Aspergillus niger Protein EstA Defines a New Class of Fungal Esterases within the α/β Hydrolase Fold Superfamily of Proteins

AbstractFrom the fungus Aspergillus niger, we identified a new gene encoding protein EstA, a member of the α/β-hydrolase fold superfamily but of unknown substrate specificity. EstA was overexpressed and its crystal structure was solved by molecular replacement using a lipase-acetylcholinesterase chimera template. The 2.1 Å resolution structure of EstA reveals a canonical Ser/Glu/His catalytic triad located in a small pocket at the bottom of a large solvent-accessible, bowl-shaped cavity. Potential substrates selected by manual docking procedures were assayed for EstA activity. Consistent with the pocket geometry, preference for hydrolysis of short acyl/propyl chain substrates was found. Identification of close homologs from the genome of other fungi, of which some are broad host-range pathogens, defines EstA as the first member of a novel class of fungal esterases within the superfamily. Hence the structure of EstA constitutes a lead template in the design of new antifungal agents directed toward its pathogenic homologs

L’interaction fasciculine-acétylcholinestérase

L’acétylcholinestérase (AChE) est une enzyme-clé du mécanisme de transmission cholinergique. Les fas- ciculines, petites protéines « à trois doigts » isolées des venins de serpent mamba, sont des inhibiteurs puissants et sélectifs des AChEs de mammifères et poissons électriques. L’interaction fasciculine-AChE constitue un exemple parfait d’interaction entre une toxine animale et son récepteur macromoléculaire. En effet, par leur sélectivité, leur remarquable affinité, leur caractère d’inhibiteur allostérique, et leur nature protéique (donc accessible à la chimie des protéines et la biologie moléculaire), les fasciculines constituent des outils de choix, « scalpels moléculaires » pour l’étude de l’AChE. Les travaux présentés dans ce chapitre ont été menés selon une approche multidisciplinaire faisant intervenir des techniques distinctes, mais complémentaires, ainsi que de nombreuses collaborations. Les résultats obtenus contribuent à la définition des bases structurales et dynamiques non seulement des mécanismes d'inhibition de l’AChE par les fasciculines, mais également de la fonctionnalité du site périphérique de l’AChE, site distinct du site catalytique et doué de propriétés régulatrices

Contribution a l'etude de la purification et du mode d'action des toxines de venins de serpents Elapidae

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

A Triad of Crystals Sheds Light on MDGA Interference with Neuroligation

International audienceNeurexins and neuroligins form trans-synaptic complexes that promote synapse development. In this issue of Neuron, Aricescu and colleagues (Elegheert et al., 2017) complement and strengthen two recent reports by the Kim and Rudenko teams (Kim et al., 2017; Gangwar et al., 2017) to dissect the molecular determinants by which MDGAs challenge the neurexin-neuroligin partnership

Acetylcholinesterase Inhibition by Fasciculin: Crystal Structure of the Complex

International audienceThe crystal structure of the snake toxin fasciculin, bound to mouse acetylcholinesterase (mAChE), at 3.2 A resolution reveals a synergistic three-point anchorage consistent with the picomolar dissociation constant of the complex. Loop II of fasciculin contains a cluster of hydrophobic residues that interact with the peripheral anionic site of the enzyme and sterically occlude substrate access to the catalytic site. Loop I fits in a crevice near the lip of the gorge to maximize the surface area of contact of loop II at the gorge entry. The fasciculin core surrounds a protruding loop on the enzyme surface and stabilizes the whole assembly. Upon binding of fasciculin, subtle structural rearrangements of AChE occur that could explain the observed residual catalytic activity of the fasciculin-enzyme complex

Crystal Structure of Snake Venom Acetylcholinesterase in Complex with Inhibitory Antibody Fragment Fab410 Bound at the Peripheral Site EVIDENCE FOR OPEN AND CLOSED STATES OF A BACK DOOR CHANNEL

International audienceno abstrac

Structural insights into ligand interactions at the acetylcholinesterase peripheral anionic site

The peripheral anionic site on acetylcholinesterase (AChE), located at the active center gorge entry, encompasses overlapping binding sites for allosteric activators and inhibitors; yet, the molecular mechanisms coupling this site to the active center at the gorge base to modulate catalysis remain unclear. The peripheral site has also been proposed to be involved in heterologous protein associations occurring during synaptogenesis or upon neurodegeneration. A novel crystal form of mouse AChE, combined with spectrophotometric analyses of the crystals, enabled us to solve unique structures of AChE with a free peripheral site, and as three complexes with peripheral site inhibitors: the phenylphenanthridinium ligands, decidium and propidium, and the pyrogallol ligand, gallamine, at 2.20–2.35 Å resolution. Comparison with structures of AChE complexes with the peptide fasciculin or with organic bifunctional inhibitors unveils new structural determinants contributing to ligand interactions at the peripheral site, and permits a detailed topographic delineation of this site. Hence, these structures provide templates for designing compounds directed to the enzyme surface that modulate specific surface interactions controlling catalytic activity and non-catalytic heterologous protein associations

Report from the 28th Meeting on Toxinology, “Toxins: What’s up, Doc?”, Organized by the French Society of Toxinology on 28–29 November 2022

The French Society of Toxinology (SFET) organized its 28th annual meeting on 28–29 November 2022 (RT28). The central theme of this meeting was “Toxins: What’s up, Doc?”, emphasizing the latest findings on animal, bacterial, algal, plant and fungal toxins through sessions dedicated to deep learning, toxin tracking and toxinomic advances, shared by ca. 80 participants. The abstracts of the 10 invited and 11 selected lectures and 15 posters, along with the names of the Best Oral Communication and Best Poster awardees, are presented in this report

The ESTHER database on alpha/beta hydrolase fold proteins - An overview of recent developments

International audienceThe ESTHER database, dedicated to ESTerases and alpha/beta-Hydrolase Enzymes and Relatives (https://bioweb.supagro.inra.fr/ESTHER/general?what=index), offers online access to a continuously updated, sequence-based classification of proteins harboring the alpha/beta hydrolase fold into families and subfamilies. In particular, the database proposes links to the sequences, structures, ligands and huge diversity of functions of these proteins, and to the related literature and other databases. Taking advantage of the promiscuity of enzymatic function, many engineered esterases, lipases, epoxide-hydrolases, haloalkane dehalogenases are used for biotechnological applications. Finding means for detoxifying those protein members that are targeted by insecticides, herbicides, antibiotics, or for reactivating human cholinesterases when inhibited by nerve gas, are still active areas of research. Using or improving the capacity of some enzymes to breakdown plastics with the aim to recycle valuable material and reduce waste is an emerging challenge. Most hydrolases in the superfamily are water-soluble and act on or are inhibited by small organic compounds, yet in a few subfamilies some members interact with other, unrelated proteins to modulate activity or trigger functional partnerships. Recent development in 3D structure prediction brought by AI-based programs now permits analysis of enzymatic mechanisms for a variety of hydrolases with no experimental 3D structure available. Finally, mutations in as many as 34 of the 120 human genes compiled in the database are now linked to genetic diseases, a feature fueling research on early detection, metabolic pathways, pharmacological treatment or enzyme replacement therapy. Here we review those developments in the database that took place over the latest decade and discuss potential new applications and recent and future expected research in the field