitive voice.This accepted article is published as Chamberlin, M., Newton, D. W., & LePine, J. A. (2017). A meta-analysis of voice and its promotive and prohibitive forms: Identification of key associations, distinctions, and future research directions. Personnel Psychology 70(1), 11-71. doi: 10.1111/peps.12185. Posted with permission