Search

Viral pathogens are an ongoing threat to public health worldwide. Analysing their dependence on host biosynthetic pathways could lead to effective antiviral therapies.sup.1. Here we integrate proteomic analyses of polysomes with functional genomics and pharmacological interventions to define how enteroviruses and flaviviruses remodel host polysomes to synthesize viral proteins and disable host protein production. We find that infection with polio, dengue or Zika virus markedly modifies polysome composition, without major changes to core ribosome stoichiometry. These viruses use different strategies to evict a common set of translation initiation and RNA surveillance factors from polysomes while recruiting host machineries that are specifically required for viral biogenesis. Targeting these specialized viral polysomes could provide a new approach for antiviral interventions. For example, we find that both Zika and dengue use the collagen proline hydroxylation machinery to mediate cotranslational modification of conserved proline residues in the viral polyprotein. Genetic or pharmacological inhibition of proline hydroxylation impairs nascent viral polyprotein folding and induces its aggregation and degradation. Notably, such interventions prevent viral polysome remodelling and lower virus production. Our findings delineate the modular nature of polysome specialization at the virus-host interface and establish a powerful strategy to identify targets for selective antiviral interventions. A proteomics-based strategy is used to examine how three different RNA viruses (polio, Zika and dengue) remodel translation in the host to recruit host machineries necessary for the production of viral proteins., Author(s): Ranen Aviner [sup.1] [sup.2] , Kathy H. Li [sup.3] , Judith Frydman [sup.2] , Raul Andino [sup.1] Author Affiliations: (1) Department of Microbiology and Immunology, University of California, San [...]

Ethylbenzene dehydrogenase (EbDH; enzyme commission (EC) number: 1.17.99.2) is a unique biocatalyst that hydroxylates alkylaromatic and alkylheterocyclic compounds to (S)-secondary alcohols under anaerobic conditions. The enzyme exhibits a high promiscuity catalyzing oxidation of over 30 substrates, inter alia, para-substituted alkylphenols and alkylanilines. Secondary alcohols with OH and N[H.sub.2] substituents in the aromatic ring are highly valuable synthons for many biologically active compounds in the fine chemical industry. EbDH hydroxylates most of the studied compounds highly enantioselectively, except for five substrates that harbour OH and N[H.sub.2] groups in the para position, which exhibit a significant decrease in the percent enantiomeric excess (% ee). This phenomenon is inconsistent with the previously suggested enzyme mechanism, but it may be linked to a stabilization of the carbocation intermediate by deprotonation of the OH or N[H.sub.2] substituent in the active site that yields a transient quinone (imine) ethide species. This would initiate an alternative reaction pathway involving the addition of a water molecule to a C=C double bond. This hypothesis was cross-validated by density functional theory (DFT) cluster modelling of the alternative reaction pathway with 4-ethylphenol, as well as by experimental assessment of the pH dependency of enantiomeric excesses. The results reported herein suggest that the alternative reaction pathway may significantly contribute to the overall reaction if the carbocation intermediates are stabilized by deprotonation. Key words: ethylbenzene dehydrogenase, molybdenum enzyme, chiral alcohols, DFT. L'ethylbenzene dehydrogenase (EC 1.17.99.2) est unbiocatalyseur unique qui hydroxyle les composes alkylaromatiques et alkyl heterocycliques pour donner des enantiomeres S d'alcools secondaires dans des conditions anaerobies. L'enzyme manifeste une importante promiscuite, catalysant l'oxydation de plus de 30 substrats, entre autres des alkylphenols et des alkylanilines substitues en para. Les alcools secondaires possedant des substituants OH et N[H.sub.2] sur le noyau aromatique sont des synthons tres utiles pour de nombreux composes biologiquement actifs dans l'industrie des produits de chimie fine. L'ethylbenzene hydroxylase hydroxyle de maniere tres enantioselective la plupart des composes etudies, excepte cinq substrats porteurs de groupements OH et N[H.sub.2] en position para, pour lesquels on observe une diminution significative de l'exces enantiomerique (ee %). Ce phenomene ne concorde pas avec le mecanisme enzymatique propose anterieurement, mais il pourrait etre lie a une stabilisation des carbocations intermediaires par deprotonation du substituant OH ou N[H.sub.2] au site actif donnant une espece ethide de quinone (imine) transitoire. Cela ouvrirait un autre chemin de reaction comprenant l'ajout d'une molecule d'eau sur une double liaison C=C. On a procede a une validation croisee de cette hypothese par modelisation, fondee sur la theorie de la fonctionnelle de la densite (DFT) et un modele d'agregat, du chemin de reaction de rechange avec le 4-ethylphenol, ainsi que par evaluation experimentale de la dependance des exces enantiometriques au pH. Les resultats presentes donnent a penser que le chemin de reaction de rechange pourrait contribuer considerablement a la reaction globale si les carbocations intermediaries sont stabilises par deprotonation. [Traduit par la Redaction] Mots-cles: ethylbenzene hydrolase, enzyme a molybdene, alcools chiraux, DFT., Introduction Ethylbenzene dehydrogenase (EbDH) is a molybdoenzyme belonging to the dimethyl sulfoxide (DMSO) reductase family, (1,2) and catalyzes the oxygen-independent, stereoselective hydroxylation of ethylbenzene to (S)-1-phenylethanol. It is the first [...]