Biology subjects

Graeter, F.

Publications and source records attributed to Graeter, F..

11 recordsLinked to original sources

bioRxiv2026

The phosphoproteomic landscape of the DNA damage response

The DNA damage response (DDR) comprises an intricate network of protein-protein interactions and signaling pathways activated by DNA lesions and genomic instability. Central to this response is protein phosphorylation, which orchestrates DNA repair, cell cycle checkpoint activation, and chromatin organization. The response of the human phosphoproteome to different DNA damage-inducing agents and the functional role of regulated phosphorylation sites remains insufficiently characterized. Here, we systematically profiled the cellular phosphoproteome following exposure to eleven DNA damage-inducing agents that humans encounter physiologically or during cancer therapy. We identified a core set of DNA damage responsive phosphorylation sites, along with DDR signatures associated with DNA double strand breaks, replication stress and a pleiotropic response. Regulated phosphorylation sites are enriched within intrinsically disordered regions (IDRs), often forming clusters of nearby modifications that can affect IDR conformations or overlap with short linear interaction motifs. We discover that the RNA damage response predominantly shapes the changes induced by reactive aldehyde formaldehyde, alkylating agent methyl methanesulfonate and oxidative stress. Finally, we demonstrate that the proteasome-associated ubiquitin E3 ligase UBE3A is targeted by ATM and ATR kinases, thus linking proteasome regulation with the DDR.

cell biology↗

bioRxiv2026

Introducing non-enzymatic crosslinks into atomistic simulations of collagen fibrils

MotivationCollagen fibrils are the primary load-bearing units of connective tissues. However, generating atomistic, simulation-ready models remains challenging due to collagens hierarchical organization and the diversity of its crosslinking network across tissues, ages, and metabolic states. Notably, non-enzymatic advanced glycation end-product (AGE) crosslinks--central to aging and diabetic complications--are largely absent from current atomistic fibril modelling workflows. ResultsHere, we present an extension of the ColBuilder framework to generate atomistic collagen fibril models that incorporate three representative AGE-derived crosslinks (glucosepane, pentosidine, and MOLD) alongside enzymatic crosslinks. Amber99-compatible parameters are provided and assessed against QM-optimized reference geometries using all-atom molecular dynamics (MD) simulations. As proof-of-concept, we examine the mechanical response of single D-period collagen microfibrils featuring enzymatic-only, AGE-only, and mixed crosslink patterns in Molecular Dynamics simulations under force, and observe that AGE crosslinks differently impact the fibril structure compared to enzymatic crosslinks. The extension to ColBuilder can aid future structure-based research on collagen aging. Availability and implementationColBuilder is available as an open-source Python command-line package at https://github.com/graeter-group/colbuilder.

bioinformatics↗

bioRxiv2025

Coarse-grained Martini 3 model of chondroitin sulfate A

Chondroitin sulfate A (CSA) is a negatively charged linear glycosaminoglycan which plays a vital role in many biological processes. Research on CSA has been challenging due to its size, chemical heterogeneity, and multitude of binding partners. To address these issues, we developed a model of CSA for coarse-grained molecular dynamics simulations based on the Martini 3 force-field. We demonstrate that this model is capable of reproducing atomistic properties of the repeating CSA disaccharide unit, including its molecular volume and bonded interactions, and structural polymer properties of CSA chains of different lengths. In particular, for biologically-relevant long chains and despite of using an explicit solvent, the computational cost is significantly reduced, relative to the cost equivalent atomistic simulations would require. The compatibility of the model with the Martini G[o] protein model was tested by retrieving the forceresponse of the CSA-malaria adhesin VAR2CSA complex. Importantly, we explored the influence of electrostatics on CSA aggregation. We show that the default Martini 3 parameters lead to over-aggregation. We provide at least three different strategies to alleviate this issue, making use of a bigger bead for sodium cations, reflecting its hydration shell, partial ionic charges, as a mean-field resource to take into account electronic polarizability, and, optionally, particle-mesh Ewald summation as a more robust treatment of long-range electrostatics. Our model opens the door for predictive modeling of CSA and potentially other chondroitin sulfates. In addition, this model provides insights for the further development of coarse-grained models of highly-charged systems.

biophysics↗

bioRxiv2025

KIMMDY: a biomolecular reaction emulator

Molecular simulations have become indispensable in biological research. Their accuracy continues to improve, but directly modelling biochemical reactions - central to all life processes - remains computationally challenging. Here, we present a biomolecular reaction emulator that models reactions across conformational ensembles using kinetic Monte Carlo. Our method, KIMMDY, is capable of handling dynamic, large-scale systems with successive, competing reactions, even on the second timescale or slower. It leverages graph neural networks for large-scale prediction of reaction rates, while also being capable of using simpler physics-based or heuristic models. We validate our approach against experimental data and showcase its power and versatility through a series of applications, including radical reactions, nucleophilic substitutions, and photodimerization. Example systems span proteins and DNA. KIMMDY aids the understanding of biochemical reaction cascades in complex systems, helps to re-interpret experimental data, and can inspire future wet-lab experiments.

biochemistry↗

bioRxiv2023

O-glycans Expand Lubricin and Attenuate its Viscosity and Shear Thinning

Lubricin, an intrinsically disordered glycoprotein, plays a pivotal role in facilitating smooth movement and ensuring the enduring functionality of synovial joints. The central domain of this protein serves as a source of this excellent lubrication, and is characterized by its highly glycosylated, negatively charged, and disordered structure. However, the influence of O-glycans on the viscosity of lubricin remains unclear. In this study, we employ molecular dynamics simulations in absence and presence of shear, along with continuum simulations, to elucidate the intricate interplay between O-glycans and lubricin and the impact of O-glycans on lubricins conformational properties and viscosity. We find the presence of O-glycans to induce a more extended conformation in fragments of the disordered region of lubricin. These O-glycans contribute to a reduction in solution viscosity but at the same time weaken shear thinning at high shear rates, compared to non-glycosylated systems with the same density. This effect is attributed to the steric and electrostatic repulsion between the fragments, which prevent their conglomeration and structuring. Our computational study yields a mechanistic mechanism underlying previous experimental observations of lubricin and paves the way to more rationally understanding its function in the synovial fluid.

biophysics↗

bioRxiv2023

Insights into human outer kinetochore assembly and force transmission from a structure-function analysis of the KMN network

The biorientation of chromosomes during cell division is necessary for precise dispatching of a mother cells chromosomes into its two daughters. Kinetochores, large layered structures built on specialized chromosome loci named centromeres, promote biorientation by binding and sensing spindle microtubules. The kinetochore outer layer consists of a 10-subunit apparatus comprising Knl1C, Mis12C, and Ndc80C subcomplexes (KMN network). The KMN network is highly elongated and docks on kinetochores and microtubules using interfaces at its opposite extremes. Here, we combine cryo-EM reconstructions and AlphaFold2 predictions to generate a model of the KMN network that reveals all intra-KMN interfaces. We identify and functionally validate two interaction interfaces that link Mis12C to Ndc80C and Knl1C. Through targeted interference experiments and molecular dynamics simulations we demonstrate this mutual organization stabilizes the KMN network. Our work reports the first comprehensive structural and functional analysis of the microtubule binding machinery of kinetochores and elucidates a path of microtubule-generated force transmission

molecular biology↗

bioRxiv2023

DOPA residues endow collagen with radical scavenging capacity

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.

biophysics↗

bioRxiv2022

Myristoyl's dual role in allosterically regulating and localizing Abl kinase

c-Abl kinase, a key signalling hub in many biological processes ranging from cell development to proliferation, is tightly regulated by two inhibitory Src homology domains. An N-terminal myristoyl-modification can bind to a hydrophobic pocket in the kinase C-lobe, which stabilizes the auto-inhibitory assembly. Activation is triggered by myristoyl release. We used molecular dynamics simulations to show how both myristoyl and the Src homology domains are required to impose the full inhibitory effect on the kinase domain, and reveal the allosteric transmission pathway at residue-level resolution. Importantly, we find myristoyl insertion into a membrane to thermodynamically compete with binding to c-Abl. Myristoyl thus not only localizes the protein to the cellular membrane, but membrane attachment at the same time enhances activation of c-Abl by stabilizing its pre-activated state. Our data put forward a model in which lipidation tightly couples kinase localization and regulation, a scheme that currently appears to be unique for this non-receptor tyrosine kinase.

biophysics↗

bioRxiv2022

The role of hydrodynamic flow in the self-assembly of dragline spider silk proteins

Hydrodynamic flow in the spider duct induces conformational changes in dragline spider silk proteins (spidroins) and drives their assembly, but the underlying physical mechanisms are still elusive. Here we address this challenging multiscale problem with a complementary strategy of atomistic and coarse-grained Molecular Dynamics (MD) simulations with uniform flow. The conformational changes at the molecular level were analyzed for single tethered spider silk peptides. Uniform flow leads to coiled-to-stretch transitions and pushes alanine residues into {beta}-sheet and Poly-Proline II (PPII) conformations. Coarse-grained simulations of the assembly process of multiple semi-flexible block copolymers using multi-particle collision dynamics reveal that the spidroins aggregate faster but into low-order assemblies when they are less extended. At medium-to-large peptide extensions (50%-80%), assembly slows down and becomes reversible with frequent association and dissociation events, while spidroin alignment increases and alanine repeats form ordered regions. Our work highlights the role of flow in guiding silk self-assembly into tough fibers by enhancing alignment and kinetic reversibility, a mechanism likely relevant for other proteins whose function depends on hydrodynamic flow.

biophysics↗

bioRxiv2022

Dynamic Disulfide Bond Topologies in von-Willebrand-Factor's C4-Domain Undermine Platelet Binding

BackgroundThe von Willebrand Factor (vWF) is a key player in regulating hemostasis through adhesion of platelets to sites of vascular injury. It is a large multi-domain mechano-sensitive protein stabilized by a net of disulfide bridges. Binding to platelet integrin is achieved by the vWF-C4 domain which exhibits a fixed fold, even under conditions of severe mechanical stress, but only if critical internal disulfide bonds are closed. ObjectiveTo quantitatively determine C4s disulfide topologies and their implication in vWFs platelet-binding function via integrin. MethodsWe employed a combination of classical Molecular Dynamics and quantum mechanical simulations, mass spectrometry, site-directed mutagenesis, and platelet binding assays. ResultsWe quantitatively show that two disulfide bonds in the vWF-C4 domain, namely the two major force-bearing ones, are partially reduced in human blood. Reduction leads to pronounced conformational changes within C4 that considerably affect the accessibility of the RGD-integrin binding motif, and thereby impair integrin-mediated platelet binding. Our combined approach also reveals that reduced species in the C4 domain undergo specific thiol/disulfide exchanges with the remaining disulfide bridges, in a process in which mechanical force may increase the proximity of specific reactant cysteines, further trapping C4 in a state of low integrin-binding propensity. We identify a multitude of redox states in all six vWF-C domains, suggesting disulfide bond reduction and swapping to be a general theme. ConclusionOverall, our data put forward a mechanism in which disulfide bonds dynamically swap cysteine partners and control the interaction of vWF with integrin and potentially other partners, thereby critically influencing its hemostatic function. EssentialsO_LIPlatelet integrins interact with the disulfide-bonded C4 domain of von Willebrand Factor C_LIO_LIThe redox state of vWF-C4s disulfide bonds is studied by molecular simulations and experiments C_LIO_LITwo bonds are reduced causing C4 unfolding and disulfide swapping C_LIO_LIOpening of disulfide bonds impairs integrin-mediated platelet binding C_LI

biophysics↗

bioRxiv2021

ATP allosterically stabilizes Integrin-linked kinase for efficient force generation

Focal adhesions link the actomyosin cytoskeleton to the extracellular matrix regulating cell adhesion, shape, and migration. Adhesions are dynamically assembled and disassembled in response to extrinsic and intrinsic forces, but how the essential adhesion component intergrin-linked kinase (ILK) dynamically responds to mechanical force and what role ATP bound to this pseudokinase plays remains elusive. Here, we apply force-probe molecular dynamics simulations of human ILK:-parvin coupled to traction force microscopy to explore ILK mechanotransducing functions. We identify two key saltbridge-forming arginines within the allosteric, ATP-dependent force-propagation network of ILK. Disrupting this network by mutation impedes parvin binding, focal adhesion stabilization, force generation, and thus migration. Under tension, ATP shifts the balance from rupture of the complex to protein unfolding, indicating that ATP increases the force threshold required for focal adhesion disassembly. Our study proposes a new role of ATP as an obligatory binding partner for structural and mechanical integrity of the pseudokinase ILK, ensuring efficient cellular force generation and migration.

biophysics↗