Biology subjects

Arya, G.

Publications and source records attributed to Arya, G..

At least 19 recordsLinked to original sources

bioRxiv2026

Engineered nanosponges mitigate peripheral stress-induced neuroinflammation and restore cognitive function

Systemic inflammation is increasingly recognized as a key driver of neuroinflammation and cognitive dysfunction, particularly in the aging population. Yet, therapeutic interventions that broadly attenuate circulating inflammatory mediators without suppressing host immunity remain limited. Here, we report the development of taurine functionalized hyaluronic acid nanosponges (HA Tau) that blunt systemic inflammatory cascades to protect against downstream neurocognitive impairment. Using molecular docking calculations and experimental validations, we show that taurine functionalization enhances multivalent interactions with diverse cytokines, enabling broad-spectrum sequestration of inflammatory proteins from both murine and human plasma while preserving the intrinsic hypochlorous acid neutralizing ability of taurine. In aged mice undergoing orthopedic surgery, systemic administration of HA Tau nanosponges lowered the levels of circulating inflammatory mediators, preserved blood brain barrier integrity, and attenuated glial cell activation. These effects were accompanied by improved hippocampal neuronal activity and spatial working memory in mice. By dampening peripheral inflammatory surges, the nanosponges limit peripheral-to-central inflammatory signaling without directly targeting the central nervous system. Collectively, these findings demonstrate systemic inflammatory modulation could be an effective strategy for mitigating peripheral insult-induced neuroinflammation and cognitive decline, and position HA Tau nanosponges as a versatile biomaterial platform for treating inflammation-driven disorders.

bioengineering↗

bioRxiv2026

Martini 3 Coarse-Grained Model of DNA for Heterogeneous Molecular Systems

DNA often functions in heterogeneous molecular systems containing proteins, lipids, polymers, and other materials. All-atom molecular dynamics simulations can be used to study DNA in these multicomponent systems, but computational cost limits the accessible system sizes and time scales. Coarse-grained models extend these scales, but existing DNA models are generally not designed for interactions with a broad range of other molecular species. To fill this gap, we develop a coarse-grained model of DNA designed for use with the Martini 3 force field. The model was parameterized through an iterative Bayesian optimization workflow, which used a scaled Wasserstein metric to compare distributions of local geometrical features and global structure from coarse-grained simulations against all-atom reference simulations. The optimized model captures key structural and mechanical properties of single- and double-stranded DNA across varying strand lengths and ionic conditions, while retaining compatibility with the broader Martini 3 ecosystem. This compatibility enables DNA to be integrated with a broad range of molecular systems, as we illustrate through simulations of double-stranded DNA bound to a transcription factor, cholesterol-tagged DNA duplex interacting with a lipid bilayer, a crossover-containing DNA nanostructure, and single-stranded DNA adsorbing onto graphene. Together, these results establish a transferable coarse-grained model of DNA for simulations of heterogeneous biomolecular and engineered systems.

biophysics↗

bioRxiv2025

Enterococcus faecium sagA mutants have cell envelope defects influencing antibiotic resistance and bacteriophage susceptibility

Enterococcus faecium is a Gram-positive bacterium that is resident to the intestines of animals including humans. E. faecium is also an opportunistic pathogen that causes multidrug resistant (MDR) infections. Bacteriophages (phages) have been proposed as therapeutics for the treatment of MDR infections, however, an obstacle for phage therapy is the emergence of phage resistance. Despite this, the development of phage resistance can impact bacterial fitness, thus, understanding the molecular basis of fitness costs associated with phage resistance can likely be leveraged as an antimicrobial strategy. We discovered that phage resistant E. faecium harbor mutations in the cell wall hydrolase gene sagA. SagA cleaves crosslinked peptidoglycan (PG) involved in PG remodeling. We show that mutations in sagA compromise E. faecium PG hydrolysis rendering them sensitive to {beta}-lactam antibiotics. sagA mutants have cell envelope integrity defects, increased cellular permeability, and aberrant distribution of penicillin binding proteins. This corresponds to a growth defect where cells have abnormal division septa, membrane blebbing, and the formation of mini cells. The dysregulation of the cell envelope in sagA mutants alters the binding of phages to the E. faecium cell surface. Our data support a model where phage infection of E. faecium requires phages to localize to sites of peptidoglycan remodeling at the cell poles and division septa. Our findings show that by altering the function of a single PG hydrolase, E. faecium loses intrinsic {beta}-lactam resistance. This indicates that phage therapy could help revive certain antibiotics when used in combination.

microbiology↗

bioRxiv2025

Malaria parasite population genomics during an elimination program in Eastern Myanmar

BackgroundWe investigated parasite population genomics during an intensive malaria elimination program in Kayin State (Myanmar), in which malaria posts were used for rapid detection and treatment of malaria cases, while mass drug administration (MDA) was used in villages with high submicroscopic reservoirs. MethodsWe collected 5014 dried blood spots from Plasmodium falciparum infected patients from 413 malaria posts, over 58-months (November 2015 - August 2020), and sequenced 2270 parasite genomes, each with geographic references (latitude and longitude). We used identity-by-descent (IBD) relationships to examine how control efforts impact parasite population structure. FindingsParasites were genetically depauperate: 1726 single-genotype infections comprised 166 unique genomes ([≥]90% IBD), while nine families ([≥]45% IBD) accounted for 62{middle dot}5% of parasites sampled. We observed localized, temporally stable transmission of unique parasite genotypes, identifying transmission chains. Parasite relatedness was positively correlated up to approximately 20 km revealing the scale of parasite subpopulations. Kelch13 diversity was stable from 2016-2019, but only one predominant clonal genotype (kelch13-R561H) remained in 2020. MDA resulted in parasite founder effects, providing genomic evidence for the efficacy of this malaria control tool. InterpretationOur genomic data show that parasite population size decreased over the study period, and we observed regional distribution of parasite genotypes, which can define operational units for parasite control. One parasite genotype (kelch13-R561H) from the north rose to high frequency in 2020, because transmission was halted elsewhere in the control area. Future surveillance will reveal whether this genotype spreads to neighboring regions. Genetic drift may have a stronger impact on parasite population structure than selection in low-transmission elimination settings. FundingNational Institutes of Health; Wellcome Trust; Global Fund to Fight against AIDS, Tuberculosis and Malaria; The Bill and Melinda Gates Foundation. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSThis study describes the genomic analysis of malaria parasites collected during a malaria elimination program targeting four townships (Myawaddy, Kawkareik, Hlaingbwe, and Hpapun) in Kayin State, eastern Myanmar. We searched PubMed on May 10, 2025, using the terms: "malaria", "transmission", "drug resistance", "southeast Asia" and "genetic surveillance" without any date or language restrictions. Our search yielded 58 publications, including reports on declined immunity to malaria and increased drug resistance in southeast Asia; genetic diversity and population structure shaped by mass drug administration, transmission intensity, human movement and mosquito ecology; and the spread of kelch13 and pfcrt mutations conferring dihydroartemimsinin-piperaquine resistance in east southeast Asia countries. Added value of this studyWe sequenced and analyzed 2270 Plasmodium falciparum whole genomes (each with geographic location) collected between November 2015 and August 2020 in Kayin State. We described fine-scale molecular epidemiology changes during intense malaria elimination interventions. We observed localized, temporally stable transmission of parasite genotypes, with different parasite families and kelch13 haplotypes predominating in different subregions over the 5-year period. We found kelch13 haplotypes with local or regional origin, but none originating from eastern southeast Asia. The genomic data indicated decreasing parasite population size, but we observed no selection towards drug-resistance parasites. In 2020, only one predominant lineage (kelch13-R561H) remained in our studying region, consistent with genetic drift in a pre-elimination setting. Implications of all the available evidenceThe parasite population was genetically depauperate, with a spatially localized and temporally stable distribution of parasite lineages, and declining population size. In this situation genetic drift may play a heightened role in parasite epidemiology. Consistent with this, parasites carrying kelch13-R561H rose to high frequency in 2020, because transmission was eliminated in all regions except the north of Kayin State, where parasites bearing this kelch13 genotype have predominated since 2017. Future surveillance will determine whether this parasite genotype is transmitted to neighboring regions, and thus related to changes in P. falciparum drug resistance dynamics on the Thailand Myanmar border. These data illustrate how genetic drift in small populations can result in instantaneous changes in the resistance status of parasite populations in near elimination settings.

genomics↗

bioRxiv2025

Chemical inhibition of a bacterial immune system

The rise of antibiotic resistance motivates a revived interest in phage therapy. However, bacteria possess dozens of anti-bacteriophage immune systems that confer resistance to therapeutic phages. Chemical inhibitors of these anti-phage immune systems could be employed as adjuvants to overcome resistance in phage-based therapies. Here, we report that anti-phage systems can be selectively inhibited by small molecules, thereby sensitizing phage-resistant bacteria to phages. We discovered a class of chemical inhibitors that inhibit the type II Thoeris anti-phage immune system. These inhibitors block the biosynthesis of a histidine-ADPR intracellular alarm signal by ThsB and prevent ThsA from arresting phage replication. These inhibitors promiscuously inhibit type II Thoeris systems from diverse bacteria--including antibiotic-resistant pathogens. Chemical inhibition of the Thoeris defense improved the efficacy of a model phage therapy against a phage-resistant strain of P. aeruginosa in a mouse infection, suggesting a therapeutic potential. Furthermore, these inhibitors may be employed as chemical tools to dissect the importance of the Thoeris system for phage defense in natural microbial communities.

biochemistry↗

bioRxiv2025

Regulation of Ordinal DNA Translocation Cycle in Bacteriophage {varphi}29 through Trans-Subunit Interactions

Certain viruses such as tailed bacteriophages and herpes simplex virus package double-stranded DNA into empty procapsids via powerful, ring-shaped molecular motors. High resolution structures and force measurements on the DNA packaging motor of bacteriophage {Phi}29 revealed that its five ATPase subunits coordinate ATP hydrolysis with each other to maintain the proper cyclic sequence of DNA translocation steps about the ring. Here, we explore how the {Phi}29 motor regulates translocation by timing key events, namely ATP binding/hydrolysis and DNA gripping, through trans-subunit interactions. We used subunit dimers bound to DNA as our model system, a minimal system that still captures the conformation and trans-subunit interactions of the full pentametric motor complex. Molecular dynamics simulations of all-ATP and mixed ATP-ADP dimers revealed that the nucleotide occupancy of one subunit strongly affects the ability to hydrolyze ATP in the adjacent subunit by altering the free energy landscape of its catalytic glutamate approaching the gamma phosphate of ATP. Specifically, one ATP-bound subunit donates residues in trans that sterically block the neighboring subunits catalytic glutamate. This steric hindrance is resolved when the first subunit hydrolyzes ATP and is ADP-bound. This obstructive mechanism is supported by functional mutagenesis and appears to be conserved across several {Phi}29 relatives. Mutual information analysis of our simulations revealed intersubunit signaling pathways, via the trans-acting obstructive residues, that allow for sensing and communication between the binding pockets of adjacent subunits. This work shows that the sequential order of DNA translocation events amongst subunits is preserved through novel trans-subunit interactions and pathways.

molecular biology↗

bioRxiv2024

Piggybacking functionalized DNA nanostructures into live cell nuclei

DNA origami (DO) are promising tools for in vitro or in vivo applications including drug delivery; biosensing, detecting biomolecules; and probing chromatin sub-structures. Targeting these nanodevices to mammalian cell nuclei could provide impactful approaches for probing visualizing and controlling important biological processes in live cells. Here we present an approach to deliver DO strucures into live cell nuclei. We show that labelled DOs do not undergo detectable structural degradation in cell culture media or human cell extracts for 24 hr. To deliver DO platforms into the nuclei of human U2OS cells, we conjugated 30 nm long DO nanorods with an antibody raised against the largest subunit of RNA Polymerase II (Pol II), a key enzyme involved in gene transcription. We find that DOs remain structurally intact in cells for 24hr, including within the nucleus. Using fluorescence microscopy we demonstrate that the electroporated anti-Pol II antibody conjugated DOs are efficiently piggybacked into nuclei and exihibit sub-diffusive motion inside the nucleus. Our results reveal that functionalizing DOs with an antibody raised against a nuclear factor is a highly effective method for the delivery of nanodevices into live cell nuclei.

bioengineering↗

bioRxiv2023

Evolution of a small phage protein confers resistance to antiphage defense in Enterococcus faecalis

The prevalence of multidrug resistant (MDR) bacterial infections continues to rise as the development of antibiotics needed to combat these infections remains stagnant. MDR enterococci are a major contributor to this crisis. A potential therapeutic approach for combating MDR enterococci is bacteriophage (phage) therapy, which uses lytic viruses to infect and kill pathogenic bacteria. While phages that lyse some strains of MDR enterococci have been identified, other strains display high levels of resistance and the mechanisms underlying this resistance are poorly defined. Here, we use a CRISPR interference (CRISPRi) screen to identify a genetic locus found on a mobilizable plasmid from Enterococcus faecalis involved in phage resistance. This locus encodes a putative serine recombinase followed by a Type IV restriction enzyme (TIV-RE) that we show restricts the replication of phage phi47 in E. faecalis. We further find that phi47 evolves to overcome restriction by acquiring a missense mutation in a TIV-RE inhibitor protein. We show that this inhibitor, termed type IV restriction inhibiting factor A (tifA), binds and inactivates diverse TIV-REs. Overall, our findings advance our understanding of phage defense in drug-resistant E. faecalis and provide mechanistic insight into how phages evolve to overcome antiphage defense systems.

microbiology↗

bioRxiv2023

Mechanism of DNA origami folding elucidated by mesoscopic simulations

DNA nanotechnology leverages the canonical base-pairing rules and geometry of DNA to create highly precise nanoscale structures with many potential applications. While the design and fabrication of DNA nanostructures is well-established, the self-assembly process that produces these structures is still poorly understood, especially for DNA origami that involve the assembly of hundreds of strands. Many experimental and computational efforts have sought to better understand DNA origami folding, but the small length and time scales of individual binding events and the long timescale over which folding occurs have posed significant challenges. Here, we present a new mesoscopic model that uses a switchable force field to capture the mechanical behavior of single- and double-stranded DNA motifs and transition between them at a coarseness level of up to 8 nucleotides per particle, allowing access to the long assembly timescales of DNA origami up to several kilobases in size. Brownian dynamics simulations of 4-helix bundle (4HB) structures using this model reveal a hierarchical folding process involving the zipping of structural domains into a partially folded precursor structure followed by gradual crystallization into the final structure. We elucidate the role of hybridization strength, scaffold routing, and staple design in the folding order and kinetics. Simulation of larger 32HB structures reveals heterogeneous staple incorporation kinetics and frequent trapping in metastable states, as opposed to smaller, more accessible structures like the 4HB, which exhibit first-order kinetics and virtually defect-free folding. The development of this model opens an avenue to better understand and design DNA nanostructures for improved yield and folding performance.

biophysics↗

bioRxiv2023

Versatile Computer Aided Design of Freeform DNA Nanostructures and Assemblies

Recent advances in structural DNA nanotechnology have been facilitated by design tools that continue to push the limits of structural complexity while simplifying an often-tedious design process. We recently introduced the software MagicDNA, which enables design of complex 3D DNA assemblies with many components; however, the design of structures with freeform features like vertices or curvature still required iterative design guided by simulation feedback and user intuition. Here, we present an updated design tool, MagicDNA 2.0, that automates the design of freeform 3D geometries, leveraging design models informed by coarse-grained molecular dynamics simulations. Our GUI-based, stepwise design approach integrates a high level of automation with versatile control over assembly and sub-component design parameters. We experimentally validated this approach by fabricating a range of DNA origami assemblies with complex freeform geometries, including a 3D Nozzle, G-clef, and Hilbert and Trifolium curves, confirming excellent agreement between design input, simulation, and structure formation.

bioengineering↗

bioRxiv2022

Steric Communication between Dynamic Components on DNA nanodevices

Biomolecular nanotechnology has helped emulate basic robotic capabilities such as defined motion, sensing, and actuation in synthetic nanoscale systems. DNA origami is an attractive approach for nanorobotics, as it enables creation of devices with complex geometry, programmed motion, rapid actuation, force application, and various kinds of sensing modalities. Advanced robotic functions like feedback control, autonomy, or programmed routines also require the ability to transmit signals among sub-components. Prior work in DNA nanotechnology has established approaches for signal transmission, for example through diffusing strands or structurally coupled motions. However, soluble communication is often slow and structural coupling of motions can limit the function of individual components, for example to respond to the environment. Here, we introduce a novel approach inspired by protein allostery to transmit signals between two distal dynamic components through steric interactions. These components undergo separate thermal fluctuations where certain conformations of one arm will sterically occlude conformations of the distal arm. We implement this approach in a DNA origami device consisting of two stiff arms each connected to a base platform via a flexible hinge joint. We demonstrate the ability for one arm to sterically regulate both the range of motion as well as the conformational state (latched or freely fluctuating) of the distal arm, results that are quantitatively captured by mesoscopic simulations using experimentally informed energy landscapes for hinge-angle fluctuations. We further demonstrate the ability to modulate signal transmission by mechanically tuning the range of thermal fluctuations and controlling the conformational states of the arms. Our results establish a communication mechanism well-suited to transmit signals between thermally fluctuating dynamic components and provide a path to transmitting signals where the input is a dynamic response to parameters like force or solution conditions.

bioengineering↗

bioRxiv2022

Thermally Reversible Pattern Formation in Arrays of Molecular Rotors

Control over the mesoscale to microscale patterning of materials is of great interest to the soft matter community. Inspired by DNA origami rotors, we introduce a 2D nearest-neighbor lattice of spinning rotors that exhibit discrete orientational states and interactions with their neighbors. Monte Carlo simulations of rotor lattices reveal that they exhibit a variety of interesting ordering behaviors and morphologies that can be modulated through rotor design parameters. The rotor arrays exhibit diverse patterns including closed loops, radiating loops, and bricklayer structures in their ordered states. They exhibit specific heat peaks at very low temperatures for small system sizes, and some systems exhibit multiple order-disorder transitions depending on inter-rotor interaction design. We devise an energy-based order parameter and show via umbrella sampling and histogram reweighting that this order parameter captures well the order-disorder transitions occurring in these systems. We fabricate real DNA origami rotors which themselves can order via programmable DNA base-pairing interactions and demonstrate both ordered and disordered phases, illustrating how rotor lattices may be realized experimentally and used for responsive organization. This work establishes the feasibility of realizing structural nanomaterials that exhibit locally mediated microscale patterns which could have applications in sensing and precision surface patterning.

biophysics↗

bioRxiv2022

Detyrosination enrichment on microtubule subsets is established by the interplay between a stochastically-acting enzyme and microtubule stability

Microtubules in cells consist of functionally diverse subpopulations carrying distinct post-translational modifications (PTMs). Akin to the histone code, the tubulin code regulates a myriad of microtubule functions ranging from intracellular transport to chromosome segregation. Yet, how individual PTMs only occur on subsets of microtubules to contribute to microtubule specialization is not well understood. In particular, microtubule detyrosination, which is the removal of the C-terminal tyrosine on -tubulin subunits, marks the stable population of microtubules and modifies how microtubules interact with other microtubule-associated proteins to regulate a wide range of cellular processes. Previously, we found that, in certain cell types, only a small subpopulation of microtubules is highly enriched with the detyrosination mark ([~]30%) and that detyrosination spans most of the length of a microtubule, often adjacent to a completely tyrosinated microtubule. How the activity of a cytosolic detyrosinase, Vasohibin (VASH) leads to only a small subpopulation of highly detyrosinated microtubules is unclear. Here, using quantitative super-resolution microscopy, we visualized nascent microtubule detyrosination events in cells consisting of 1-3 detyrosinated -tubulin subunits after Nocodazole washout. Microtubule detyrosination accumulates slowly and in a disperse pattern across the microtubule length. By visualizing single molecules of VASH in live cells, we found that VASH engages with microtubules stochastically on a short time scale suggesting limited removal of tyrosine per interaction, consistent with the super-resolution results. Combining these quantitative imaging results with simulations incorporating parameters from our experiments, we propose a stochastic model for cells to establish a subset of detyrosinated microtubules via a detyrosination-stabilization feedback mechanism.

cell biology↗

bioRxiv2022

Molecular Dynamics of DNA Translocation by FtsK

The bacterial FtsK motor harvests energy from ATP to translocate double-stranded DNA during cell division. Here, we probe the molecular mechanisms underlying coordinated DNA translocation in FtsK by performing long timescale simulations of its hexameric assembly and individual subunits. From these simulations we predict signaling pathways that connect the ATPase active site to DNA-gripping residues, which allows the motor to coordinate its translocation activity with its ATPase activity. Additionally, we utilize well-tempered metadynamics simulations to compute free-energy landscapes that elucidate the extended-to-compact transition involved in force generation. We show that nucleotide binding promotes a compact conformation of a motor subunit, whereas the apo subunit is flexible. Together, our results support a mechanism whereby each ATP-bound subunit of the motor conforms to the helical pitch of DNA, and ATP hydrolysis/product release causes a subunit to lose grip of DNA. By ordinally engaging and disengaging with DNA, the FtsK motor unidirectionally translocates DNA.

biophysics↗

bioRxiv2021

Redox sensitive E2 Rad6 controls cellular response to oxidative stress via K63 ubiquitination of ribosomes.

Protein ubiquitination is an essential process that rapidly regulates protein synthesis, function, and fate in dynamic environments. Among its non-proteolytic functions, K63 ubiquitin accumulates in yeast cells exposed to oxidative stress, stalling ribosomes at elongation. K63 ubiquitin conjugates accumulate because of redox inhibition of the deubiquitinating enzyme Ubp2, however, the role and regulation of ubiquitin conjugating enzymes in this pathway remained unclear. Here we found that the E2 Rad6 binds and modifies elongating ribosomes during oxidative stress. We elucidated a mechanism by which Rad6 and its human homolog UBE2A are redox-regulated by forming reversible disulfides with the E1 activating enzyme, Uba1. We further showed that Rad6 activity is necessary to regulate translation, antioxidant defense, and adaptation to stress. Finally, we showed that Rad6 is required to induce phosphorylation of the translation initiation factor eIF2, providing a novel link for K63 ubiquitin, elongation stalling, and the integrated stress response.

cell biology↗

bioRxiv2020

Viral Packaging ATPases Utilize a Glutamate Switch to Couple ATPase Activity and DNA Translocation

Many viruses utilize ringed packaging ATPases to translocate double-stranded DNA into procapsids during replication. A critical step in the mechanochemical cycle of such ATPases is ATP binding, which causes a subunit within the motor to grip DNA tightly. Here, we probe the underlying molecular mechanism by which ATP binding is coupled to DNA gripping and show that a glutamate switch residue found in AAA+ enzymes is central to this coupling in viral packaging ATPases. Using free energy landscapes computed through molecular dynamics simulations, we determined the stable conformational state of the ATPase active site in apo, ATP-bound, and ADP-bound states. Our results show that the catalytic glutamate residue transitions from an inactive to an active pose upon ATP binding, and that a residue assigned as the glutamate switch is necessary for regulating the transition. Further, we identified via mutual information analyses the intramolecular signaling pathway mediated by the glutamate switch that is responsible for coupling ATP binding to conformational transitions of DNA-gripping motifs. We corroborated these predictions with both structural and functional experimental data. Specifically, we showed that the crystal structure of the ADP-bound P74-26 packaging ATPase is consistent with the predicted structural coupling from simulations, and we further showed that disrupting the predicted signaling pathway indeed decouples ATPase activity from DNA translocation activity in the {varphi}29 DNA packaging motor. Our work thus establishes a signaling pathway in viral DNA packaging motors that ensures coordination between chemical and mechanical events involved in viral DNA packaging.

biophysics↗

bioRxiv2020

Atomistic Mechanism of Force Generation, Translocation, and Coordination in a Viral Genome Packaging Motor

Double-stranded DNA viruses package their genomes into pre-assembled capsids using virally-encoded ASCE ATPase ring motors. We present the first atomic-resolution crystal structure of a multimeric ring form of a viral dsDNA packaging motor and characterize its atomic-level dynamics via long timescale molecular dynamics simulations. Based on the results, we deduce an overall packaging mechanism that is driven by helical-to-planar transitions of the ring motor. These transitions are coordinated by inter-subunit interactions that regulate catalytic and force-generating events. Stepwise ATP binding to individual subunits increase their affinity for the helical DNA phosphate backbone, resulting in distortion away from the planar ring towards a helical configuration, inducing mechanical strain. Subsequent sequential hydrolysis events alleviate the accumulated mechanical strain, allowing a stepwise return of the motor to the planar conformation, translocating DNA in the process. This type of helical-to-planar mechanism could serve as a general framework for ring ATPases that exhibit burst-dwell dynamics.

molecular biology↗

bioRxiv2020

A viral genome packaging motor transitions between cyclic and helical symmetry to translocate dsDNA

Molecular segregation and biopolymer manipulation require the action of molecular motors to do work by applying directional forces to macromolecules. The additional strand conserved E (ASCE) ring motors are an ancient family of molecular motors responsible for diverse tasks ranging from biological polymer manipulation (e.g. protein degradation and chromosome segregation) to establishing and maintaining proton gradients across mitochondrial membranes. Viruses also utilize ASCE segregation motors to package their genomes into their protein capsids and serve as accessible experimental systems due to their relative simplicity. We show by CryoEM focused image reconstruction that ASCE ATPases in viral dsDNA packaging motors adopt helical symmetry complementary to their dsDNA substrates. Together with previous data, including structural results showing these ATPases in planar ring conformations, our results suggest that these motors cycle between helical and planar cyclical symmetry, providing a possible mechanism for directional translocation of DNA. We further note that similar changes in quaternary structure have been observed for proteasome and helicase motors, suggesting an ancient and common mechanism of force generation that has been adapted for specific tasks over the course of evolution.

biophysics↗