Institute For Medizinische Physik Und Biophysik

Berlin, Germany

Institute For Medizinische Physik Und Biophysik

Berlin, Germany
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DeAzevedo E.R.,University of Sao Paulo | Ayrosa A.M.I.B.,University of Sao Paulo | Faria G.C.,University of Sao Paulo | Cervantes H.J.,University of Sao Paulo | And 4 more authors.
Magnetic Resonance in Chemistry | Year: 2010

This article describes a solid-state NMR (SSNMR) investigation of the influence of hydration and chemical cross-linking on the molecular dynamics of the constituents of the bovine pericardium (BP) tissues and its relation to the mechanical properties of the tissue. Samples of natural phenetylamine-diepoxide (DE)- and glutaraldehyde (GL)-fixed BP were investigated by 13C cross-polarization SSNMR to probe the dynamics of the collagen, and the results were correlated to the mechanical properties of the tissues, probed by dynamical mechanical analysis. For samples of natural BP, the NMR results show that the higher the hydration level the more pronounced the molecular dynamics of the collagen backbone and sidechains, decreasing the tissue's elastic modulus. In contrast, in DE- and GL-treated samples, the collagen molecules are more rigid, and the hydration seems to be less effective in increasing the collagenmolecular dynamics and reducing the mechanical strength of the samples. This is mostly attributed to the presence of cross-links between the collagen plates, which renders the collagen mobility less dependent on the water absorption in chemically treated samples. Copyright © 2010 John Wiley & Sons, Ltd.

Schwefel D.,Max Delbruck Centrum fur Molekulare Medizin | Schwefel D.,Free University of Berlin | Daumke O.,Max Delbruck Centrum fur Molekulare Medizin | Daumke O.,Institute For Medizinische Physik Und Biophysik
Small GTPases | Year: 2011

GTPases of Immunity-Associated Proteins (GIMAPs) are a family of guanine nucleotide binding (G) proteins which are implicated in the regulation of apoptosis in lymphocytes. GIMAPs are composed of an amino-terminal G domain and carboxy-terminal extensions of varying size. Our recent biochemical and structural analysis of a representative GIMAP family member, GIMAP2, revealed the molecular basis of GTPdependent oligomerization which involves two interfaces in the G domain. Whereas the amphipathic helix α7 in the C-terminal extension closely folds against the G domain in the GDP-bound state, it might be released in the GTPbound state to assemble interaction partners. We also showed that the GIMAP2 oligomer functions at the surface of lipid droplets in a Jurkat T cell line. Here, we review our recent work and discuss the GIMAP2 oligomer as a GTP-dependent protein scaffold at the surface of lipid droplets controlling apoptosis. © 2011 Landes Bioscience.

Kuhne J.,Ruhr University Bochum | Eisenhauer K.,Ruhr University Bochum | Ritter E.,Humboldt University of Berlin | Hegemann P.,Humboldt University of Berlin | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2015

Channelrhodopsins (ChRs) are light-gated ion channels that are widely used in optogenetics. They allow precise control of neuronal activity with light, but a detailed understanding of how the channel is gated and the ions are conducted is still lacking. The recent determination of the X-ray structural model in the closed state marks an important milestone. Herein the open state structure is presented and the early formation of the ion conducting pore is elucidated in atomic detail using time-resolved FTIR spectroscopy. Photo-isomerization of the retinal-chromophore causes a downward movement of the highly conserved E90, which opens the pore. Molecular dynamic (MD) simulations show that water molecules invade through this opened pore, Helix 2 tilts and the channel fully opens within ms. Since E90 is a highly conserved residue, the proposed E90-Helix2-tilt (EHT) model might describe a general activation mechanism and provides a new avenue for further mechanistic studies and engineering. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deuerling E.,University of Konstanz | Nikolay R.,University of Konstanz | Nikolay R.,Institute For Medizinische Physik Und Biophysik
BioSpektrum | Year: 2015

Ribosomes facilitate protein biosynthesis in all living cells. They consist of two subunits composed of protein and RNA constituents. Ribosome biogenesis is insufficiently explored due to its complexity and, at the same time, supposed to be an attractive target for new antimicrobials. For both scientific and pharmaceutical purposes the use of fluorescently labeled ribosomes (fluorosomes) could be a valuable tool. © 2015, Springer-Verlag Berlin Heidelberg.

Botev A.,Free University of Berlin | Munter L.-M.,Free University of Berlin | Wenzel R.,Free University of Berlin | Richter L.,Free University of Berlin | And 8 more authors.
Biochemistry | Year: 2011

The amyloid-β (Aβ) peptide is contained within the C-terminal fragment (β-CTF) of the amyloid precursor protein (APP) and is intimately linked to Alzheimer's disease. In vivo, Aβ is generated by sequential cleavage of β-CTF within the γ-secretase module. To investigate γ-secretase function, in vitro assays are in widespread use which require a recombinant β-CTF substrate expressed in bacteria and purified from inclusion bodies, termed C100. So far, little is known about the conformation of C100 under different conditions of purification and refolding. Since C100 dimerization influences the efficiency and specificity of γ-secretase cleavage, it is also of great interest to determine the secondary structure and the oligomeric state of the synthetic substrate as well as the binding properties of small molecules named γ-secretase modulators (GSMs) which we could previously show to modulate APP transmembrane sequence interactions [Richter et al. (2010) Proc. Natl. Acad. Sci. U.S.A. 107, 14597-14602]. Here, we use circular dichroism and continuouswave electron spin resonance measurements to show that C100 purified in a buffer containing SDS at micelleforming concentrations adopts a highly stable R-helical conformation, in which it shows little tendency to aggregate or to form higher oligomers than dimers. By surface plasmon resonance analysis and molecular modeling we show that the GSM sulindac sulfide binds to C100 and has a preference for C100 dimers. © 2010 American Chemical Society.

Munter L.M.,McGill University | Munter L.M.,Free University of Berlin | Sieg H.,Free University of Berlin | Bethge T.,Free University of Berlin | And 9 more authors.
Journal of the American Chemical Society | Year: 2013

The β-secretase or β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the enzyme responsible for the formation of amyloid-β peptides, which have a major role in Alzheimer pathogenesis. BACE1 has a transmembrane sequence (TMS), which makes it unique among related proteases. We noticed that the BACE1 TMS contains an uncommon sulfur-rich motif. The sequence MxxxCxxxMxxxCxMxC spans the entire TMS, resembles metal ion binding motifs, and is highly conserved among homologues. We used a synthetic 31-mer model peptide comprising the TMS to study metal ion binding and oligomerization. Applying diverse biochemical and biophysical techniques, we detected dimer and trimer formation of the TMS peptide with copper ions. Replacement of the central Cys466 by Ala essentially abolished these effects. We show that the peptide undergoes a redox reaction with copper ions resulting in a disulfide bridge involving Cys466. Further, we find peptide trimerization that depends on the presence of monovalent copper ions and the sulfhydryl group of Cys466. We identified Cys466 as a key residue for metal ion chelation and to be the core of an oligomerization motif of the BACE1-TMS peptide. Our results demonstrate a novel metal ion controlled oligomerization of the BACE1 TMS, which could have an enormous therapeutic importance against Alzheimer disease. © 2013 American Chemical Society.

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