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77 Publications visible to you, out of a total of 77
DOPA Residues Endow Collagen with Radical Scavenging Capacity

Abstract (Expand)

Here we uncover collagen, the main structural protein of all connective tissues, as a redox-active material. We identify dihydroxyphenylalanine (DOPA) residues, post-translational oxidation products … of tyrosine residues, to be common in collagen derived from different connective tissues. We observe that these DOPA residues endow collagen with substantial radical scavenging capacity. When reducing radicals, DOPA residues work as redox relay: they convert to the quinone and generate hydrogen peroxide. In this dual function, DOPA outcompetes its amino acid precursors and ascorbic acid. Our results establish DOPA residues as redox-active side chains of collagens, probably protecting connective tissues against radicals formed under mechanical stress and/or inflammation.

Authors: Markus Kurth, Uladzimir Barayeu, Hassan Gharibi, Andrei Kuzhelev, Kai Riedmiller, Jennifer Zilke, Kasimir Noack, Vasyl Denysenkov, Reinhard Kappl, Thomas F. Prisner, Roman A. Zubarev, Tobias P. Dick, Frauke Gräter

Date Published: 3rd Apr 2023

Publication Type: Journal

Energetics and kinetics of membrane permeation of photoresists for bioprinting

Abstract

Not specified

Authors: Lucas Diedrich, Matthias Brosz, Tobias Abele, Salome Steinke, Frauke Gräter, Kerstin Göpfrich, Camilo Aponte-Santamaría

Date Published: 28th Mar 2023

Publication Type: Journal

FERM domains recruit ample PI(4,5)P2s to form extensive protein-membrane attachments

Abstract (Expand)

The four-point-one ezrin-radixin-moesin homology (FERM) protein domain is a multifunctional protein-lipid binding site, constituting an integral part of numerous membrane-associated proteins. Its … interaction with the lipid phosphatidylinositol-4,5-bisphosphate (PIP2), located at the inner leaflet of eukaryotic plasma membranes, is important for localization, anchorage, and activation of FERM-containing proteins. FERM-PIP2 complexes structurally determined so far exclusively feature a 1:1 binding stoichiometry of protein and lipid, with a few basic FERM residues neutralizing the −4 charge of the bound PIP2. Whether this picture from static crystal structures also applies to the dynamic interaction of FERM domains on PIP2 membranes is unknown. We here quantified the stoichiometry of FERM-PIP2 binding in a lipid bilayer using atomistic molecular dynamics simulations and experiments on solid supported membranes for the FERM domains of focal adhesion kinase and ezrin. In contrast to the structural data, we find much higher average stoichiometries of FERM-PIP2 binding, amounting to 1:3 or 1:4 ratios, respectively. In simulations, the full set of basic residues at the membrane interface, 7 and 15 residues for focal adhesion kinase and ezrin, respectively, engages in PIP2 interactions. In addition, Na ions enter the FERM-membrane binding interface, compensating negative PIP2 charges in case of high charge surpluses from bound PIP2. We propose the multivalent binding of FERM domains to PIP2 in lipid bilayers to significantly enhance the stability of FERM-membrane binding and to render the FERM-membrane linkage highly adjustable.

Authors: Thomas Ehret, Tim Heißenberg, Svenja de Buhr, Camilo Aponte-Santamaría, Claudia Steinem, Frauke Gräter

Date Published: 21st Feb 2023

Publication Type: Journal

Intrinsically disordered region of talin’s FERM domain functions as an initial PIP2 recognition site

Abstract (Expand)

Focal adhesions (FAs) mediate the interaction of the cytoskeleton with the extracellular matrix in a highly dynamic fashion. Talin is a central regulator, adaptor protein, and mechano-sensor of FA … complexes. For recruitment and firm attachment at FAs, talin’s N-terminal FERM domain binds to phosphatidylinositol 4,5-bisphosphate (PIP2)-enriched membranes. A newly published autoinhibitory structure of talin-1, where the known PIP2 interaction sites are covered up, lead us to hypothesize that a hitherto less examined loop insertion of the FERM domain acts as an additional and initial site of contact. We evaluated direct interactions of talin-1 with a PIP2 membrane by means of atomistic molecular dynamics simulations. We show that this unstructured, 33-residue-long loop strongly interacts with PIP2 and can facilitate further membrane contacts, including the canonical PIP2 interactions, by serving as a flexible membrane anchor. Under force as present at FAs, the extensible FERM loop ensures talin maintains membrane contacts when pulled away from the membrane by up to 7 nm. We identify key basic residues of the anchor mediating the highly dynamic talin-membrane interaction. Our results put forward an intrinsically disordered loop as a key and highly adaptable PIP2 recognition site of talin and potentially other PIP2-binding mechano-proteins.

Authors: Jannik Buhr, Florian Franz, Frauke Gräter

Date Published: 21st Feb 2023

Publication Type: Journal

Bond dissociation energies of X–H bonds in proteins

Abstract (Expand)

Knowledge of reliable X−H bond dissociation energies (X = C, N, O, S) for amino acids in proteins is key for studying the radical chemistry of proteins. X−H bond dissociation energies of model dipeptides … were computed using the isodesmic reaction method at the BMK/6-31+G(2df,p) and G4(MP2)-6X levels of theory. The density functional theory values agree well with the composite- level calculations. By this high level of theory, combined with a careful choice of reference compounds and peptide model systems, our work provides a highly valuable data set of bond dissociation energies with unprecedented accuracy and comprehensiveness. It will likely prove useful to predict protein biochemistry involving radicals, e.g., by machine learning.

Authors: Authors Wojtek Treyde, Kai Riedmiller, Frauke Gräter

Date Published: 1st Dec 2022

Publication Type: Journal

Structure and dynamics of the von Willebrand Factor C6 domain

Abstract (Expand)

Von Willebrand disease (VWD) is a bleeding disorder with different levels of severity. VWD-associated mutations are located in the von Willebrand factor (VWF) gene, coding for the large multidomain … plasma protein VWF with essential roles in hemostasis and thrombosis. On the one hand, a variety of mutations in the C-domains of VWF are associated with increased bleeding upon vascular injury. On the other hand, VWF gain-of-function (GOF) mutations in the C4 domain have recently been identified, which induce an increased risk of myocardial infarction. Mechanistic insights into how these mutations affect the molecular behavior of VWF are scarce and holistic approaches are challenging due to the multidomain and multimeric character of this large protein. Here, we determine the structure and dynamics of the C6 domain and the single nucleotide polymorphism (SNP) variant G2705R in C6 by combining nuclear magnetic resonance spectroscopy, molecular dynamics simulations and aggregometry. Our findings indicate that this mutation mostly destabilizes VWF by leading to a more pronounced hinging between both subdomains of C6. Hemostatic parameters of variant G2705R are close to normal under static conditions, but the missense mutation results in a gain-of-function under flow conditions, due to decreased VWF stem stability. Together with the fact that two C4 variants also exhibit GOF characteristics, our data underline the importance of the VWF stem region in VWF’s hemostatic activity and the risk of mutation-associated prothrombotic properties in VWF C-domain variants due to altered stem dynamics.

Authors: Po-Chia Chen, Fabian Kutzki, Angelika Mojzisch, Bernd Simon, Emma-Ruoqi Xu, Camilo Aponte-Santamaría, Kai Horny, Cy Jeffries, Reinhard Schneppenheim, Matthias Wilmanns, Maria A. Brehm, Frauke Gräter, Janosch Hennig

Date Published: 18th Nov 2022

Publication Type: Journal

Hydropersulfides inhibit lipid peroxidation and ferroptosis by scavenging radicals

Abstract (Expand)

erroptosis is a type of cell death caused by radical-driven lipid peroxidation, leading to membrane damage and rupture. Here we show that enzymatically produced sulfane sulfur (S0) species, specifically … hydropersulfides, scavenge endogenously generated free radicals and, thereby, suppress lipid peroxidation and ferroptosis. By providing sulfur for S0 biosynthesis, cysteine can support ferroptosis resistance independently of the canonical GPX4 pathway. Our results further suggest that hydropersulfides terminate radical chain reactions through the formation and self-recombination of perthiyl radicals. The autocatalytic regeneration of hydropersulfides may explain why low micromolar concentrations of persulfides suffice to produce potent cytoprotective effects on a background of millimolar concentrations of glutathione. We propose that increased S0 biosynthesis is an adaptive cellular response to radical-driven lipid peroxidation, potentially representing a primordial radical protection system.

Authors: Uladzimir Barayeu, Danny Schilling, Mohammad Eid, Thamara Nishida Xavier da Silva, Lisa Schlicker, Nikolina Mitreska, Christopher Zapp, Frauke Gräter, Aubry K. Miller, Reinhard Kappl, Almut Schulze, José Pedro Friedmann Angeli, Tobias P. Dick

Date Published: 15th Sep 2022

Publication Type: Journal

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