Linker-extended native cyanovirin-N facilitates PEGylation and potently inhibits HIV-1 by targeting the glycan ligand

Cyanovirin-N (CVN) potently inhibits human immunodeficiency virus type 1 (HIV-1) infection, but both cytotoxicity and immunogenicity have hindered the translation of this protein into a viable therapeutic. A molecular docking analysis suggested that up to 12 residues were involved in the interaction of the reverse parallel CVN dimer with the oligosaccharide targets, among which Leu-1 was the most prominent hot spot residue. This finding provided a possible explanation for the lack of anti-HIV-1 activity observed with N-terminal PEGylated CVN. Therefore, linker-CVN (LCVN) was designed as a CVN derivative with a flexible and hydrophilic linker (Gly4Ser)3 at the N-terminus. The N-terminal α-amine of LCVN was PEGylated to create 10 K PEG-aldehyde (ALD)-LCVN. LCVN and 10 K PEG-ALD-LCVN retained the specificity and affinity of CVN for high mannose N-glycans. Moreover, LCVN exhibited significant anti-HIV-1 activity with attenuated cytotoxicity in the HaCaT keratinocyte cell line and MT-4 T lymphocyte cell lines. 10 K PEG-ALD-LCVN also efficiently inactivated HIV-1 with remarkably decreased cytotoxicity and pronounced cell-to-cell fusion inhibitory activity in vitro. The linker-extended CVN and the mono-PEGylated derivative were determined to be promising candidates for the development of an anti-HIV-1 agent. This derivatization approach provided a model for the PEGylation of biologic candidates without introducing point mutations. © 2014 Chen et al

Mechanistic Investigations of Anaerobic Sulfatase-Maturating Enzyme: Direct C β H-Atom Abstraction Catalyzed by a Radical AdoMet Enzyme

International audienceSulfatases are unique in requiring an essential post-translational modification of a critical active-site cysteinyl or seryl residue to 3-oxoalanine usually called C alpha-formylglycine (FGly). This post-translational modification is catalyzed anaerobically by anaerobic Sulfatase Maturating Enzyme (anSME), a member of the radical AdoMet superfamily. Using a new labeled substrate, we demonstrate that anSME uses a 5'-deoxyadenosyl radical to catalyze direct H-atom abstraction from the substrate. We thus established that anSMEs are the first radical AdoMet enzymes catalyzing a post-translational modification involving C(beta) H-atom abstraction from an active site cysteinyl or seryl residue. This mechanistic study allowed us to decipher the first steps of the mechanism of this new radical AdoMet enzyme family

Comparative NMR analysis of cellooligosaccharide hydrolysis by GH9 bacterial and plant endo-1,4-ss-glucanases

H-1 NMR spectroscopy has been used to analyze the product profiles arising from the hydrolysis of cellooligosaccharides by family GH9 cellulases. The product profiles obtained with the wild type and several active site mutants of a bacterial processive endoglucanase, Tf Cel9A, were compared with those obtained by a randomly acting plant endoglucanase, PttCe19A. PttCe19A is an orthologue of the Arabidopsis endocellulase, Korrigan, which is required for efficient cellulose biosynthesis. As expected, poplar PttCe19A was shown to catalyze the degradation of cellooligosaccharides by inversion of the configuration of the anomeric carbon. The product analyses showed that the number of interactions between the glucose units of the substrate and the aromatic residues in the enzyme active sites determines the point of cleavage in both enzymes

Soft Matter

Protein-ligand interactions on liquid-solid interfaces governed the design of functional biomaterials. However, accurate residue details of ligand induced protein binding and unfolding on an interface were still unknown by the current ensemble of protein structure characterizations. Here, a hydrogen/deuterium (H/D) approach coupled with analysis of NMR TOCSY spectra and the solvent accessible surface area (SASA) was designed to enable residue level understanding of lysozyme adsorbed at a phenyl-ligand modified surface. Results showed that the binding sites and unfolding of lysozyme molecules on phenyl-agarose microspheres demonstrated significant ligand-density dependence and protein-coverage dependence. Either increasing ligand density or decreasing adsorption coverage would lead to more binding sites and unfolding of the protein molecules. With the multipoint adsorption strengthening, the protein molecule changed from lying end-on to side-on. Finally, Molecular Dock simulation was utilized to evaluate the NMR determined binding sites based on energy ranking of the binding. It confirmed that this NMR approach represents a reliable route to in silico abundant residue-level structural information during protein interaction with biomaterials.Protein-ligand interactions on liquid-solid interfaces governed the design of functional biomaterials. However, accurate residue details of ligand induced protein binding and unfolding on an interface were still unknown by the current ensemble of protein structure characterizations. Here, a hydrogen/deuterium (H/D) approach coupled with analysis of NMR TOCSY spectra and the solvent accessible surface area (SASA) was designed to enable residue level understanding of lysozyme adsorbed at a phenyl-ligand modified surface. Results showed that the binding sites and unfolding of lysozyme molecules on phenyl-agarose microspheres demonstrated significant ligand-density dependence and protein-coverage dependence. Either increasing ligand density or decreasing adsorption coverage would lead to more binding sites and unfolding of the protein molecules. With the multipoint adsorption strengthening, the protein molecule changed from lying end-on to side-on. Finally, Molecular Dock simulation was utilized to evaluate the NMR determined binding sites based on energy ranking of the binding. It confirmed that this NMR approach represents a reliable route to in silico abundant residue-level structural information during protein interaction with biomaterials

Characterization of Gglycosaminoglycan (GAG) sulfatases from the human gut symbiont bacteroides thetaiotaomicron reveals the first GAG-specific bacterial endosulfatase

Background: Sulfatases are emerging as key adaptive tools of commensal bacteria to their host. Results: The first bacterial endo-O-sulfatase and three exo-O-sulfatases from the human commensal Bacteroides thetaiotaomicron, specific for glycosaminoglycans, have been discovered and characterized. Conclusion: Commensal bacteria possess a unique array of highly specific sulfatases to metabolize host glycans. Significance: Bacterial sulfatases are much more diverse than anticipated. Despite the importance of the microbiota in human physiology, the molecular bases that govern the interactions between these commensal bacteria and their host remain poorly understood. We recently reported that sulfatases play a key role in the adaptation of a major human commensal bacterium, Bacteroides thetaiotaomicron, to its host (Benjdia, A., Martens, E. C., Gordon, J. I., and Berteau, O. (2011) J. Biol. Chem. 286, 25973-25982). We hypothesized that sulfatases are instrumental for this bacterium, and related Bacteroides species, to metabolize highly sulfated glycans (i.e. mucins and glycosaminoglycans (GAGs)) and to colonize the intestinal mucosal layer. Based on our previous study, we investigated 10 sulfatase genes induced in the presence of host glycans. Biochemical characterization of these potential sulfatases allowed the identification of GAG-specific sulfatases selective for the type of saccharide residue and the attachment position of the sulfate group. Although some GAG-specific bacterial sulfatase activities have been described in the literature, we report here for the first time the identity and the biochemical characterization of four GAG-specific sulfatases. Furthermore, contrary to the current paradigm, we discovered that B. thetaiotaomicron possesses an authentic GAG endosulfatase that is active at the polymer level. This type of sulfatase is the first one to be identified in a bacterium. Our study thus demonstrates that bacteria have evolved more sophisticated and diverse GAG sulfatases than anticipated and establishes how B. thetaiotaomicron, and other major human commensal bacteria, can metabolize and potentially tailor complex host glycans