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Immunoglobulin E and its interactions with receptors FcϵRI and CD23 play a central role in allergic disease. Omalizumab, a clinically approved therapeutic antibody, inhibits the interaction between IgE and FcϵRI, preventing mast cell and basophil activation, and blocks IgE binding to CD23 on B cells and antigen-presenting cells. We solved the crystal structure of the complex between an omalizumab-derived Fab and IgE-Fc, with one Fab bound to each Cϵ3 domain. Free IgE-Fc adopts an acutely bent structure, but in the complex it is only partially bent, with large-scale conformational changes in the Cϵ3 domains that inhibit the interaction with FcϵRI. CD23 binding is inhibited sterically due to overlapping binding sites on each Cϵ3 domain. Studies of omalizumab Fab binding in solution demonstrate the allosteric basis for FcϵRI inhibition and, together with the structure, reveal how omalizumab may accelerate dissociation of receptor-bound IgE from FcϵRI, exploiting the intrinsic flexibility and allosteric potential of IgE.

Botulinum neurotoxin A (BoNT/A) belongs to the most dangerous class of bioweapons. Despite this, BoNT/A is used to treat a wide range of common medical conditions such as migraines and a variety of ocular motility and movement disorders. BoNT/A is probably best known for its use as an antiwrinkle agent in cosmetic applications (including Botox and Dysport). BoNT/A application causes long-lasting flaccid paralysis of muscles through inhibiting the release of the neurotransmitter acetylcholine by cleaving synaptosomal-associated protein 25 (SNAP-25) within presynaptic nerve terminals. Two types of BoNT/A receptor have been identified, both of which are required for BoNT/A toxicity and are therefore likely to cooperate with each other: gangliosides and members of the synaptic vesicle glycoprotein 2 (SV2) family, which are putative transporter proteins that are predicted to have 12 transmembrane domains, associate with the receptor-binding domain of the toxin. Recently, fibroblast growth factor receptor 3 (FGFR3) has also been reported to be a potential BoNT/A receptor. In SV2 proteins, the BoNT/A-binding site has been mapped to the luminal domain, but the molecular details of the interaction between BoNT/A and SV2 are unknown. Here we determined the high-resolution crystal structure of the BoNT/A receptor-binding domain (BoNT/A-RBD) in complex with the SV2C luminal domain (SV2C-LD). SV2C-LD consists of a right-handed, quadrilateral β-helix that associates with BoNT/A-RBD mainly through backbone-to-backbone interactions at open β-strand edges, in a manner that resembles the inter-strand interactions in amyloid structures. Competition experiments identified a peptide that inhibits the formation of the complex. Our findings provide a strong platform for the development of novel antitoxin agents and for the rational design of BoNT/A variants with improved therapeutic properties.

G-protein coupled receptors (GPCRs) are the targets of over half of all prescribed drugs today. The UniProt database has records for about 800 proteins classified as GPCRs, but drugs have only been developed against 50 of these. Thus, there is huge potential in terms of the number of targets for new therapies to be designed. Several breakthroughs in GPCRs biased pharmacology, structural biology, modelling and scoring have resulted in a resurgence of interest in GPCRs as drug targets. Therefore, an international conference, sponsored by the Royal Society, with world-renowned researchers from industry and academia was recently held to discuss recent progress and highlight key areas of future research needed to accelerate GPCR drug discovery. Several key points emerged. Firstly, structures for all three major classes of GPCRs have now been solved and there is increasing coverage across the GPCR phylogenetic tree. This is likely to be substantially enhanced with data from x-ray free electron sources as they move beyond proof of concept. Secondly, the concept of biased signalling or functional selectivity is likely to be prevalent in many GPCRs, and this presents exciting new opportunities for selectivity and the control of side effects, especially when combined with increasing data regarding allosteric modulation. Thirdly, there will almost certainly be some GPCRs that will remain difficult targets because they exhibit complex ligand dependencies and have many metastable states rendering them difficult to resolve by crystallographic methods. Subtle effects within the packing of the transmembrane helices are likely to mask and contribute to this aspect, which may play a role in species dependent behaviour. This is particularly important because it has ramifications for how we interpret pre-clinical data. In summary, collaborative efforts between industry and academia have delivered significant progress in terms of structure and understanding of GPCRs and will be essential for resolving problems associated with the more difficult targets in the future., Naunyn-Schmiedeberg's archives of pharmacology, 388 (8), ISSN:0028-1298, ISSN:1432-1912

Protein-protein interactions are a central issue in biological processes and represent relevant therapeutic targets for the treatment of diseases. The design of antagonistic molecules directed towards the disruption of these interactions requires the specific recognition of protein surfaces. Quinoline oligoamide foldamers present all the properties to reach that point. They are easily synthesized and fold into helices (similar to α helices) which can be decorated. Thanks to biophysical studies (CD, SPR, RX diffraction), we demonstrate that these molecules are able to recognize protein surfaces. Two proteins have been studied: the human interleukin 4 and the human carbonic anhydrase II.The applied strategy (keeping the foldamer close to the protein surface via a linker) allowed us to gather structural information about foldamer protein interactions before any strong binding is established. The first crystal structure between a protein and an aromatic amide foldamer is reported., Les interactions protéine - protéine sont au centre de nombreux processus biologiques, et représentent des cibles thérapeutiques pertinentes pour le traitement de certaines maladies. La conception de molécules antagonistes visant à inhiber ces interactions requiert la reconnaissance spécifique d’une des surfaces protéiques impliquées. Les foldamères de type oligoamides de quinoline constituent de bons candidats. Leur production et leur fonctionnalisation sont relativement aisées. Ils adoptent des structures hélicoïdales semblables à celles rencontrées dans les protéines. Grâce à différentes techniques biophysiques (CD, SPR, diffraction des rayons X), nous montrons que ces molécules sont aptes à reconnaître une surface protéique. Deux protéines cibles ont été choisies : l’interleukine 4 et l’anhydrase carbonique humaine II.La stratégie retenue dans ce travail (ancrage du foldamère à la protéine via un bras espaceur) nous a permis d’obtenir des informations structurales sur les interactions foldamère – protéine avant toute optimisation de ces interactions. La première structure 3D d’un complexe foldamère de quinoline complexée à une protéine est décrite.