| 1. |
- Bach, Anders, et al.
(författare)
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A high-affinity, dimeric inhibitor of PSD-95 bivalently interacts with PDZ1-2 and protects against ischemic brain damage
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:9, s. 3317-3322
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Tidskriftsartikel (refereegranskat)abstract
- Inhibition of the ternary protein complex of the synaptic scaffolding protein postsynaptic density protein-95 (PSD-95), neuronal nitric oxide synthase (nNOS), and the N-methyl-D-aspartate (NMDA) receptor is a potential strategy for treating ischemic brain damage, but high-affinity inhibitors are lacking. Here we report the design and synthesis of a novel dimeric inhibitor, Tat-NPEG4(IETDV)(2) (Tat-N-dimer), which binds the tandem PDZ1-2 domain of PSD-95 with an unprecedented high affinity of 4.6 nM, and displays extensive protease-resistance as evaluated in vitro by stability-measurements in human blood plasma. X-ray crystallography, NMR, and small-angle X-ray scattering (SAXS) deduced a true bivalent interaction between dimeric inhibitor and PDZ1-2, and also provided a dynamic model of the conformational changes of PDZ1-2 induced by the dimeric inhibitor. A single intravenous injection of Tat-N-dimer (3 nmol/g) to mice subjected to focal cerebral ischemia reduces infarct volume with 40% and restores motor functions. Thus, Tat-N-dimer is a highly efficacious neuroprotective agent with therapeutic potential in stroke.
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| 2. |
- Chi, Celestine N., 1978-, et al.
(författare)
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Biophysical Characterization of the Complex between Human Papillomavirus E6 Protein and Synapse-associated Protein 97
- 2011
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Ingår i: Journal of Biological Chemistry. - : The American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 286:5, s. 3597-3606
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Tidskriftsartikel (refereegranskat)abstract
- The E6 protein of human papillomavirus (HPV) exhibits complex interaction patterns with several host proteins, and their roles in HPV-mediated oncogenesis have proved challenging to study. Here we use several biophysical techniques to explore the binding of E6 to the three PDZ domains of the tumor suppressor protein synapse-associated protein 97 (SAP97). All of the potential binding sites in SAP97 bind E6 with micromolar affinity. The dissociation rate constants govern the different affinities of HPV16 and HPV18 E6 for SAP97. Unexpectedly, binding is not mutually exclusive, and all three PDZ domains can simultaneously bind E6. Intriguingly, this quaternary complex has the same apparent hydrodynamic volume as the unliganded PDZ region, suggesting that a conformational change occurs in the PDZ region upon binding, a conclusion supported by kinetic experiments. Using NMR, we discovered a new mode of interaction between E6 and PDZ: a subset of residues distal to the canonical binding pocket in the PDZ(2) domain exhibited noncanonical interactions with the E6 protein. This is consistent with a larger proportion of the protein surface defining binding specificity, as compared with that reported previously.
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| 3. |
- Chi, Celestine N., et al.
(författare)
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Ligand binding by PDZ domains
- 2012
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Ingår i: Biofactors. - : Wiley. - 0951-6433 .- 1872-8081. ; 38:5, s. 338-348
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Forskningsöversikt (refereegranskat)abstract
- The postsynaptic density protein-95/disks large/zonula occludens-1 (PDZ) protein domain family is one of the most common proteinprotein interaction modules in mammalian cells, with paralogs present in several hundred human proteins. PDZ domains are found in most cell types, but neuronal proteins, for example, are particularly rich in these domains. The general function of PDZ domains is to bring proteins together within the appropriate cellular compartment, thereby facilitating scaffolding, signaling, and trafficking events. The many functions of PDZ domains under normal physiological as well as pathological conditions have been reviewed recently. In this review, we focus on the molecular details of how PDZ domains bind their protein ligands and their potential as drug targets in this context.
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| 4. |
- Eildal, Jonas N. N., et al.
(författare)
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Probing the Role of Backbone Hydrogen Bonds in Protein-Peptide Interactions by Amide-to-Ester Mutations
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:35, s. 12998-13007
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Tidskriftsartikel (refereegranskat)abstract
- One of the most frequent protein-protein interaction modules in mammalian cells is the postsynaptic density 95/discs large/zonula occludens 1 (PDZ) domain, involved in scaffolding and signaling and emerging as an important drug target for several diseases. Like many other protein-protein interactions, those of the PDZ domain family involve formation of intermolecular hydrogen bonds: C-termini or internal linear motifs of proteins bind as beta-strands to form an extended antiparallel beta-sheet with the PDZ domain. Whereas extensive work has focused on the importance of the, amino acid side chains of the protein ligand, the role of the backbone hydrogen bonds in the binding reaction is not known. Using amide-to-ester substitutions to perturb the backbone hydrogen-bonding pattern, we have systematically probed putative backbone hydrogen bonds between four different PDZ domains and peptides corresponding to natural protein ligands. Amide-to-ester mutations of the three C-terminal amides of the peptide ligand severely affected the affinity with the PDZ domain, demonstrating that hydrogen bonds contribute significantly to ligand binding (apparent changes in binding energy, Delta Delta G = 1.3 to >3.8 kcal mol(-1)). This decrease in affinity was mainly due to an increase in the dissociation rate constant, but a significant decrease in the association rate constant was found for some amide-to-ester mutations Suggesting that native hydrogen bonds have begun to form in the transition state of the binding reaction. This study provides a general framework for studying the role of backbone hydrogen bonds in protein-peptide interactions and for the first time specifically addresses these for PDZ domain-peptide interactions.
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| 5. |
- Eildal, Jonas N. N., et al.
(författare)
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Rigidified Clicked Dimeric Ligands for Studying the Dynamics of the PDZ1-2 Supramodule of PSD-95
- 2015
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 16:1, s. 64-69
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Tidskriftsartikel (refereegranskat)abstract
- PSD-95 is a scaffolding protein of the MAGUK protein family, and engages in several vital protein-protein interactions in the brain with its PDZ domains. It has been suggested that PSD-95 is composed of two supramodules, one of which is the PDZ1-2 tandem domain. Here we have developed rigidified high-affinity dimeric ligands that target the PDZ1-2 supramodule, and established the biophysical parameters of the dynamic PDZ1-2/ligand interactions. By employing ITC, protein NMR, and stopped-flow kinetics this study provides a detailed insight into the overall conformational energetics of the interaction between dimeric ligands and tandem PDZ domains. Our findings expand our understanding of the dynamics of PSD-95 with potential relevance to its biological role in interacting with multivalent receptor complexes and development of novel drugs.
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| 6. |
- Haq, S Raza, et al.
(författare)
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Side-Chain Interactions Form Late and Cooperatively in the Binding Reaction between Disordered Peptides and PDZ Domains
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 134:1, s. 599-605
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Tidskriftsartikel (refereegranskat)abstract
- Intrinsically disordered proteins are very common and mediate numerous protein-protein and protein-DNA interactions. While it is clear that these interactions are instrumental for the life of the mammalian cell, there is a paucity of data regarding their molecular binding mechanisms. Here we have used short peptides as a model system for intrinsically disordered proteins. Linear free energy relationships based on rate and equilibrium constants for the binding of these peptides to ordered target proteins, PDZ domains, demonstrate that native side-chain interactions form mainly after the rate-limiting barrier for binding and in a cooperative fashion. This finding suggests that these disordered peptides first form a weak encounter complex with non-native interactions. The data do not support the recent notion that the affinities of intrinsically disordered proteins toward their targets are generally governed by their association rate constants. Instead, we observed the opposite for peptide-PDZ interactions, namely, that changes in K-d correlate with changes in k(off).
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| 7. |
- Nissen, Klaus B., et al.
(författare)
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Targeting Protein-Protein Interactions with Trimeric Ligands : High Affinity Inhibitors of the MAGUK Protein Family
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- PDZ domains in general, and those of PSD-95 in particular, are emerging as promising drug targets for diseases such as ischemic stroke. We have previously shown that dimeric ligands that simultaneously target PDZ1 and PDZ2 of PSD-95 are highly potent inhibitors of PSD-95. However, PSD-95 and the related MAGUK proteins contain three consecutive PDZ domains, hence we envisioned that targeting all three PDZ domains simultaneously would lead to more potent and potentially more specific interactions with the MAGUK proteins. Here we describe the design, synthesis and characterization of a series of trimeric ligands targeting all three PDZ domains of PSD-95 and the related MAGUK proteins, PSD93, SAP-97 and SAP-102. Using our dimeric ligands targeting the PDZ1-2 tandem as starting point, we designed novel trimeric ligands by introducing a PDZ3-binding peptide moiety via a cysteine-derivatized NPEG linker. The trimeric ligands generally displayed increased affinities compared to the dimeric ligands in fluorescence polarization binding experiments and optimized trimeric ligands showed low nanomolar inhibition towards the four MAGUK proteins, thus being the most potent inhibitors described. Kinetic experiments using stopped-flow spectrometry showed that the increase in affinity is caused by a decrease in the dissociation rate of the trimeric ligand as compared to the dimeric ligands, likely reflecting the lower probability of simultaneous dissociation of all three PDZ ligands. Thus, we have provided novel inhibitors of the MAGUK proteins with exceptionally high affinity, which can be used to further elucidate the therapeutic potential of these proteins.
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| 8. |
- Pedersen, Soren W., et al.
(författare)
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Probing backbone hydrogen bonding in PDZ/ligand interactions by protein amide-to-ester mutations
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5, s. 3215-
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Tidskriftsartikel (refereegranskat)abstract
- PDZ domains are scaffolding modules in protein-protein interactions that mediate numerous physiological functions by interacting canonically with the C-terminus or non-canonically with an internal motif of protein ligands. A conserved carboxylate-binding site in the PDZ domain facilitates binding via backbone hydrogen bonds; however, little is known about the role of these hydrogen bonds due to experimental challenges with backbone mutations. Here we address this interaction by generating semisynthetic PDZ domains containing backbone amide-to-ester mutations and evaluating the importance of individual hydrogen bonds for ligand binding. We observe substantial and differential effects upon amide-to-ester mutation in PDZ2 of postsynaptic density protein 95 and other PDZ domains, suggesting that hydrogen bonding at the carboxylate-binding site contributes to both affinity and selectivity. In particular, the hydrogen-bonding pattern is surprisingly different between the non-canonical and canonical interaction. Our data provide a detailed understanding of the role of hydrogen bonds in protein-protein interactions.
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| 9. |
- Pedersen, Soren W., et al.
(författare)
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The Role of Backbone Hydrogen Bonds in the Transition State for Protein Folding of a PDZ Domain
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:4, s. e95619-
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Tidskriftsartikel (refereegranskat)abstract
- Backbone hydrogen bonds are important for the structure and stability of proteins. However, since conventional site-directed mutagenesis cannot be applied to perturb the backbone, the contribution of these hydrogen bonds in protein folding and stability has been assessed only for a very limited set of small proteins. We have here investigated effects of five amide-to-ester mutations in the backbone of a PDZ domain, a 90-residue globular protein domain, to probe the influence of hydrogen bonds in a b-sheet for folding and stability. The amide-to-ester mutation removes NH-mediated hydrogen bonds and destabilizes hydrogen bonds formed by the carbonyl oxygen. The overall stability of the PDZ domain generally decreased for all amide-to-ester mutants due to an increase in the unfolding rate constant. For this particular region of the PDZ domain, it is therefore clear that native hydrogen bonds are formed after crossing of the rate-limiting barrier for folding. Moreover, three of the five amide-to-ester mutants displayed an increase in the folding rate constant suggesting that the hydrogen bonds are involved in non-native interactions in the transition state for folding.
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| 10. |
- Sereikaite, Vita, et al.
(författare)
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Probing Backbone Hydrogen Bonds in Proteins by Amide-to-Ester Mutations
- 2018
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Ingår i: ChemBioChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4227 .- 1439-7633. ; 19:20, s. 2136-2145
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Forskningsöversikt (refereegranskat)abstract
- All proteins contain characteristic backbones formed of consecutive amide bonds, which can engage in hydrogen bonds. However, the importance of these is not easily addressed by conventional technologies that only allow for side-chain substitutions. By contrast, technologies such as nonsense suppression mutagenesis and protein ligation allow for manipulation of the protein backbone. In particular, replacing the backbone amide groups with ester groups, that is, amide-to-ester mutations, is a powerful tool to examine backbone-mediated hydrogen bonds. In this minireview, we showcase examples of how amide-to-ester mutations can be used to uncover pivotal roles of backbone-mediated hydrogen bonds in protein recognition, folding, function, and structure.
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