| 1. |
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| 2. |
- Geitmann, Matthis, et al.
(författare)
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Identification of a Novel Scaffold for Allosteric Inhibition of Wild Type and Drug Resistant HIV-1 Reverse Transcriptase by Fragment Library Screening
- 2011
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 54:3, s. 699-708
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Tidskriftsartikel (refereegranskat)abstract
- A novel scaffold inhibiting wild type and drug resistant variants of human immunodeficiency virus type 1 reverse transcriptase (HIV-1RT) has been identified in a library consisting of 1040 fragments. The fragments were significantly different from already known non-nucleoside reverse transcriptase inhibitors (NNRTIs), as indicated by a Tversky similarity analysis. A screening strategy involving SPR biosensor-based interaction analysis and enzyme inhibition was used. Primary biosensor-based screening, using short concentration series, was followed by analysis of nevirapine competition and enzyme inhibition, thus identifying inhibitory fragments binding to the non-nucleoside reverse transcriptase inhibitor (NNRTI) binding site. Ten hits were discovered, and their affinities and resistance profiles were evaluated with wild type and three drug resistant enzyme variants (K103N, Y181C, and L100I). One fragment exhibited submillimolar K(D) and IC(50) values against all four tested enzyme variants. A substructure comparison between the fragment and 826 structurally diverse published NNRTIs confirmed that the scaffold was novel. The fragment is a bromoindanone with a ligand efficiency of 0.42 kcal/mol(-1).
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| 3. |
- Gorny, Xenia, et al.
(författare)
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AKAP79/150 interacts with the neuronal calcium-binding protein caldendrin
- 2012
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Ingår i: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 122:4, s. 714-726
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Tidskriftsartikel (refereegranskat)abstract
- The A kinase-anchoring protein AKAP79/150 is a postsynaptic scaffold molecule and a key regulator of signaling events. At the postsynapse it coordinates phosphorylation and dephosphorylation of receptors via anchoring kinases and phosphatases near their substrates. Interactions between AKAP79 and two Ca2+ -binding proteins caldendrin and calmodulin have been investigated here. Calmodulin is a known interaction partner of AKAP79/150 that has been shown to regulate activity of the kinase PKC in a Ca2+-dependent manner. Pull-down experiments and surface plasmon resonance biosensor analyses have been used here to demonstrate that AKAP79 can also interact with caldendrin, a neuronal calcium-binding protein implicated in regulation of Ca2+ -influx and release. We demonstrate that calmodulin and caldendrin compete for a partially overlapping binding site on AKAP79 and that their binding is differentially dependent on calcium. Therefore, this competition is regulated by calcium levels. Moreover, both proteins have different binding characteristics suggesting that the two proteins might play complementary roles. The postsynaptic enrichment, the complex binding mechanism, and the competition with calmodulin, makes caldendrin an interesting novel player in the signaling toolkit of the AKAP interactome.
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| 4. |
- Huang, Hsin-Ho, et al.
(författare)
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Analysis of the leakage of gene repression by an artificial TetR-regulated promoter in cyanobacteria
- 2015
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Ingår i: BMC Research Notes. - : Springer Science and Business Media LLC. - 1756-0500. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: There is a need for strong and tightly regulated promoters to construct more reliable and predictable genetic modules for synthetic biology and metabolic engineering. For this reason we have previously constructed a TetR regulated L promoter library for the cyanobacterium Synechocystis PCC 6803. In addition to the L03 promoter showing wide dynamic range of transcriptional regulation, we observed the L09 promoter as unique in high leaky gene expression under repressed conditions. In the present study, we attempted to identify the cause of L09 promoter leakage. TetR binding to the promoter was studied by theoretical simulations of DNA breathing dynamics and by surface plasmon resonance (SPR) biosensor technology to analyze the kinetics of the DNA-protein interactions.RESULTS: DNA breathing dynamics of a promoter was computed with the extended nonlinear Peyrard-Bishop-Dauxois mesoscopic model to yield a DNA opening probability profile at a single nucleotide resolution. The L09 promoter was compared to the L10, L11, and L12 promoters that were point-mutated and different in repressed promoter strength. The difference between DNA opening probability profiles is trivial on the TetR binding site. Furthermore, the kinetic rate constants of TetR binding, as measured by SPR biosensor technology, to the respective promoters are practically identical. This suggests that a trivial difference in probability as low as 1 × 10(-4) cannot lead to detectable variations in the DNA-protein interactions. Higher probability at the downstream region of transcription start site of the L09 promoter compared to the L10, L11, and L12 promoters was observed. Having practically the same kinetics of binding to TetR, the leakage problem of the L09 promoter might be due to enhanced RNA Polymerase (RNAP)-promoter interactions in the downstream region.CONCLUSIONS: Both theoretical and experimental analyses of the L09 promoter's leakage problem exclude a mechanism of reduced TetR binding but instead suggest enhanced RNAP binding. These results assist in creating more tightly regulated promoters for realizing synthetic biology and metabolic engineering in biotechnological applications.
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| 5. |
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| 6. |
- Pandya, Nikhil J, et al.
(författare)
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Noelin1 Affects Lateral Mobility of Synaptic AMPA Receptors
- 2018
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 24:5, s. 1218-1230
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Tidskriftsartikel (refereegranskat)abstract
- Lateral diffusion on the neuronal plasma membrane of the AMPA-type glutamate receptor (AMPAR) serves an important role in synaptic plasticity. We investigated the role of the secreted glycoprotein Noelin1 (Olfactomedin-1 or Pancortin) in AMPAR lateral mobility and its dependence on the extracellular matrix (ECM). We found that Noelin1 interacts with the AMPAR with high affinity, however, without affecting rise- and decay time and desensitization properties. Noelin1 co-localizes with synaptic and extra-synaptic AMPARs and is expressed at synapses in an activity-dependent manner. Single-particle tracking shows that Noelin1 reduces lateral mobility of both synaptic and extra-synaptic GluA1-containing receptors and affects short-term plasticity. While the ECM does not constrain the synaptic pool of AMPARs and acts only extrasynaptically, Noelin1 contributes to synaptic potentiation by limiting AMPAR mobility at synaptic sites. This is the first evidence for the role of a secreted AMPAR-interacting protein on mobility of GluA1-containing receptors and synaptic plasticity.
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| 7. |
- Seeger, Christian, 1982-, et al.
(författare)
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Biophysical analysis of the dynamics of calmodulin interactions with neurogranin and Ca2+/calmodulin-dependent kinase II
- 2017
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Ingår i: Journal of Molecular Recognition. - : Wiley. - 0952-3499 .- 1099-1352. ; 30, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Calmodulin (CaM) functions depend on interactions with CaM-binding proteins, regulated by Ca2+. Induced structural changes influence the affinity, kinetics, and specificities of the interactions. The dynamics of CaM interactions with neurogranin (Ng) and the CaM-binding region of Ca2+/calmodulin-dependent kinase II (CaMKII290-309) have been studied using biophysical methods. These proteins have opposite Ca2+ dependencies for CaM binding. Surface plasmon resonance biosensor analysis confirmed that Ca2+ and CaM interact very rapidly, and with moderate affinity (KDSPR=3M). Calmodulin-CaMKII290-309 interactions were only detected in the presence of Ca2+, exhibiting fast kinetics and nanomolar affinity (KDSPR7.1nM). The CaM-Ng interaction had higher affinity under Ca2+-depleted (KDSPR480nM,3.4x105M-1s-1 and k(-1) = 1.6 x 10(-1)s(-1)) than Ca2+-saturated conditions (KDSPR19M). The IQ motif of Ng (Ng(27-50)) had similar affinity for CaM as Ng under Ca2+-saturated conditions (KDSPR=14M), but no interaction was seen under Ca2+-depleted conditions. Microscale thermophoresis using fluorescently labeled CaM confirmed the surface plasmon resonance results qualitatively, but estimated lower affinities for the Ng (KDMST890nM) and CaMKII290-309(KDMST190nM) interactions. Although CaMKII290-309 showed expected interaction characteristics, they may be different for full-length CaMKII. The data for full-length Ng, but not Ng(27-50), agree with the current model on Ng regulation of Ca2+/CaM signaling.
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| 8. |
- Seeger, Christian, et al.
(författare)
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Histaminergic pharmacology of homo-oligomeric beta 3 gamma-aminobutyric acid type A receptors characterized by surface plasmon resonance biosensor technology
- 2012
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Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952 .- 1356-1839. ; 84:3, s. 341-351
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Tidskriftsartikel (refereegranskat)abstract
- A surface plasmon resonance biosensor assay was established for studying the interactions of 51 histaminergic and 15 GABAergic ligands with homo-oligomeric beta 3 GABA(A) receptors. Detergent solubilized receptors were successfully immobilized via affinity-capture on biosensor surfaces. The interaction kinetics of both histaminergic and GABAergic ligands were very rapid but affinities could be determined by steady-state analysis. Binding of several GABAergic ligands was observed, in agreement with previous data. Histamine and 16 histaminergic ligands were detected to directly bind to beta 3 GABA(A) receptors with micromolar affinity (K-D <300 mu M), thus extending previous evidence that beta 3 GABA(A) receptors can interact with histaminergic ligands. Histamine exhibited an affinity for these receptors comparable to that for human histamine type 1 (H1) or type 2 (H2) receptors. Furthermore, 13 of these histaminergic ligands appeared to compete with histamine. The discovery that H2, H3 and H4 receptor ligands interact with beta 3 receptors indicates a unique histaminergic pharmacology of these receptors. Due to their low affinity for the homo-pentameric beta 3 receptors these histaminergic drugs are not expected to modulate these receptors at clinically relevant concentrations. The results support the use of the new biosensor assay for the identification of drugs interacting with full length receptors and for fragment-based drug discovery of high affinity ligands for beta 3 receptors. Drugs with high affinity and selectivity for these receptors can be used to clarify the question whether beta 3 receptors do exist in the brain, and provide new avenues for the development of therapeutically active compounds targeting this novel histamine binding site.
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| 9. |
- Seeger, Christian, et al.
(författare)
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Kinetic and mechanistic differences in the interactions between caldendrin and calmodulin with AKAP79 suggest different roles in synaptic function
- 2012
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Ingår i: Journal of Molecular Recognition. - : Wiley. - 0952-3499 .- 1099-1352. ; 25:10, s. 495-503
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Tidskriftsartikel (refereegranskat)abstract
- The kinetic and mechanistic details of the interaction between caldendrin, calmodulin and the B-domain of AKAP79 were determined using a biosensor-based approach. Caldendrin was found to compete with calmodulin for binding at AKAP79, indicating overlapping binding sites. Although the AKAP79 affinities were similar for caldendrin (KD?=?20?n m) and calmodulin (KD?=?30?n m), their interaction characteristics were different. The calmodulin interaction was well described by a reversible one-step model, but was only detected in the presence of Ca2+. Caldendrin interacted with a higher level of complexity, deduced to be an induced fit mechanism with a slow relaxation back to the initial encounter complex. It interacted with AKAP79 also in the absence of Ca2+, but with different kinetic rate constants. The data are consistent with a similar initial Ca2+-dependent binding step for the two proteins. For caldendrin, a second Ca2+-independent rearrangement step follows, resulting in a stable complex. The study shows the importance of establishing the mechanism and kinetics of proteinprotein interactions and that minor differences in the interaction of two homologous proteins can have major implications in their functional characteristics. These results are important for the further elucidation of the roles of caldendrin and calmodulin in synaptic function.
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| 10. |
- Seeger, Christian, 1982-
(författare)
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Revealing Secrets of Synaptic Protein Interactions : A Biosensor based Strategy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein interactions are the basis of synaptic function, and studying these interactions on a molecular level is crucial for understanding basic brain function, as well as mechanisms underlying neurological disorders. In this thesis, kinetic and mechanistic characterization of synaptic protein interactions was performed by using surface plasmon resonance biosensor technology. Fragment library screening against the reverse transcriptase of HIV was included, as it served as an outlook for future drug discovery against ligand-gated ion channels.The protein-protein interaction studies of postsynaptic Ca2+ -binding proteins revealed caldendrin as a novel binding partner of AKAP79. Caldendrin and calmodulin bind and compete at similar binding sites but their interactions display different mechanisms and kinetics. In contrast to calmodulin, caldendrin binds to AKAP79 both in the presence and absence of Ca2+ suggesting distinct in vivo functional properties of caldendrin and calmodulin.Homo-oligomeric β3 GABAA receptors, although not yet identified in vivo, are candidates for a histamine-gated ion channel in the brain. To aid the identification of the receptor, 51 histaminergic ligands were screened and a unique pharmacology was determined. A further requirement for identifying β3 receptors in the brain, is the availability of specific high-affinity ligands. The developed biosensor assay displayed sufficient sensitivity and throughput for screening for such ligands, as well as for being employed for fragment-based drug discovery.AMPA receptors are excitatory ligand-gated ion channels, involved in synaptic plasticity, and modulated by auxiliary proteins. Previous results have indicated that Noelin1, a secreted glycoprotein, interacts with the AMPA receptor. By using biochemical methods, it was shown that Noelin1 interacts directly with the receptor. The kinetics of the interaction were estimated by biosensor analysis, thereby confirming the interaction and suggesting low nanomolar affinity. The results provide a basis for functional characterization of a novel AMPA receptor protein interaction.The results demonstrate how secrets of synaptic protein interactions and function were revealed by using a molecular based approach. Improving the understanding of such interactions is valuable for basic neuroscience. At the same time, the technical advancements that were achieved to study interactions of ligand-gated ion channels by surface plasmon resonance technology, provide an important tool for discovery of novel therapeutics against these important drug targets.
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