Identification of a novel human polyomavirus in organs of the gastrointestinal tract

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Organocatalytic access to a cis-Cyclopentyl-gamma-amino acid: an intriguing model of selectivity and formation of a stable 10/12-helix from the corresponding gamma/alpha-peptide

In this study, we have developed a highly enantioselective organocatalytic route to the (1S,2R)-2-(aminomethyl)cyclopentane-1-carboxylic acid monomer precursor, which has a cis-configuration between the C- and N-termini around the cyclopentane core. Kinetic measurements show that the product distribution changes over time due to epimerization of the C1 center. Computations suggest the cis-selectivity is a result of selective C-C bond formation, whilst subsequent steps appear to infuence the selectivity at higher temperature. The resulting gamma-amino acid residue was incorporated into a novel gamma/alpha-peptide which forms a well-ordered 10/12-helix with alternate H-bond directionality in spite of the smallest value of the zeta-angle yet observed for a helix of this type. This highly dened structure is a result of the narrow range of potential zeta-angles in our monomer. In contrast, the larger range of potential zeta-values observed for the corresponding trans-system can be fulfilled by several competing helical structures

It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods

Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein alpha-subunits (G alpha*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction-diffusion simulations. G alpha* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of G alpha* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 G alpha*. PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that G alpha*. PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of G alpha* which binds with lower affinity, forming G alpha*. PDE6. G alpha*. Reaction-diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of G alpha* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated G alpha* fails to activate the effector enzyme.This work was funded by Deutsche Forschungsgemeinschaftthrough grant nos. SP 1130/1-1 and SFB 449 to M.H., K.P.H. andC.M.T.S., SFB 740 to F.N., M.H., K.P.H., T.M. and C.M.T.S., a EuropeanResearch Council starting grant (pcCell) to F.N. and a EuropeanResearch Council advanced grant (TUDOR) to K.P.H. E.B. holds aFreigeist-Fellowship from the Volkswagen Foundatio

Inhibition of cathepsin G by 2-amino-3,1-benzoxazin-4-ones: Kinetic investigations and docking studies

A series of benzoxazinones was used to investigate the interaction of human cathepsin G with acyl-enzyme inhibitors. With respect to the primary specificity of cathepsin G, inhibitors with hydrophobic or basic residues at position 2 were included in the study. Parameters of the enzyme acylation and deacylation were determined by slow-binding kinetics in the presence of a chromogenic substrate. For selected inhibitors, the time course of the enzyme-catalyzed conversion of the inhibitors was followed. This approach was suitable to elucidate a rate-determining deacylation step. Docking simulations of the noncovalent enzymeinhibitor complexes were performed and several clusters were analyzed for each inhibitor. The amino acids of the active site that participate in the binding of the inhibitors were determined. The arrangements in several clusters of an inhibitor were not uniform with respect to the orientation by which the inhibitor was bound in the S1 pocket. Docking of the basic piperazino derivatives 6 and 10 indicated an interaction with Glu 226 at the bottom of the S1 specificity pocket. The (N-methyl)benzylamino derivative 1 showed the strongest acylation rate ðkon ¼ 1200M1 s1Þ, which was attributed to a high extent of pseudo-productive orientations of the noncovalent preassociation complex

First Crystal Structures of alpha,delta-Peptidic Foldamers and Solution State NMR Show an Unusual 13/11 Helix: Rational Design and Application as a Minimalist Aldolase Mimic

We report the first structures of an unusual 13/11-helix (alternating i,i+1 {NH--O=C} and i,i+3 {C=O--H—N} H-bonds) formed by a heteromeric 1:1 se-quence of alpha- and delta-amino acids, using both XRD and NMR. Whilst intramolecular hydrogen bonds (IMHBs) are the clear driver of helix formation, we also observe an apolar interaction between the ethyl residue of one delta-amino acid and the cyclohexyl group of the next delta-residue in the sequence that seems to stabilize one type of helix over another. Using this structural information, we have inserted two ornithine residues within the helix to install bis-amine functionality. The resulting foldamer acts as a minimalistic aldolase mimic

ERAP1 allotypes impact the epitope repertoire of virus-specific CD8+ T cell responses in acute hepatitis C virus infection

Background & Aims Endoplasmic reticulum aminopeptidase 1 (ERAP1) polymorphisms are linked with human leukocyte antigen (HLA) class I-associated autoinflammatory disorders, including ankylosing spondylitis and Behçet’s disease. Disease-associated ERAP1 allotypes exhibit distinct functional properties, but it remains unclear how differential peptide trimming in vivo affects the repertoire of epitopes presented to CD8+ T cells. The aim of this study was to determine the impact of ERAP1 allotypes on the virus-specific CD8+ T cell epitope repertoire in an HLA-B*27:05+ individual with acute hepatitis C virus (HCV) infection. Methods We performed genetic and functional analyses of ERAP1 allotypes and characterized the HCV-specific CD8+ T cell repertoire at the level of fine epitope specificity and HLA class I restriction. Results Two hypoactive allotypic variants of ERAP1 were identified in an individual with acute HCV infection. The associated repertoire of virus-derived epitopes recognized by CD8+ T cells was uncommon in two respects. First, reactivity was directed away from classically immunodominant epitopes, preferentially targeting either novel or subdominant epitopes. Second, reactivity was biased towards longer epitopes (10–11mers). Despite the presence of favorable prognostic indicators, these atypical immune responses failed to clear HCV. Conclusions ERAP1 allotypes modify the virus-specific CD8+ T cell epitope repertoire in vivo, leading to altered immunodominance patterns that may contribute to the failure of antiviral immunity after infection with HCV. Lay summary Endoplasmic reticulum aminopeptidase 1 (ERAP1) plays a key role in antigen presentation. Genetic variants of ERAP1 are linked with human leukocyte antigen (HLA) class I-associated autoinflammatory disorders, such as ankylosing spondylitis and Behçet’s disease, but it remains unclear how these functionally distinct allotypes influence the repertoire of epitopes presented to CD8+ T cells. We found that ERAP1 allotypes can modify the virus-specific CD8+ T cell epitope repertoire in vivo, leading to altered immunodominance patterns that may contribute to the failure of antiviral immunity after infection with hepatitis C virus (HCV)

Multiple Synchronous Outbreaks of Puumala Virus, Germany, 2010

To investigate 2,017 cases of hantavirus disease in Germany, we compared 38 new patient-derived Puumala virus RNA sequences identified in 2010 with bank vole–derived small segment RNA sequences. The epidemic process was driven by outbreaks of 6 Puumala virus clades comprising strains of human and vole origin. Each clade corresponded to a different outbreak region