FMP Publications

Our publications are recorded in a searchable database since 2010, updates will be added regularly.

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References
Structural analysis of a signal peptide inside the ribosome tunnel by DNP MAS NMR
Lange, S., Franks, W. T., Rajagopalan(*), N., Döring(*), K., Geiger, M. A., Linden, A., van Rossum, B. J., Kramer(*), G., Bukau(*), B.; Oschkinat, H.
Sci Adv, 2:e1600379
(2016)

Tags: NMR-Supported Structural Biology (Oschkinat), Molecular Biophysics (Lange, A.)

Abstract: Proteins are synthesized in cells by ribosomes and, in parallel, prepared for folding or targeting. While ribosomal protein synthesis is progressing, the nascent chain exposes amino-terminal signal sequences or transmembrane domains that mediate interactions with specific interaction partners, such as the signal recognition particle (SRP), the SecA-adenosine triphosphatase, or the trigger factor. These binding events can set the course for folding in the cytoplasm and translocation across or insertion into membranes. A distinction of the respective pathways depends largely on the hydrophobicity of the recognition sequence. Hydrophobic transmembrane domains stabilize SRP binding, whereas less hydrophobic signal sequences, typical for periplasmic and outer membrane proteins, stimulate SecA binding and disfavor SRP interactions. In this context, the formation of helical structures of signal peptides within the ribosome was considered to be an important factor. We applied dynamic nuclear polarization magic-angle spinning nuclear magnetic resonance to investigate the conformational states of the disulfide oxidoreductase A (DsbA) signal peptide stalled within the exit tunnel of the ribosome. Our results suggest that the nascent chain comprising the DsbA signal sequence adopts an extended structure in the ribosome with only minor populations of helical structure.

Tubular Epithelial NF-kappaB Activity Regulates Ischemic AKI
Marko(*), L., Vigolo(*), E., Hinze(*), C., Park(*), J. K., Roel(*), G., Balogh(*), A., Choi(*), M., Wübken(*), A., Cording, J., Blasig, I. E., Luft(*), F. C., Scheidereit(*), C., Schmidt-Ott(*), K. M., Schmidt-Ullrich(*), R.; Müller(*), D. N.
Journal of the American Society of Nephrology : JASN, 27:2658-2669
(2016)

Tags: Molecular Cell Physiology (Blasig, I.E.)

Abstract: NF-kappaB is a key regulator of innate and adaptive immunity and is implicated in the pathogenesis of AKI. The cell type-specific functions of NF-kappaB in the kidney are unknown; however, the pathway serves distinct functions in immune and tissue parenchymal cells. We analyzed tubular epithelial-specific NF-kappaB signaling in a mouse model of ischemia-reperfusion injury (IRI)-induced AKI. NF-kappaB reporter activity and nuclear localization of phosphorylated NF-kappaB subunit p65 analyses in mice revealed that IRI induced widespread NF-kappaB activation in renal tubular epithelia and in interstitial cells that peaked 2-3 days after injury. To genetically antagonize tubular epithelial NF-kappaB activity, we generated mice expressing the human NF-kappaB super-repressor IkappaBalphaDeltaN in renal proximal, distal, and collecting duct epithelial cells. Compared with control mice, these mice exhibited improved renal function, reduced tubular apoptosis, and attenuated neutrophil and macrophage infiltration after IRI-induced AKI. Furthermore, tubular NF-kappaB-dependent gene expression profiles revealed temporally distinct functional gene clusters for apoptosis, chemotaxis, and morphogenesis. Primary proximal tubular cells isolated from IkappaBalphaDeltaN-expressing mice and exposed to hypoxia-mimetic agent cobalt chloride exhibited less apoptosis and expressed lower levels of chemokines than cells from control mice did. Our results indicate that postischemic NF-kappaB activation in renal tubular epithelia aggravates tubular injury and exacerbates a maladaptive inflammatory response.

Differentially Isotope-Labeled Nucleosomes To Study Asymmetric Histone Modification Crosstalk by Time-Resolved NMR Spectroscopy
Liokatis, S., Klingberg, R., Tan(*), S.; Schwarzer(*), D.
Angew Chem Int Ed Engl, 55:8262-8265
(2016)

Tags: In-Cell NMR (Selenko), Protein Chemistry (Schwarzer)

Abstract: Post-translational modifications (PTMs) of histones regulate chromatin structure and function. Because nucleosomes contain two copies each of the four core histones, the establishment of different PTMs on individual "sister" histones in the same nucleosomal context, that is, asymmetric histone PTMs, are difficult to analyze. Here, we generated differentially isotope-labeled nucleosomes to study asymmetric histone modification crosstalk by time-resolved NMR spectroscopy. Specifically, we present mechanistic insights into nucleosomal histone H3 modification reactions in cis and in trans, that is, within individual H3 copies or between them. We validated our approach by using the H3S10phK14ac crosstalk mechanism, which is mediated by the Gcn5 acetyltransferase. Moreover, phosphorylation assays on methylated substrates showed that, under certain conditions, Haspin kinase is able to produce nucleosomes decorated asymmetrically with two distinct types of PTMs.

Modulations of DNA Contacts by Linker Histones and Post-translational Modifications Determine the Mobility and Modifiability of Nucleosomal H3 Tails
Stützer(*), A., Liokatis, S., Kiesel(*), A., Schwarzer, D., Sprangers(*), R., Söding(*), J., Selenko, P.; Fischle(*), W.
Mol Cell, 61:247-259
(2016)

Tags: In-Cell NMR (Selenko), Protein Chemistry (Schwarzer)

Abstract: Post-translational histone modifications and linker histone incorporation regulate chromatin structure and genome activity. How these systems interface on a molecular level is unclear. Using biochemistry and NMR spectroscopy, we deduced mechanistic insights into the modification behavior of N-terminal histone H3 tails in different nucleosomal contexts. We find that linker histones generally inhibit modifications of different H3 sites and reduce H3 tail dynamics in nucleosomes. These effects are caused by modulations of electrostatic interactions of H3 tails with linker DNA and largely depend on the C-terminal domains of linker histones. In agreement, linker histone occupancy and H3 tail modifications segregate on a genome-wide level. Charge-modulating modifications such as phosphorylation and acetylation weaken transient H3 tail-linker DNA interactions, increase H3 tail dynamics, and, concomitantly, enhance general modifiability. We propose that alterations of H3 tail-linker DNA interactions by linker histones and charge-modulating modifications execute basal control mechanisms of chromatin function.

Substrate Hunting for the Myxobacterial CYP260A1 Revealed New 1alpha-Hydroxylated Products from C-19 Steroids
Khatri(*), Y., Ringle(*), M., Lisurek, M., von Kries, J. P., Zapp(*), J.; Bernhardt(*), R.
Chembiochem, 17:90-101
(2016)

Tags: Screening Unit (von Kries), Structural Bioinformatics and Protein Design (Krause, G.)

Abstract: Cytochromes P450 catalyze a variety of synthetically useful reactions. However, it is difficult to determine their physiological or artificial functions when a plethora of orphan P450 systems are present in a genome. CYP260A1 from Sorangium cellulosum So ce56 is a new member among the 21 available P450s in the strain. To identify putative substrates for CYP260A1 we used high-throughput screening of a compound library (ca. 17,000 ligands). Structural analogues of the type I hits were searched for biotechnologically relevant compounds, and this led us to select C-19 steroids as potential substrates. We identified efficient surrogate redox partners for CYP260A1, and an Escherichia coli-based whole-cell biocatalyst system was developed to convert testosterone, androstenedione, and their derivatives methyltestosterone and 11-oxoandrostenedione. A detailed (1) H and (13) C NMR characterization of the product(s) from C-19 steroids revealed that CYP260A1 is the very first 1alpha-steroid hydroxylase.

Lipopeptide-based micellar and liposomal carriers: Influence of surface charge and particle size on cellular uptake into blood brain barrier cells
Sydow, K., Nikolenko, H., Lorenz, D., Müller(*), R. H.; Dathe, M.
Eur J Pharm Biopharm, 109:130-139
(2016)

Tags: Peptide-Lipid-Interaction/ Peptide Transport (Dathe)

Abstract: Lipopeptide-based micelles and liposomes were found to differ in cell recognition and uptake mode into blood brain barrier (BBB) endothelial cells. Here we analyse the role of size and surface charge of micelles and liposomes composed of different lipopeptide sequences with respect to uptake into human brain capillary (HBMEC) and aortic (HAoEC) endothelial cells. Comparable to the dipalmitoylated apolipoprotein E-derived P2A2, lipopeptides of cationic poly-arginine (P2Rn), poly-lysine (P2Kn) and an anionic glutamic-acid sequence (P2En) self assemble into micelles (12-14nm in diameter) with high surface charge density, and bind to small (SUVs, about 24nm in diameter) and large (LUV, about 100nm in diameter) liposomes at variable lipid to peptide ratios. The interaction pattern of the resulting particles with endothelial cells is highly variable as revealed by confocal laser scanning microscopic (CLSM) and fluorescence assisted cell sorting (FACS) studies. Micelles and SUVs with high P2A2 density are efficiently and selectively internalized into HBMEC. P2Kn micelles strongly accumulate in both the cytosol and at the cell membrane, while the interaction of liposomes tagged with a low amount of P2A2 and P2Kn with the cells was reduced. Anionic micelles seem to dissociate in the presence of cells and P2En molecules incorporate into the cellular membrane whereas the negatively charged liposomes hardly interact with cells. Surprisingly, all poly-R-based particles show high selectivity for HBMEC compared to HAoEC, independent of particle size and peptide surface density. The P2Rn-mediated internalization is highly efficient and partially clathrin-dependent. The oligo-R lipopeptide is considered to be most promising to selectively transport different drug carriers into the blood brain barrier.

Structural disorder of monomeric alpha-synuclein persists in mammalian cells
Theillet, F. X., Binolfi, A., Bekei, B., Martorana(*), A., Rose, H. M., Stuiver, M., Verzini, S., Lorenz, D., van Rossum, M., Goldfarb(*), D.; Selenko, P.
Nature, 530:45-50
(2016)

Tags: In-Cell NMR (Selenko), Cellular Imaging (Wiesner)

Abstract: Intracellular aggregation of the human amyloid protein alpha-synuclein is causally linked to Parkinson's disease. While the isolated protein is intrinsically disordered, its native structure in mammalian cells is not known. Here we use nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy to derive atomic-resolution insights into the structure and dynamics of alpha-synuclein in different mammalian cell types. We show that the disordered nature of monomeric alpha-synuclein is stably preserved in non-neuronal and neuronal cells. Under physiological cell conditions, alpha-synuclein is amino-terminally acetylated and adopts conformations that are more compact than when in buffer, with residues of the aggregation-prone non-amyloid-beta component (NAC) region shielded from exposure to the cytoplasm, which presumably counteracts spontaneous aggregation. These results establish that different types of crowded intracellular environments do not inherently promote alpha-synuclein oligomerization and, more generally, that intrinsic structural disorder is sustainable in mammalian cells.

Dynamics of the Ligand Binding Domain Layer during AMPA Receptor Activation
Baranovic, J., Chebli, M., Salazar, H., Carbone, A. L., Faelber(*), K., Lau(*), A. Y., Daumke(*), O.; Plested, A. J.
Biophys J, 110:896-911
(2016)

Tags: Molecular Neuroscience and Biophysics (Plested)

Abstract: Ionotropic glutamate receptors are postsynaptic tetrameric ligand-gated channels whose activity mediates fast excitatory transmission. Glutamate binding to clamshell-shaped ligand binding domains (LBDs) triggers opening of the integral ion channel, but how the four LBDs orchestrate receptor activation is unknown. Here, we present a high-resolution x-ray crystal structure displaying two tetrameric LBD arrangements fully bound to glutamate. Using a series of engineered metal ion trapping mutants, we showed that the more compact of the two assemblies corresponds to an arrangement populated during activation of full-length receptors. State-dependent cross-linking of the mutants identified zinc bridges between the canonical active LBD dimers that formed when the tetramer was either fully or partially bound by glutamate. These bridges also stabilized the resting state, consistent with the recently published full-length apo structure. Our results provide insight into the activation mechanism of glutamate receptors and the complex conformational space that the LBD layer can sample.

Dynamic Nuclear Polarization Enhanced MAS NMR Spectroscopy for Structural Analysis of HIV-1 Protein Assemblies
Gupta(*), R., Lu(*), M., Hou(*), G., Caporini(*), M. A., Rosay(*), M., Maas(*), W., Struppe(*), J., Suiter(*), C., Ahn(*), J., Byeon(*), I. J., Franks, W. T., Orwick-Rydmark, M., Bertarello(*), A., Oschkinat, H., Lesage(*), A., Pintacuda(*), G., Gronenborn(*), A. M.; Polenova(*), T.
J Phys Chem B, 120:329-339
(2016)

Tags: NMR-Supported Structural Biology (Oschkinat)

Abstract: Mature infectious HIV-1 virions contain conical capsids composed of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20-64-fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar-based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4-18.8 T) and temperature (109-180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of the temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine side-chain conformers; unique intermolecular correlations across two CA molecules; and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR spectroscopy as an excellent tool for the characterization of HIV-1 assemblies.

High resolution observed in 800 MHz DNP spectra of extremely rigid type III secretion needles
Fricke, P., Mance(*), D., Chevelkov, V., Giller(*), K., Becker(*), S., Baldus(*), M.; Lange, A.
J Biomol NMR, 65:121-126
(2016)

Tags: Molecular Biophysics (Lange, A.)

Abstract: The cryogenic temperatures at which dynamic nuclear polarization (DNP) solid-state NMR experiments need to be carried out cause line-broadening, an effect that is especially detrimental for crowded protein spectra. By increasing the magnetic field strength from 600 to 800 MHz, the resolution of DNP spectra of type III secretion needles (T3SS) could be improved by 22 %, indicating that inhomogeneous broadening is not the dominant effect that limits the resolution of T3SS needles under DNP conditions. The outstanding spectral resolution of this system under DNP conditions can be attributed to its low overall flexibility.

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