Efficient Indifferentiable Hashing into Ordinary Elliptic Curves

We provide the first construction of a hash function into ordinary elliptic curves that is indifferentiable from a random oracle, based on Icart\u27s deterministic encoding from Crypto 2009. While almost as efficient as Icart\u27s encoding, this hash function can be plugged into any cryptosystem that requires hashing into elliptic curves, while not compromising proofs of security in the random oracle model. We also describe a more general (but less efficient) construction that works for a large class of encodings into elliptic curves, for example the Shallue-Woestijne-Ulas (SWU) algorithm. Finally we describe the first deterministic encoding algorithm into elliptic curves in characteristic 3

Etude des interactions entre la kinésine mitotique humaine Eg5 et ses inhibiteurs

The human mitotic kinesin HsEg5 plays an essential role in cell division. This protein is required for the separation of the duplicated centrosomes and the formation of the mitotic spindle. Failure of HsEg5 function blocks centrosome migration and causes cells to arrest midway through mitosis with a characteristic monoastral spindle consisting of a radial array of microtubules surrounded by a ring of chromosomes. This particular phenotype can lead to cell death by the apoptotic pathway. HsEg5 is thus considered as a very promising target for cancer chemotherapy. In this study, we investigate the binding regions of several inhibitors targeting the motor domain of HsEg5. These studies were carried out by using hydrogen/deuterium exchange – mass spectrometry and mutagenesis. Our experimental approach has been successfully applied to localize a “hot spot” binding region on the motor domain and to characterize the mechanism of HsEg5 inhibition by monastrol and S-trityl-l-cysteine.La kinésine mitotique humaine HsEg5 est essentielle à la division cellulaire. Ce moteur moléculaire permet la séparation des centrosomes et la mise en place du fuseau mitotique, structure nécessaire au partage équitable de l'information génétique. La suppression de la fonction d'HsEg5 bloque les cellules en pré-métaphase avec un fuseau mitotique monoastral caractéristique constitué des deux centrosomes non séparés entourés d'un anneau de chromosomes et de microtubules. Le maintien de ce phénotype peut conduire à la mort cellulaire programmée via l'activation du point de contrôle du fuseau mitotique (transition métaphase-anaphase). HsEg5 est ainsi considérée comme une cible anticancéreuse particulièrement intéressante. Au cours de ces travaux, nous nous sommes intéressés aux interactions entre le domaine moteur d'HsEg5 et plusieurs inhibiteurs. Les zones d'interaction et de modifications conformationnelles ont été étudiées par échanges hydrogène/deutérium–spectrométrie de masse et mutagenèse dirigée. Cette approche expérimentale nous a permis d'identifier un « point chaud » d'inhibition sur le domaine moteur et de caractériser les mécanismes de deux inhibiteurs : le monastrol et le S-trityl-l-cystéine

Cryptanalysis of RSA signatures with fixed-pattern padding

Keywords. RSA signatures, fixed-pattern padding, affine redundancy. 1 Introduction RSA was invented in 1977 by Rivest, Shamir and Adleman [8], and is now themost widely used public-key cryptosytem. RSA is commonly used for providing privacy and authenticity of digital data, and securing web traffic between serversand browsers. A very common practice for signing with RSA is to first hash the message,add some padding, and then raise the result to the power of the decryption exponent. This paradigm is the basis of numerous standards such as PKCS #1v2.0 [9]

Structure and allosteric inhibition of excitatory amino acid transporter 1

International audienceHuman members of the solute carrier 1 (SLC1) family of transporters take up excitatory neurotransmitters in the brain and amino acids in peripheral organs. Dysregulation of their functions is associated to neurodegenerative disorders and cancer. Here we present the first crystal structures of a thermostabilized human SLC1 transporter, the excitatory amino acid transporter 1 (EAAT1), with and without allosteric and competitive inhibitors bound. The structures show novel architectural features of the human transporters, including intra-and extracellular domains with potential roles in transport function, as well as regulation by lipids and post-translational modifications. The coordination of the inhibitor in the structures and the change in the transporter dynamics measured by hydrogen-deuterium exchange mass spectrometry, reveal an allosteric mechanism of inhibition, whereby the transporter is locked in the outward-facing states of the transport cycle. Our results provide unprecedented insights into the molecular mechanisms of function and pharmacology of human SLC1 transporters. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use

Prepore Stability Controls Productive Folding of the BAM-independent Multimeric Outer Membrane Secretin PulD

Members of a group of multimeric secretion pores that assemble independently of any known membrane-embedded insertase in Gram-negative bacteria fold into a prepore before membrane-insertion occurs. The mechanisms and the energetics that drive the folding of these proteins are poorly understood. Here, equilibrium unfolding and hydrogen/deuterium exchange monitored by mass spectrometry indicated that a loss of 4-5 kJ/mol/protomer in the N-3 domain that is peripheral to the membrane-spanning C domain in the dodecameric secretin PulD, the founding member of this class, prevents pore formation by destabilizing the prepore into a poorly structured dodecamer as visualized by electron microscopy. Formation of native PulD-multimers by mixing protomers that differ in N-3 domain stability, suggested that the N-3 domain forms a thermodynamic seal onto the prepore. This highlights the role of modest free energy changes in the folding of preintegration forms of a hyperstable outer membrane complex and reveals a key driving force for assembly independently of the beta-barrel assembly machinery

Post-translational acylation controls the folding and functions of the CyaA RTX toxin

International audienceThe adenylate cyclase (CyaA) toxin is a major virulence factor of Bordetella pertussis, the causative agent of whooping cough. CyaA is synthetized as a pro-toxin, pro-CyaA, and converted into its cytotoxic form upon acylation of two lysines. After secretion, CyaA invades eukaryotic cells and produces cAMP, leading to host defense subversion. To gain further insights into the effect of acylation, we compared the functional and structural properties of pro-CyaA and CyaA proteins. HDX-MS results show that the refolding process of both proteins upon progressive urea removal is initiated by calcium binding to the C-terminal RTX domain. We further identified a critical hydrophobic segment, distal from the acylation region, that folds at higher urea concentration in CyaA than in pro-CyaA. Once refolded into monomers, CyaA is more compact and stable than pro-CyaA, due to a complex set of interactions between domains. Our HDX-MS data provide direct evidence that the presence of acyl chains in CyaA induces a significant stabilization of the apolar segments of the hydrophobic domain and of most of the acylation region. We propose a refolding model dependent on calcium and driven by local and distal acylation-dependent interactions within CyaA. Therefore, CyaA acylation is not only critical for cell intoxication, but also for protein refolding into its active conformation. Our data shed light on the complex relationship between post-translational modifications, structural disorder and protein folding. Coupling calcium-binding and acylation-driven folding is likely pertinent for other repeat-in-toxin cytolysins produced by many Gram-negative bacterial pathogens.-O'Brien, D. P., Cannella, S. E., Voegele, A., Raoux-Barbot, D., Davi, M., Douché, T., Matondo, M., Brier, S., Ladant, D., Chenal, A. Post-translational acylation controls the folding and functions of the CyaA RTX toxin

Post-translational acylation controls the folding and functions of the CyaA RTX toxin

The adenylate cyclase (CyaA) toxin is a major virulence factor of Bordetella pertussis, the causative agent of whooping cough. CyaA is synthetized as a pro-toxin, pro-CyaA, and converted into its cytotoxic form upon acylation of two lysines. After secretion, CyaA invades eukaryotic cells and produces cAMP, leading to host defense subversion. To gain further insights into the effect of acylation, we compared the functional and structural properties of pro-CyaA and CyaA proteins. HDX-MS results show that the refolding process of both proteins upon progressive urea removal is initiated by calcium binding to the C-terminal RTX domain. We further identified a critical hydrophobic segment, distal from the acylation region, that folds at higher urea concentration in CyaA than in pro-CyaA. Once refolded into monomers, CyaA is more compact and stable than pro-CyaA, due to a complex set of interactions between domains. Our HDX-MS data provide direct evidence that the presence of acyl chains in CyaA induces a significant stabilization of the apolar segments of the hydrophobic domain and of most of the acylation region. We propose a refolding model dependent on calcium and driven by local and distal acylation-dependent interactions within CyaA. Therefore, CyaA acylation is not only critical for cell intoxication, but also for protein refolding into its active conformation. Our data shed light on the complex relationship between post-translational modifications, structural disorder and protein folding. Coupling calcium-binding and acylation-driven folding is likely pertinent for other repeat-in-toxin cytolysins produced by many Gram-negative bacterial pathogens.-O'Brien, D. P., Cannella, S. E., Voegele, A., Raoux-Barbot, D., Davi, M., Douché, T., Matondo, M., Brier, S., Ladant, D., Chenal, A. Post-translational acylation controls the folding and functions of the CyaA RTX toxin

The stress sigma factor of RNA polymerase RpoS/σ S is a solvent-exposed open molecule in solution

International audienceIn bacteria, one primary and multiple alternative sigma (σ) factors associate with the RNA polymerase core enzyme (E) to form holoenzymes (Eσ) with different promoter recognition specificities. The alternative σ factor RpoS/σ S is produced in stationary phase and under stress conditions and reprograms global gene expression to promote bacterial survival. To date, the three-dimensional structure of a full-length free σ factor remains elusive. The current model suggests that extensive interdomain contacts in a free σ factor result in a compact conformation that masks the DNA-binding determinants of σ, explaining why a free σ factor does not bind double-stranded promoter DNA efficiently. Here, we explored the solution conformation of σ S using amide hydrogen/deuterium exchange coupled with mass spectrometry, NMR, analytical ultracentrifugation and molecular dynamics. Our data strongly argue against a compact conformation of free σ S. Instead, we show that σ S adopts an open conformation in solution in which the folded σ 2 and σ 4 domains are interspersed by domains with a high degree of disorder. These findings suggest that E binding induces major changes in both the folding and domain arrangement of σ S and provide insights into the possible mechanisms of regulation of σ S activity by its chaperone Crl

Disorder-To-Order Transitions and Post-Translational Acylation Control the Folding and Activity of the Bordetella Pertussis CyaA Toxin

Place: Cambridge Publisher: Cell Press WOS:000513023201234Communication à la conférence : 64th Annual Meeting of the Biophysical-Society [San Diego, CA]Date: FEB 15-19, 2020International audienc

Structural Characterization of Whirlin Reveals an Unexpected and Dynamic Supramodule Conformation of Its PDZ Tandem

International audienceHearing relies on the transduction of sound-evoked vibrations into electric signals, occurring in the stereocilia bundle of hair cells. The bundle is organized in a staircase pattern formed by rows of packed stereocilia. This architecture is pivotal to transduction and involves a network of scaffolding proteins with hitherto uncharacterized features. Key interactions in this network are mediated by PDZ domains. Here, we describe the architecture of the first two PDZ domains of whirlin, a protein involved in these assemblies and associated with congenital deaf-blindness. C-terminal hairpin extensions of the PDZ domains mediate the transient supramodular assembly, which improves the binding capacity of the first domain. We determined a detailed structural model of the closed conformation of the PDZ tandem and characterized its equilibrium with an ensemble of open conformations. The structural and dynamic behavior of this PDZ tandem provides key insights into the regulatory mechanisms involved in the hearing machinery