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Leiden, Netherlands

Van Melckebeke H.,ETH Zurich | Wasmer C.,ETH Zurich | Lange A.,ETH Zurich | Lange A.,Max Planck Institute for Biophysical Chemistry | And 5 more authors.
Journal of the American Chemical Society

We present a strategy to solve the high-resolution structure of amyloid fibrils by solid-state NMR and use it to determine the atomic-resolution structure of the prion domain of the fungal prion HET-s in its amyloid form. On the basis of 134 unambiguous distance restraints, we recently showed that HET-s(218-289) in its fibrillar state forms a left-handed β-solenoid, and an atomic-resolution NMR structure of the triangular core was determined from unambiguous restraints only. In this paper, we go considerably further and present a comprehensive protocol using six differently labeled samples, a collection of optimized solid-state NMR experiments, and adapted structure calculation protocols. The high-resolution structure obtained includes the less ordered but biologically important C-terminal part and improves the overall accuracy by including a large number of ambiguous distance restraints. © 2010 American Chemical Society. Source

Kappo M.A.,University of the Western Cape | Ab E.,ZoBio BV | Hassem F.,University of the Western Cape | Atkinson R.A.,Institute Of Genetique Et Of Biologie Moleculaire Et Cellulaire | And 9 more authors.
Journal of Biological Chemistry

Retinoblastoma-binding protein-6 (RBBP6) plays a facilitating role, through its RING finger-like domain, in the ubiquitination of p53 by Hdm2 that is suggestive of E4-like activity. Although the presence of eight conserved cysteine residues makes it highly probable that theRINGfinger-like domain coordinates two zinc ions, analysis of the primary sequence suggests an alternative classification as a member of the U-box family, the members of which do not bind zinc ions. We show here that despite binding two zinc ions, the domain adopts a homodimeric structure highly similar to those of a number of U-boxes. Zinc ions could be replaced by cadmium ions without significantly disrupting the structure or the stability of the domain, although the rate of substitution was an order of magnitude slower than any previous measurement, suggesting that the structure is particularly stable, a conclusion supported by the high thermal stability of the domain. A hallmark of U-box-containing proteins is their association with chaperones, with which they cooperate in eliminating irretrievably unfolded proteins by tagging them for degradation by the proteasome. Using a yeast two-hybrid screen, we show that RBBP6 interacts with chaperones Hsp70 and Hsp40 through its N-terminal ubiquitin-like domain. Taken together with the structural similarities to U-box-containing proteins, our data suggest that RBBP6 plays a role in chaperone-mediated ubiquitination and possibly in protein quality control. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A. Source

Kobayashi M.,ZoBio BV | Retra K.,VU University Amsterdam | Figaroa F.,ZoBio BV | Hollander J.G.,ZoBio BV | And 5 more authors.
Journal of Biomolecular Screening

Fragment-based drug discovery (FBDD) has become a widely accepted tool that is complementary to high-throughput screening (HTS) in developing small-molecule inhibitors of pharmaceutical targets. Because a fragment campaign can only be as successful as the hit matter found, it is critical that the first stage of the process be optimized. Here the authors compare the 3 most commonly used methods for hit discovery in FBDD: high concentration screening (HCS), solution ligand-observed nuclear magnetic resonance (NMR), and surface plasmon resonance (SPR). They selected the commonly used saturation transfer difference (STD) NMR spectroscopy and the proprietary target immobilized NMR screening (TINS) as representative of the array of possible NMR methods. Using a target typical of FBDD campaigns, the authors find that HCS and TINS are the most sensitive to weak interactions. They also find a good correlation between TINS and STD for tighter binding ligands, but the ability of STD to detect ligands with affinity weaker than 1 mM KD is limited. Similarly, they find that SPR detection is most suited to ligands that bind with KD better than 1 mM. However, the good correlation between SPR and potency in a bioassay makes this a good method for hit validation and characterization studies. © 2010 Society for Laboratory Automation and Screening. Source

Chen D.,ZoBio BV | Errey J.C.,Heptares Therapeutics | Heitman L.H.,Leiden University | Marshall F.H.,Heptares Therapeutics | And 3 more authors.
ACS Chemical Biology

Fragment-based drug discovery (FBDD) has proven a powerful method to develop novel drugs with excellent oral bioavailability against challenging pharmaceutical targets such as protein-protein interaction targets. Very recently the underlying biophysical techniques have begun to be successfully applied to membrane proteins. Here we show that novel, ligand efficient small molecules with a variety of biological activities can be found by screening a small fragment library using thermostabilized (StaR) G protein-coupled receptors (GPCRs) and target immobilized NMR screening (TINS). Detergent-solubilized StaR adenosine A2A receptor was immobilized with retention of functionality, and a screen of 531 fragments was performed. Hits from the screen were thoroughly characterized for biochemical activity using the wild-type receptor. Both orthosteric and allosteric modulatory activity has been demonstrated in biochemical validation assays. Allosteric activity was confirmed in cell-based functional assays. The validated fragment hits make excellent starting points for a subsequent hit-to-lead elaboration program. © 2012 American Chemical Society. Source

Chen D.,ZoBio BV | Ranganathan A.,Science for Life Laboratory | Ranganathan A.,University of Stockholm | Ijzerman A.P.,Leiden University | And 4 more authors.
Journal of Chemical Information and Modeling

Fragment-based lead discovery (FBLD) is becoming an increasingly important method in drug development. We have explored the potential to complement NMR-based biophysical screening of chemical libraries with molecular docking in FBLD against the A2A adenosine receptor (A2AAR), a drug target for inflammation and Parkinson's disease. Prior to an NMR-based screen of a fragment library against the A2AAR, molecular docking against a crystal structure was used to rank the same set of molecules by their predicted affinities. Molecular docking was able to predict four out of the five orthosteric ligands discovered by NMR among the top 5% of the ranked library, suggesting that structure-based methods could be used to prioritize among primary hits from biophysical screens. In addition, three fragments that were top-ranked by molecular docking, but had not been picked up by the NMR-based method, were demonstrated to be A2AAR ligands. While biophysical approaches for fragment screening are typically limited to a few thousand compounds, the docking screen was extended to include 328,000 commercially available fragments. Twenty-two top-ranked compounds were tested in radioligand binding assays, and 14 of these were A2AAR ligands with Ki values ranging from 2 to 240 μM. Optimization of fragments was guided by molecular dynamics simulations and free energy calculations. The results illuminate strengths and weaknesses of molecular docking and demonstrate that this method can serve as a valuable complementary tool to biophysical screening in FBLD. © 2013 American Chemical Society. Source

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