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bioRxiv2024

AdhE spirosome length in enterohaemorrhagic Escherichia coli is correlated with enzymatic directionality and is perturbed by salicylidene acylhydrazide binding

Antibiotics are contraindicated for the treatment of infection enterohemorrhagic Escherichia coli (EHEC), a human pathogen that causes diarrhea or hemorrhagic colitis in humans which can progress to hemolytic uremic syndrome (HUS). As an alternative to the use of antibiotics, previous studies developed the salicylidene acylhydrazides (SA), a family of anti-virulence compounds capable of blocking expression of the type three secretion system (T3SS), thereby reducing bacterial infections. Here we validate AdhE as the anti-virulence protein target of the SA compound ME0054. AdhE is a bidirectional enzyme able to catalyse the conversion of acetyl-CoA to ethanol and vice versa. AdhE oligomerises forming helicoidal filaments heterogeneous in length called spirosomes. In this work, we show that it is possible to partially fractionate AdhE spirosomes using size exclusion chromatography (SEC) and to characterise the spirosome oligomers present in each fraction with biophysical techniques such as small angle X-ray scattering (SAXS) and sedimentation velocity analytical ultracentrifugation (SV-AUC). Also, we observe that short spirosomes are more efficient in the reverse reaction whereas the spirosome length has no impact on the forward reaction. Therefore, for first time, we reveal that AdhE spirosome formation is necessary to regulate the direction of its enzymatic reactions. In addition, we show that ME0054 disrupts AdhE spirosomes, thereby enhancing the conversion of ethanol to acetyl-CoA. Importantly, SV-AUC data show that ME0054 binds to the AdhE filaments. Finally, time-resolved (TR) SAXS allowed us to follow the kinetics of spirosome disruption produced by ME0054, confirming its effectiveness at biologically relevant temperatures and timescales. SIGNIFICANCE STATEMENTThere is an urgent need to develop alternative strategies to combat bacterial infections. Salicylidene acylhydrazides (SA) are able to reduce expression of the bacterial type three secretion system (T3SS), used by many pathogens to manipulate host eukaryotic cells, including our pathogen of interest: enterohaemorrhagic E. coli (EHEC). The mechanism underpinning these compounds is a mystery. Here we show how the SA compound ME0054, by disrupting AdhE spirosomes, enhances metabolic conversion of ethanol to acetyl-CoA. This finding is consistent with the phenotype observed in an EHEC AdhE mutant: alterations in acetate levels and changes in T3SS expression. Our work establishes a crucial mechanistic link between the binding of the SA compound to a key target protein and changes in bacterial metabolism.

biophysics↗

bioRxiv2024

A practical guide to time-resolved fluorescence microscopy and spectroscopy

Time-correlated single photon counting (TCSPC) coupled with confocal microscopy is a versatile biophysical tool that enables real-time monitoring of biomolecular dynamics across many timescales. With TCSPC, Fluorescence correlation spectroscopy (FCS) and pulsed interleaved excitation-Forster resonance energy transfer (PIE-FRET) are collected simultaneously on diffusing molecules to extract diffusion characteristics and proximity information. This article is a guide to calibrating FCS and PIE-FRET measurements with several biological samples including liposomes, streptavidin-coated quantum dots, proteins, and nucleic acids for reliable determination of diffusion coefficients and FRET efficiency. The FRET efficiency results are also compared to surface-attached single molecules using fluorescence lifetime imaging microscopy (FLIM-FRET). Combining the methods is a powerful approach to revealing mechanistic details of biological processes and pathways.

biophysics↗

bioRxiv2024

In Silico Study of the Early Stages of Aggregation of β-Sheet Forming Antimicrobial Peptide GL13K

Antimicrobial peptides (AMPs) are of growing interest as potential candidates for antibiotics to which antimicrobial resistance increases slowly. In this article, we perform the first in silico study of the synthetic {beta} sheet-forming AMP GL13K. Through atomistic simulations of single and multipeptide systems under different charge conditions, we are able to shine a light on the short timescales of early aggregation. We find that isolated peptide conformations are primarily dictated by sequence rather than charge, whereas changing charge has a significant impact on the conformational free energy landscape of multi-peptide systems. We demonstrate that the lack of charge-charge repulsion is a sufficient minimal model for experimentally observed aggregation. Overall, our work explores the molecular biophysical underpinnings of the first stages of aggregation of a unique AMP, laying necessary groundwork for its further development as an antibiotic candidate.

biophysics↗

bioRxiv2024

Cost-benefit analysis of cryogenic electron tomography subtomogram averaging of chaperonin MmCpn at near atomic resolution.

Cryogenic electron microscopy single particle reconstruction (cryoEM-SPR) has evolved into a routine approach for determining macromolecule structures to near-atomic resolution. Cryogenic electron tomography subtomogram averaging (cryoET-STA) towards similar resolution, in contrast, is still under active development. CryoET can capture the 3D snapshot of individual macromolecules by stage tilting, offering multiple angular views per particle than the single particle reconstruction approach. Here we use the archaea chaperonin MmCpn as a model macromolecule to investigate the resolution limiting factors of cryoET-STA in terms of cumulative electron dose, ice thickness, subtomogram numbers and tilt angle ranges. By quantitative analysis of these factors against the STA reconstruction resolution, we delineate the feasibility of attaining high resolution structure determination with cryoET-STA. This study provides biophysical guidance for the application of cryoET-STA towards high resolution and the cost against benefit of using cryoET-STA to achieve an efficient outcome at the desired resolution.

biophysics↗

bioRxiv2024

Distinct platelet interactions with soluble and immobilized von Willebrand factor modulate platelet adhesion and aggregation with differential impact on hemostasis and thrombosis

Arterial thrombosis is a prevailing and lethal pathological condition that remains difficult to treat or prevent without potentially serious side effects, mostly hemorrhagic in nature. Platelets and von Willebrand factor (VWF) have a recognized major role in the pathogenesis of arterial thrombosis. Platelets bind to surface immobilized VWF for initial adhesion to injured vascular sites, but also interact with soluble VWF to aggregate into thrombi, particularly under flow conditions creating elevated shear stress. Whether the binding of immobilized and soluble VWF to platelets is regulated by separate mechanisms and how they respectively regulate hemostasis and thrombosis remains unclear. Using targeted mutagenesis we engineered VWF to achieve modified binding kinetics with the platelet receptor glycoprotein (GP) Ib and discovered that the interactions of immobilized and soluble VWF with platelets can be differentially regulated with distinct consequences on platelet adhesion and aggregation. Based on these results, we studied a monoclonal antibody, NMC4, known to bind to an epitope in the VWFA1 domain and to inhibit preferentially platelet aggregation under elevated shear stress conditions. We found that NMC4 was less efficient in reducing platelet adhesion to immobilized VWF than platelet aggregation mediated by soluble VWF and, surprisingly, also inhibited arterial thrombosis in a mouse model of ferric chloride-induced carotid artery occlusion at a dose that failed to prolong post-injury bleeding. Thus, our current findings help delineate interrelated biochemical and biophysical mechanisms underlying VWF function in vascular health; and suggest selective inhibition of VWF-mediated platelet aggregation as opposed to adhesion as a strategy to prevent arterial thrombosis while minimizing bleeding complications.

biophysics↗

bioRxiv2024

Interplay between cortical adhesion and membrane bending regulates microparticle formation

The formation of blebs and microparticle formation requires the bending of the plasma membrane away from the cytosol. There are multiple factors that control the formation of the microparticles including the loss of lipid asymmetry, primarily the exposure of phosphatidylserine on the outer leaflet, detachment of the membrane from the cortical cytoskeleton, and bleb expansion due to pressure. In this work, we develop a biophysical model that accounts for the interaction between these different factors. Our findings reveal that linker attachment is a key determinant of outward budding and lays out the mechanical aspects of outward budding of the plasma membrane. Significance StatementCells release many types of membrane-enclosed vesicles in response to stress, inflammation, or other injuries. Formation of these membrane-enclosed structures is critical for proper function of the coagulation cascade and apoptosis. In many cases, these microparticles are also a part of the long distance intercellular communication and are implicated in chemoresistance. A particular class of vesicles called ectosomes or microparticles are released by the outward budding of the plasma membrane, a process which requires detachment of the membrane from the cortex, exposure of negatively charged, curvature-inducing lipids such as phosphatidylserine from the inner leaflet to the outer leaflet, and pressure-driven expansion of the bleb. Here, we used membrane mechanics coupled with the kinetics of adhesive linker binding-unbinding to investigate how these different factors interact together. Using our models, we predict how linker properties plays an important role in the outward budding of the plasma membrane and identify conditions that can promote or inhibit such curvature generation. These findings have implications not just for conditions that require successful microparticle formation such as the procoagulation cascade but also for inhibiting microparticle formation in cases of chemoresistant drug efflux by tumor cells.

biophysics↗

bioRxiv2024

Metal ion activation and DNA recognition by the Deinococcus radiodurans manganese sensor DR2539

The accumulation of manganese ions is crucial for scavenging reactive oxygen species (ROS) and protecting the proteome of Deinococcus radiodurans (Dr). However, metal homeostasis still needs to be tightly regulated to avoid toxicity. DR2539, a dimeric transcription regulator, plays a key role in Dr manganese homeostasis. Despite comprising three well-conserved domains: a DNA binding domain, a dimerization domain, and an ancillary domain, both the metal ion activation mechanism and the DNA recognition mechanism remain elusive. In this study, we present biophysical analyses and the structure of the dimerization and DNA binding domains of DR2539 in its holo form and in complex with the 21 bp pseudo-palindromic repeat of the dr1709 promotor region. These findings shed light into the activation and recognition mechanisms. The dimer presents eight manganese binding sites that induce structural conformations essential for DNA binding. The analysis of the protein-DNA interfaces elucidates the significance of Tyr59 and helix H3 sequence in the interaction with the DNA. Finally, the structure in solution as determined by small angle X-ray scattering experiments and supported by AlphaFold modelling provides a model illustrating the conformational changes induced upon metal binding.

biophysics↗

bioRxiv2024

Quantitative model and physical mechanisms of iRBC membrane curling during egress of malaria parasites

Egress of malaria merozoites from infected red blood cells (iRBC) is a critical step in the parasites life cycle. The egress is accompanied by the formation of a pore in the erythrocyte membrane, followed by an outward curling of the membrane around the pore, resulting in a complete eversion of the erythrocyte membrane, pushing the parasites away. Despite the well-documented steps of the egress, the detailed mechanism and source of energy for such a spectacular eversion of iRBC remains largely unknown. In this paper, we consider a biophysical model based on the energetics of the egress process that includes both viscous dissipation and energy consumption for the formation of the rim around the pore in iRBC. We show that viscosity does not play a significant role in iRBC eversion and we hypothesize that this process is controlled by lateral lipid diffusion. The model is supported by quantitative estimates and is in good agreement with known experimental data.

biophysics↗

bioRxiv2024

Evidence for a transfer-to-trap mechanism of fluorophore concentration quenching in lipid bilayers

It is important to understand the behaviours of fluorescent molecules because, firstly, they are often utilized as probes in biophysical experiments and, secondly, they are crucial cofactors in biological processes such as photosynthesis. A phenomenon called fluorescence quenching occurs when fluorophores are present at high concentrations but the mechanisms for quenching are debated. Here, we used a technique called in-membrane electrophoresis to generate concentration gradients of fluorophores within a supported lipid bilayer (SLB), across which quenching was expected to occur. Fluorescence lifetime imaging microscopy (FLIM) provides images where the fluorescence intensity in each pixel is correlated to fluorescence lifetime: the intensity provides information about the location and concentration of fluorophores and the lifetime reveals the occurrence of energy-dissipative processes. FLIM was used to compare the quenching behaviour of three commonly-used fluorophores: Texas Red (TR), nitrobenzoaxadiazole (NBD) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY). FLIM images provided evidence of quenching in regions where the fluorophores accumulated but the degree of quenching varied between the different fluorophores. The relationship between quenching and concentration was quantified and the critical radius for trap formation, representing the relative quenching strength, was calculated as 2.70, 2.02 and 1.14 nm, for BODIPY, TR and NBD, respectively. The experimental data supports the theory that quenching takes place via a transfer-to-trap mechanism which proposes, firstly, that excitation energy is transferred between fluorophores and may reach a trap site resulting in immediate energy dissipation and, secondly, that trap sites are formed in a concentration-dependent manner. Some previous work suggested that quenching occurs only when fluorophores aggregate, or form long-lived dimers, but our data and this theory argues that traps may be statistical pairs of fluorophores that exist only transiently. Our findings should inspire future work to assess whether these traps can be charge-transfer states, excited state dimers or something else.

biophysics↗

bioRxiv2024

A comprehensive map of transient protein-protein interactions and their structural features in the E. coli 1-carbon metabolism pathway

Enzymes in a pathway often form metabolons through weak protein-protein interactions (PPI) that localize and protect labile metabolites. Due to their transient nature, the structural architecture of these enzyme assemblies has largely remained elusive, limiting our abilities to re-engineer novel metabolic pathways. Here we delineate a complete PPI map of 1225 interactions in the E. coli 1-carbon metabolism pathway using bimolecular fluorescence complementation that can capture transient interactions in vivo and show strong intra- and inter-pathway clusters within the folate and purine biosynthesis pathways. Scanning mutagenesis experiments along with AlphaFold predictions and meta-dynamics simulations reveal that most proteins use conserved "dedicated" interfaces distant from their active sites to interact with multiple partners. Diffusion-reaction simulations with shared interaction surfaces and realistic PPI networks reveal a dramatic speedup in metabolic pathway fluxes. Overall, this study sheds light on the fundamental features of metabolon biophysics and structural aspects of transient binary complexes. Significance statementEnzymes from the same metabolic pathway often form dynamic assemblies called metabolons, which channel metabolites as well as protect labile intermediates. Yet very little is known about their structural features or what makes these interactions transient. Paucity of such information has particularly affected our ability to engineer novel metabolic pathways, construct multi-scale mathematical models of cells, etc. We address this by obtaining a comprehensive map for 1225 interaction pairs in the essential 1-carbon metabolism pathway of E. coli. Using both high-throughput experiments and computation, we uncover that metabolon proteins tend to use a conserved dedicated interface to interact with their partners. These results shed light on structural and energetic aspects of PPI in metabolons at near atomic level of resolution.

biophysics↗

bioRxiv2024

The Strongest Protein Binder is Surprisingly Labile

Bacterial adhesins are cell-surface proteins that anchor to the cell wall of the host, thus initiating infection. The initial step in infection is precisely the binding to fibrinogen (Fg) from human tissue, after which bacteria can colonize the heart valves by the formation of biofilms. The study of this family of proteins is hence essential to develop new strategies to fight bacterial infections. In the case of Staphylococcus aureus, there exists a type of adhesins known as Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs). Here, we focus on one of them, the Clumping Factor A (ClfA), which has been found to bind Fg through the dock-lock-latch (DLL) mechanism. Interestingly, it has recently been discovered that MSCRAMMs proteins employ a catch-bond to withstand forces exceeding 2 nN, making this type of interaction as mechanically strong as a covalent bond. However, whether this strength is an evolved feature characteristic of the bacterial protein or is typical only of the interaction with its partner is not known. Here we combine single-molecule force spectroscopy (smFS), biophysical binding assays and molecular simulations to study the intrinsic mechanical strength of ClfA. We find that despite the extremely high forces required to break its interactions with Fg, ClfA is not by itself particularly strong, in the absence of its human target. Integrating the results from both theory and experiments we dissect contributions to the mechanical stability of this protein.

biophysics↗

bioRxiv2024

Time Resolved Inspection of Ionizable-Lipid Facilitated Lipid Nanoparticle Disintegration and Cargo Release at an Endosomal Membrane Mimic

This study investigates pH-triggered fusion dynamics of lipid nanoparticles (LNPs) with an endosomal membrane mimic, addressing mechanistic aspects of a crucial yet elusive process for effective mRNA delivery. Utilizing time-resolved total internal reflection fluorescence (TIRF) imaging, we observed a delayed onset of LNP fusion upon pH drop, lasting seconds to minutes depending on pH and LNP size. Once initiated, LNP fusion and cargo escape occurred rapidly within tens to hundreds of milliseconds. While LNP disintegration is observed to lead to release of a significant portion of mRNA into the acidic environment, some mRNA molecules remained mobile on the endosomal membrane mimic due to deprotonation-resistant complex salt formation. Comparison of the fusion efficiency of two LNP formulations correlated with protein translation in human primary cell transfection data, emphasizing the importance of biophysical investigations in understanding ionizable-lipid-containing LNP-assisted mRNA delivery mechanisms and providing insights for optimizing mRNA-LNP design for enhanced endosomal escape.

biophysics↗

bioRxiv2024

Decoding the role of DNA sequence on protein-DNA co-condensation

The eukaryotic genome is organized within the cell nucleus through three-dimensional compaction. The physical principles that govern genome organization in vivo remain less understood. Phase separation of protein and DNA has emerged as an attractive mechanism for reshaping chromatin and compacting the genome. In vitro studies have shed light on the biophysical principles of protein-DNA condensates driven by protein-protein and protein-DNA interactions. However, the role of DNA sequence and its impact on protein-DNA condensation remains elusive. Guided by experiments, this paper presents a simple polymer-based model of protein-mediated DNA condensation that explicitly incorporates the influence of DNA sequence on protein binding. Using coarse-grained Brownian dynamics simulations, we demonstrate that, in the case of a homogeneous DNA, only one condensate forms in equilibrium. In sharp contrast, DNA sequence heterogeneity can result in the coexistence of multiple condensates, giving rise to the formation of structures resembling pearl-necklaces. Interestingly, we observe that protein binding affinity of interfacial DNA governs the capillary forces arising from the protein-DNA condensates. To demonstrate the usefulness of our modeling framework, we compare the simulation results against published data for co-condensation of Dps, Sox2, and HP1. We find that while Dps exhibits sequence-independent binding, DNA sequence heterogeneity dictates the co-condensation of Sox2 and HP1 with DNA. Overall, the framework developed here can be harnessed to gain mechanistic insights into the role of DNA sequence on protein-DNA co-condensation and pave the way for developing a deeper understanding of genome organisation.

biophysics↗

bioRxiv2024

Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy

-Klotho (KLA) is a type-1 membranous protein that can associate with fibroblast growth factor receptor (FGFR) to form co-receptor for FGF23. The ectodomain of unassociated KLA is shed as soluble KLA (sKLA) to exert FGFR/FGF23-independent pleiotropic functions. The previously determined X-ray crystal structure of the extracellular region of sKLA in complex with FGF23 and FGFR1c suggests that sKLA functions solely as an on-demand coreceptor for FGF23. To understand the FGFR/FGF23-independent pleiotropic functions of sKLA, we investigated biophysical properties and structure of apo-sKLA. Mass photometry revealed that sKLA can form a stable structure with FGFR and/or FGF23 as well as sKLA dimer in solution. Single particle cryogenic electron microscopy (cryo-EM) supported the dimeric structure of sKLA. Cryo-EM further revealed a 3.3[A] resolution structure of apo-sKLA that overlays well with its counterpart in the ternary complex with several distinct features. Compared to the ternary complex, the KL2 domain of apo-sKLA is more flexible. 3D variability analysis revealed that apo-sKLA adopts conformations with different KL1-KL2 interdomain bending and rotational angles. The potential multiple forms and shapes of sKLA support its role as FGFR-independent hormone with pleiotropic functions. A comprehensive understanding of the sKLA conformational landscape will provide the foundation for developing klotho-related therapies for diseases.

biophysics↗

bioRxiv2024

Prediction of Ca2+ binding site in proteins with a fast and accurate method based on statistical mechanics and analysis of crystal structures

Predicting the precise locations of metal binding sites within metalloproteins is a crucial challenge in biophysics. A fast, accurate, and interpretable computational prediction method can complement the experimental studies. With this endeavor, In the current work, we have developed a method to predict the location of Ca2+ ions in calcium-binding proteins using a physics-based method with an all-atom description of the proteins, which is substantially faster than the molecular dynamics simulation-based methods with accuracy as good as data-driven approaches. Our methodology uses the three-dimensional reference interaction site model (3D-RISM), a statistical mechanical theory, to calculate Ca2+ ion density around protein structures, and the locations of the Ca2+ ions are obtained from the density. We have taken previously used datasets to assess the efficacy of our method as compared to previous works. Our accuracy is found to be 88%, comparable with the FEATURE program, one of the well-known data-driven methods. Moreover, our method being physical, the reasons for failures can be ascertained in most cases. We have thoroughly examined the failed cases using different structural and crystallographic measures, such as B-factor, R-factor, electron density map, and geometry at the binding site. It has been found that X-ray structures have issues in many of the failed cases, such as geometric irregularities and dubious assignment of ion positions. Our algorithm, along with the checks for structural accuracy, is a major step in predicting calcium ion positions in metalloproteins.

biophysics↗

bioRxiv2024

An Allosteric Cholesterol Site in Glycine Receptors Characterized Through Molecular Simulations

Glycine receptors are pentameric ligand-gated ion channels that conduct chloride ions across postsynaptic membranes to facilitate fast inhibitory neurotransmission. In addition to gating by the glycine agonist, interactions with lipids and other compounds in the surrounding membrane environment modulate their function, but molecular details of these interactions remain unclear - in particular for cholesterol. To identify such interactions, here we report on coarse-grained simulations in a model neuronal membrane for three zebrafish glycine-receptor structures, representing apparent resting, open, and desensitized states. We then converted the systems to all-atom models to examine detailed lipid interactions, and observe cholesterol bound to the receptor at an outer-leaflet intersubunit site in a state-dependent manner, indicating that it can bias receptor function. Finally, using a modified perturbation-response scanning approach, we applied short atomistic simulations to identify amino-acid translations correlated with gating conformational changes. Frequent cholesterol contacts in atomistic simulations clustered with residues identified by perturbation analysis and overlapped with mutations influencing channel function and pathology. Cholesterol binding at this site was also observed in a recently reported pig heteromeric glycine receptor. These results indicate state-dependent lipid interactions relevant to allosteric transitions of heteromeric glycine receptors, including specific amino-acid contacts applicable to biophysical modeling and pharmaceutical design.

biophysics↗

bioRxiv2024

Dilated cardiomyopathy-associated skeletal muscle actin (ACTA1) mutation R256H disrupts actin structure and function and causes cardiomyocyte hypocontractility

Skeletal muscle actin (ACTA1) mutations are a prevalent cause of skeletal myopathies consistent with ACTA1s high expression in skeletal muscle. Rare de novo mutations in ACTA1 associated with combined cardiac and skeletal myopathies have been reported, but ACTA1 represents only [~]20% of the total actin pool in cardiomyocytes, making its role in cardiomyopathy controversial. Here we demonstrate how a mutation in an actin isoform expressed at low levels in cardiomyocytes can cause cardiomyopathy by focusing on a unique ACTA1 mutation, R256H. We previously identified this mutation in multiple family members with dilated cardiomyopathy (DCM), who had reduced systolic function without clinical skeletal myopathy. Using a battery of multiscale biophysical tools, we show that R256H has potent functional effects on ACTA1 function at the molecular scale and in human cardiomyocytes. Importantly, we demonstrate that R256H acts in a dominant manner, where the incorporation of small amounts of mutant protein into thin filaments is sufficient to disrupt molecular contractility, and that this effect is dependent on the presence of troponin and tropomyosin. To understand the structural basis of this change in regulation, we resolved a structure of R256H filaments using Cryo-EM, and we see alterations in actins structure that have the potential to disrupt interactions with tropomyosin. Finally, we show that ACTA1R256H/+ human induced pluripotent stem cell cardiomyocytes demonstrate reduced contractility and sarcomeric disorganization. Taken together, we demonstrate that R256H has multiple effects on ACTA1 function that are sufficient to cause reduced contractility and establish a likely causative relationship between ACTA1 R256H and clinical cardiomyopathy. Significance StatementSkeletal muscle actin mutations are well-known to cause skeletal myopathies, but their role in cardiomyopathies have been controversial as skeletal muscle actin is only expressed at modest levels in the heart. Here, we demonstrate that a skeletal muscle actin mutation potently causes multiple defects in actin function at the atomic and molecular scales, and it functions in a dominant fashion, leading to cardiomyocyte contractile defects. Our results establish how skeletal muscle actin mutations may cause cardiomyocyte dysfunction and lay the foundation for future studies of the role of skeletal muscle actin in cardiomyopathy.

biophysics↗

bioRxiv2024

A metastasis-associated Pannexin1 mutant (Panx11-89) forms a minimalist ATP release channel

A truncated form of the ATP release channel pannexin 1 (Panx1), Panx11-89, is enriched in metastatic breast cancer cells and has been proposed to mediate metastatic cell survival by increasing ATP release through mechanosensitive Panx1 channels. However, whether Panx11-89 on its own (without the presence of wtPanx1) mediates ATP release has not been tested. Here, we show that Panx11-89 by itself can form a constitutively active membrane channel, capable of releasing ATP even in the absence of wild type Panx1. Our biophysical characterization reveals that most basic structure-function features of the channel pore are conserved in the truncated Panx11-89 peptide. Thus, augmenting extracellular potassium ion concentrations enhances Panx11-89-mediated conductance. Moreover, despite the severe truncation, Panx11-89 retains the sensitivity to most of wtPanx1 channel inhibitors and can thus be targeted. Therefore, Panx1 blockers have the potential to be of therapeutic value to combat metastatic cell survival. Our study not only elucidates a mechanism for ATP release from cancer cells, but it also supports that the Panx11-89 mutant should facilitate structure-function analysis of Panx1 channels.

biophysics↗