Unraveling the Mechanism of a LOV Domain Optogenetic Sensor:A Glutamine Lever Induces Unfolding of the Jα Helix

Light-activated protein domains provide a convenient, modular, and genetically encodable sensor for optogenetics and optobiology. Although these domains have now been deployed in numerous systems, the precise mechanism of photoactivation and the accompanying structural dynamics that modulate output domain activity remain to be fully elucidated. In the C-terminal light-oxygen-voltage (LOV) domain of plant phototropins (LOV2), blue light activation leads to formation of an adduct between a conserved Cys residue and the embedded FMN chromophore, rotation of a conserved Gln (Q513), and unfolding of a helix (Jα-helix) which is coupled to the output domain. In the present work, we focus on the allosteric pathways leading to Jα helix unfolding in Avena sativa LOV2 (AsLOV2) using an interdisciplinary approach involving molecular dynamics simulations extending to 7 μs, time-resolved infrared spectroscopy, solution NMR spectroscopy, and in-cell optogenetic experiments. In the dark state, the side chain of N414 is hydrogen bonded to the backbone N-H of Q513. The simulations predict a lever-like motion of Q513 after Cys adduct formation resulting in a loss of the interaction between the side chain of N414 and the backbone C═O of Q513, and formation of a transient hydrogen bond between the Q513 and N414 side chains. The central role of N414 in signal transduction was evaluated by site-directed mutagenesis supporting a direct link between Jα helix unfolding dynamics and the cellular function of the Zdk2-AsLOV2 optogenetic construct. Through this multifaceted approach, we show that Q513 and N414 are critical mediators of protein structural dynamics, linking the ultrafast (sub-ps) excitation of the FMN chromophore to the microsecond conformational changes that result in photoreceptor activation and biological function

Heterobivalent Inhibitors of Acetyl-CoA Carboxylase: Drug Target Residence Time and Time-Dependent Antibacterial Activity

The relationship between drug–target residence time and the post-antibiotic effect (PAE) provides insights into target vulnerability. To probe the vulnerability of bacterial acetyl-CoA carboxylase (ACC), a series of heterobivalent inhibitors were synthesized based on pyridopyrimidine 1 and moiramide B (3) which bind to the biotin carboxylase and carboxyltransferase ACC active sites, respectively. The heterobivalent compound 17, which has a linker of 50 Å, was a tight binding inhibitor of Escherichia coli ACC (Kiapp 0.2 nM) and could be displaced from ACC by a combination of both 1 and 3 but not just by 1. In agreement with the prolonged occupancy of ACC resulting from forced proximity binding, the heterobivalent inhibitors produced a PAE in E. coli of 1–4 h in contrast to 1 and 3 in combination or alone, indicating that ACC is a vulnerable target and highlighting the utility of kinetic, time-dependent effects in the drug mechanism of action

Heterobivalent Inhibitors of Acetyl-CoA Carboxylase: Drug Target Residence Time and Time-Dependent Antibacterial Activity

The relationship between drug–target residence time and the post-antibiotic effect (PAE) provides insights into target vulnerability. To probe the vulnerability of bacterial acetyl-CoA carboxylase (ACC), a series of heterobivalent inhibitors were synthesized based on pyridopyrimidine 1 and moiramide B (3) which bind to the biotin carboxylase and carboxyltransferase ACC active sites, respectively. The heterobivalent compound 17, which has a linker of 50 Å, was a tight binding inhibitor of Escherichia coli ACC (Kiapp 0.2 nM) and could be displaced from ACC by a combination of both 1 and 3 but not just by 1. In agreement with the prolonged occupancy of ACC resulting from forced proximity binding, the heterobivalent inhibitors produced a PAE in E. coli of 1–4 h in contrast to 1 and 3 in combination or alone, indicating that ACC is a vulnerable target and highlighting the utility of kinetic, time-dependent effects in the drug mechanism of action

Bologna - Cinquant'anni di libri per ragazzi da tutto il mondo

Gli sviluppi della letteratura per l'infanzia in tutte le aree geografico-culturali del mondo nel periodo che va dal 1964, anno in cui si tenne la prima Fiera Internazionale del libro per Ragazzi di Bologna, al 2013, anno di celebrazione del suo cinquantenario e il ruolo giocato dalla Fiera (favorendo contatti e scambi culturali, promuovendo e premiando prodotti di qualit\ue0, dando visibilit\ue0 a culture marginali), in questa specifica storia della letteratura a livello planetario

Bologna - Fifty Years of Children's Books from Around the World

To mark the occasion of Bologna Children's Book Fair's Fiftieth Anniversary, a look back over its history, but, more generally, a look at how children's books have developed over the last fifty years since the beginning of the Fair. Children's literature scholars from all parts of the world stepped out enthusiastically to outline the history and state-of-the-art of books for children in their part of the world. The result is a fascinating overview showing interesting differences due to political social, and cultural features in the way children's books have taken hold, sometimes slowly, sometimes explosively. The essays provide stimulating insights into how children's books are themselves a child of their times, impacted by ideology, the dominant culture or countercultures of their day