Knowledge-based design of reagentless fluorescent biosensors from a designed ankyrin repeat protein

Designed ankyrin repeat proteins (DARPins) can be selected from combinatorial libraries to bind any target antigen. They show high levels of recombinant expression, solubility and stability, and contain no cysteine residue. The possibility of obtaining, from any DARPin and at high yields, fluorescent conjugates which respond to the binding of the antigen by a variation of fluorescence, would have numerous applications in micro- and nano-analytical sciences. This possibility was explored with Off7, a DARPin directed against the maltose binding protein (MalE) from Escherichia coli, with known crystal structure of the complex. Eight residues of Off7, whose solvent accessible surface area varies on association with the antigen but which are not in direct contact with the antigen, were individually mutated into cysteine and then chemically coupled with a fluorophore. The conjugates were ranked according to their relative sensitivities. All of them showed an increase in their fluorescence intensity on antigen binding by >1.7-fold. The best conjugate retained the same affinity as the parental DARPin. Its signal increased linearly and specifically with the concentration of antigen, up to 15-fold in buffer and 3-fold in serum when fully saturated, the difference being mainly due to the absorption of light by serum. Its lower limit of detection was equal to 0.3 nM with a standard spectrofluorometer. Titrations with potassium iodide indicated that the fluorescence variation was due to a shielding of the fluorescent group from the solvent by the antigen. These results suggest rules for the design of reagentless fluorescent biosensors from any DARPi

Identités franciscaines à l’âge des Réformes, sous la direction de Frédéric Meyer et Ludovic Viallet

Vingt-quatre auteurs écrivant en cinq langues (majoritairement français, mais aussi italien, anglais, allemand et espagnol) dans une grande diver­sité d’approches, ont contribué à ce livre issu de deux colloques tenus à Clermont-Ferrand en 2003 et à Chambéry en 2004. Leurs communications ont été réparties en quatre ensembles. Il y a d’abord « La vie franciscaine en choix et en débats », couvrant les réformes internes aux branches de l’ordre des Mineurs, du xive au xviie siècle. La deuxième pa..

Grado Giovanni Merlo, Au nom de saint François. Histoire des Frères mineurs et du franciscanisme jusqu’au début du XVIe siècle, traduit de l’italien par Jacqueline Gréal, préface de Giovanni Miccoli

Paru en italien à Padoue en 2003, ce panorama de la « question franciscaine » au sens large du terme, conçu dans un esprit de synthèse, rendra de grands services. En six chapitres, G. G. Merlo retrace la naissance d’une fraternité autour de François d’Assise et sa transformation en un ordre de Frères mineurs ; son expansion géographique et sociale ; ses tensions internes entre la mort de François en 1226 et celle de Bonaventure en 1274 et les problèmes posés par la tentation joachimite ; la c..

Grado Giovanni Merlo, Au nom de saint François. Histoire des Frères mineurs et du franciscanisme jusqu’au début du XVIe siècle, traduit de l’italien par Jacqueline Gréal, préface de Giovanni Miccoli

Paru en italien à Padoue en 2003, ce panorama de la « question franciscaine » au sens large du terme, conçu dans un esprit de synthèse, rendra de grands services. En six chapitres, G. G. Merlo retrace la naissance d’une fraternité autour de François d’Assise et sa transformation en un ordre de Frères mineurs ; son expansion géographique et sociale ; ses tensions internes entre la mort de François en 1226 et celle de Bonaventure en 1274 et les problèmes posés par la tentation joachimite ; la c..

Enhanced In Vitro Refolding of Fibroblast Growth Factor 15 with the Assistance of SUMO Fusion Partner

Fibroblast growth factor 15 (Fgf15) is the mouse orthologue of human FGF19. Fgf15 is highly expressed in the ileum and functions as an endocrine signal to regulate liver function, including bile acid synthesis, hepatocyte proliferation and insulin sensitivity. In order to fully understand the function of Fgf15, methods are needed to produce pure Fgf15 protein in the prokaryotic system. However, when expressed in Escherichia coli (E. coli), the recombinant Fgf15 protein was insoluble and found only in inclusion bodies. In the current study, we report a method to produce recombinant Fgf15 protein in E. coli through the use of small ubiquitin-related modifier (SUMO) fusion tag. Even though the SUMO has been shown to strongly improve protein solubility and expression levels, our studies suggest that the SUMO does not improve Fgf15 protein solubility. Instead, proper refolding of Fgf15 protein was achieved when Fgf15 was expressed as a partner protein of the fusion tag SUMO, followed by in vitro dialysis refolding. After refolding, the N-terminal SUMO tag was cleaved from the recombinant Fgf15 fusion protein by ScUlp1 (Ubiquitin-Like Protein-Specific Protease 1 from S. cerevisiae). With or without the SUMO tag, the refolded Fgf15 protein was biologically active, as revealed by its ability to reduce hepatic Cyp7a1 mRNA levels in mice. In addition, recombinant Fgf15 protein suppressed Cyp7a1 mRNA levels in a dose-dependent manner. In summary, we have developed a successful method to express functional Fgf15 protein in prokaryotic cells

Pediatric Measles Vaccine Expressing a Dengue Antigen Induces Durable Serotype-specific Neutralizing Antibodies to Dengue Virus

Dengue disease is an increasing global health problem that threatens one-third of the world's population. Despite decades of efforts, no licensed vaccine against dengue is available. With the aim to develop an affordable vaccine that could be used in young populations living in tropical areas, we evaluated a new strategy based on the expression of a minimal dengue antigen by a vector derived from pediatric live-attenuated Schwarz measles vaccine (MV). As a proof-of-concept, we inserted into the MV vector a sequence encoding a minimal combined dengue antigen composed of the envelope domain III (EDIII) fused to the ectodomain of the membrane protein (ectoM) from DV serotype-1. Immunization of mice susceptible to MV resulted in a long-term production of DV1 serotype-specific neutralizing antibodies. The presence of ectoM was critical to the immunogenicity of inserted EDIII. The adjuvant capacity of ectoM correlated with its ability to promote the maturation of dendritic cells and the secretion of proinflammatory and antiviral cytokines and chemokines involved in adaptive immunity. The protective efficacy of this vaccine should be studied in non-human primates. A combined measles–dengue vaccine might provide a one-shot approach to immunize children against both diseases where they co-exist

Expression Screening of Fusion Partners from an E. coli Genome for Soluble Expression of Recombinant Proteins in a Cell-Free Protein Synthesis System

While access to soluble recombinant proteins is essential for a number of proteome studies, preparation of purified functional proteins is often limited by the protein solubility. In this study, potent solubility-enhancing fusion partners were screened from the repertoire of endogenous E. coli proteins. Based on the presumed correlation between the intracellular abundance and folding efficiency of proteins, PCR-amplified ORFs of a series of highly abundant E. coli proteins were fused with aggregation-prone heterologous proteins and then directly expressed for quantitative estimation of the expression efficiency of soluble translation products. Through two-step screening procedures involving the expression of 552 fusion constructs targeted against a series of cytokine proteins, we were able to discover a number of endogenous E. coli proteins that dramatically enhanced the soluble expression of the target proteins. This strategy of cell-free expression screening can be extended to quantitative, global analysis of genomic resources for various purposes.National Research Foundation of KoreaKorea (South). Ministry of Education, Science and Technology (MEST) (grant 2011K000841)Korea (South). Ministry of Education, Science and Technology (MEST) (grant 2011-0027901