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77 Publications visible to you, out of a total of 77
Inositol hexakisphosphate increases the size of platelet aggregates

Abstract (Expand)

The inositol phosphates, InsP5 and InsP6, have recently been identified as binding partners of fibrinogen, which is critically involved in hemostasis by crosslinking activated platelets at sites of … vascular injury. Here, we investigated the putative physiological role of this interaction and found that platelets increase their InsP6 concentration upon stimulation with the PLC-activating agonists thrombin, collagen I and ADP and present a fraction of it at the outer plasma membrane. Cone and plate analysis in whole blood revealed that InsP6 specifically increases platelet aggregate size. This effect is fibrinogen-dependent, since it is inhibited by an antibody that blocks fibrinogen binding to platelets. Furthermore, InsP6 has only an effect on aggregate size of washed platelets when fibrinogen is present, while it has no influence in presence of von Willebrand factor or collagen. By employing blind docking studies we predicted the binding site for InsP6 at the bundle between the γand βhelical subunit of fibrinogen. Since InsP6 is unable to directly activate platelets and it did not exhibit an effect on thrombin formation or fibrin structure, our data indicate that InsP6 might be a hemostatic agent that is produced by platelets upon stimulation with PLC-activating agonists to promote platelet aggregation by supporting crosslinking of fibrinogen and activated platelets.

Authors: Maria A. Brehm, Ulrike Klemm, Christoph Rehbach, Nina Erdmann, Katra Kolšek, Hongying Lin, Camilo Aponte-Santamaría, Frauke Gräter, Bernhard H. Rauch, Andrew M. Riley, Georg W. Mayr, Barry V.L. Potter, Sabine Windhorst

Date Published: 1st Mar 2019

Publication Type: Journal

How ARVC-Related Mutations Destabilize Desmoplakin: An MD Study

Abstract (Expand)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial heart disease linked to mutations in several desmosomal proteins, but the specific effects of these mutations on the molecular level … are poorly understood. Among the many documented ARVC-related genetic variants, a striking hotspot of nine mutations has been identified in the plakin domain of desmoplakin. This hotspot can be found at the meeting point of three different subdomains of desmoplakin: two spectrin repeats and a Src homology 3 domain. We set out to understand the effect of these mutations. We determine, using molecular dynamics simulations, how these mutations affect the mechanics of this interface, performing two different classes of simulations. First, we sample the dynamics of the plakin domain, in particular the tendency of the interdomain hinge to buckle, and then we apply an external force onto the constructs and determine the force necessary to break them. We find that surface-exposed mutations are not affecting the dynamics to a very large degree but that most buried mutations make the junction more flexible and decrease the rupture forces observed. Our data suggest that buried ARVC mutations destabilize desmoplakin and thereby impair desmosome integrity under tension.

Authors: Csaba Daday, Laura Marlene Mateyka, Frauke Gräter

Date Published: 1st Mar 2019

Publication Type: Journal

Structure and dynamics of the platelet integrin-binding C4 domain of von Willebrand factor

Abstract (Expand)

Von Willebrand factor (VWF) is a key player in the regulation of hemostasis by promoting recruitment of platelets to sites of vascular injury. An array of 6 C domains forms the dimeric C-terminal VWF … stem. Upon shear force activation, the stem adopts an open conformation allowing the adhesion of VWF to platelets and the vessel wall. To understand the underlying molecular mechanism and associated functional perturbations in disease-related variants, knowledge of high-resolution structures and dynamics of C domains is of paramount interest. Here, we present the solution structure of the VWF C4 domain, which binds to the platelet integrin and is therefore crucial for the VWF function. In the structure, we observed 5 intra- and inter-subdomain disulfide bridges, of which 1 is unique in the C4 domain. The structure further revealed an unusually hinged 2-subdomain arrangement. The hinge is confined to a very short segment around V2547 connecting the 2 subdomains. Together with 2 nearby inter-subdomain disulfide bridges, this hinge induces slow conformational changes and positional alternations of both subdomains with respect to each other. Furthermore, the structure demonstrates that a clinical gain-of-function VWF variant (Y2561) is more likely to have an effect on the arrangement of the C4 domain with neighboring domains rather than impairing platelet integrin binding.

Authors: Emma-Ruoqi Xu, Sören von Bülow, Po-Chia Chen, Peter J. Lenting, Katra Kolšek, Camilo Aponte-Santamaría, Bernd Simon, Jaelle Foot, Tobias Obser, Reinhard Schneppenheim, Frauke Gräter, Cécile V. Denis, Matthias Wilmanns, Janosch Hennig

Date Published: 24th Jan 2019

Publication Type: Journal

Studying Functional Disulphide Bonds by Computer Simulations

Abstract (Expand)

Biochemical and structural data reveal important aspects of the properties and function of a protein disulphide bond. Molecular dynamics simulations can complement this experimental data and can yield … valuable insights into the dynamical behavior of the disulphide bond within the protein environment. Due to the increasing accuracy of the underlying energetic description and the increasing computational power at hand, such simulations have now reached a level, at which they can also make quantitative and experimentally testable predictions. We here give an overview of the computational methods used to predict functional aspects of protein disulphides, including the prestress, protein allosteric effects upon thiol/disulphide exchange, and disulphide redox potentials. We then outline in detail the use of free-energy perturbation methods to calculate the redox potential of a protein disulphide bond of interest. In a step-by-step protocol, we describe the workflow within the MD suite Gromacs, including practical advice on the simulation setup and choice of parameters. For other disulphide-related simulation methods, we refer to resources available online.

Authors: Frauke Gräter, Wenjin Li

Date Published: 2019

Publication Type: InBook

Protein S-Bacillithiolation Functions in Thiol Protection and Redox Regulation of the Glyceraldehyde-3-Phosphate Dehydrogenase Gap in Staphylococcus aureus Under Hypochlorite Stress.

Abstract (Expand)

AIMS: Bacillithiol (BSH) is the major low-molecular-weight thiol of the human pathogen Staphylococcus aureus. In this study, we used OxICAT and Voronoi redox treemaps to quantify hypochlorite-sensitive … protein thiols in S. aureus USA300 and analyzed the role of BSH in protein S-bacillithiolation. RESULTS: The OxICAT analyses enabled the quantification of 228 Cys residues in the redox proteome of S. aureus USA300. Hypochlorite stress resulted in >10% increased oxidation of 58 Cys residues (25.4%) in the thiol redox proteome. Among the highly oxidized sodium hypochlorite (NaOCl)-sensitive proteins are five S-bacillithiolated proteins (Gap, AldA, GuaB, RpmJ, and PpaC). The glyceraldehyde-3-phosphate (G3P) dehydrogenase Gap represents the most abundant S-bacillithiolated protein contributing 4% to the total Cys proteome. The active site Cys151 of Gap was very sensitive to overoxidation and irreversible inactivation by hydrogen peroxide (H2O2) or NaOCl in vitro. Treatment with H2O2 or NaOCl in the presence of BSH resulted in reversible Gap inactivation due to S-bacillithiolation, which could be regenerated by the bacilliredoxin Brx (SAUSA300_1321) in vitro. Molecular docking was used to model the S-bacillithiolated Gap active site, suggesting that formation of the BSH mixed disulfide does not require major structural changes. Conclusion and Innovation: Using OxICAT analyses, we identified 58 novel NaOCl-sensitive proteins in the pathogen S. aureus that could play protective roles against the host immune defense and include the glycolytic Gap as major target for S-bacillithiolation. S-bacillithiolation of Gap did not require structural changes, but efficiently functions in redox regulation and protection of the active site against irreversible overoxidation in S. aureus. Antioxid. Redox Signal. 28, 410-430.

Authors: Marcel Imber, Nguyen Thi Thu Huyen, Agnieszka J. Pietrzyk-Brzezinska, Vu Van Loi, Melanie Hillion, Jörg Bernhardt, Lena Thärichen, Katra Kolšek, Malek Saleh, Chris J. Hamilton, Lorenz Adrian, Frauke Gräter, Markus C. Wahl, Haike Antelmann

Date Published: 20th Feb 2018

Publication Type: Journal

Autoregulation of von Willebrand factor function by a disulfide bond switch

Abstract

Not specified

Authors: Diego Butera, Freda Passam, Lining Ju, Kristina M. Cook, Heng Woon, Camilo Aponte-Santamaría, Elizabeth Gardiner, Amanda K. Davis, Deirdre A. Murphy, Agnieszka Bronowska, Brenda M. Luken, Carsten Baldauf, Shaun Jackson, Robert Andrews, Frauke Gräter, Philip J. Hogg

Date Published: 2018

Publication Type: Journal

Stability of Biological Membranes upon Mechanical Indentation

Abstract

Not specified

Authors: Florian Franz, Camilo Aponte-Santamaría, Csaba Daday, Vedran Miletić, Frauke Gräter

Date Published: 2018

Publication Type: Journal

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