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bioRxiv2022

Comparative sub-cellular proteome analyses reveals metabolic differentiation and production of effector-like molecules in the dieback phytopathogen Phytophthora cinnamomi.

Phytopathogenic oomycetes pose a significant threat to global biodiversity and food security. The proteomes of these oomycetes likely contain important factors that contribute to their pathogenic success, making their discovery crucial for elucidating pathogenicity. Oomycetes secrete effector proteins that overcome or elicit a defence response in susceptible hosts. Phytophthora cinnamomi is a root pathogen that causes dieback in a wide variety of crops and a range of native vegetation world-wide. Virulence proteins produced by P. cinnamomi are not well defined and a large-scale approach to understand the biochemistry of this pathogen has not been documented. Here, soluble mycelial, zoospore and secreted proteomes were obtained and label-free quantitative proteomics was used to compare the composition of protein content of the three sub-proteomes by matching the MS/MS data to a sequenced P. cinnamomi genome. Mass spectra matched to a total of 4635 proteins, validating 17.7% of the predicted gene set of the P. cinnamomi genome. The mycelia were abundant in transporters for nutrient acquisition, metabolism and cellular proliferation. The zoospores had less metabolic related ontologies than the mycelia but were abundant in energy generating, motility and signalling associated proteins. Virulence-associated proteins were identified in the secretome such as candidate effector and effector-like proteins, which interfere with the host immune system. These include hydrolases, cell wall degrading enzymes, putative necrosis-inducing proteins and elicitins. The secretome elicited a hypersensitive response on the roots of a model host and thus suggests evidence of effector activity. SignificancePhytophthora cinnamomi is a phytopathogenic oomycete that causes dieback disease in native vegetation and several horticultural crops such as avocado, pineapple and macadamia. Whilst this pathogen has significance world-wide, its pathogenicity and virulence have not been described in depth. We carried out comparative label-free proteomics of the mycelia, zoospores and secretome of P. cinnamomi. This study highlights the differential metabolism and cellular processes between the sub-proteomes. Proteins associated with metabolism, nutrient transport and cellular proliferation were over represented in the mycelia. The zoospores have a specialised proteome showing increased energy generation geared towards motility. Candidate effectors and effector-like secreted proteins were also identified, which can be exploited for genetic resistance. This demonstrates a better understanding of the biology and pathogenicity of P. cinnamomi infection that can subsequently be used to develop effective methods of disease management

biochemistry↗

bioRxiv2022

Allosteric interactions prime androgen receptor dimerization and activation

The androgen receptor (AR) is a steroid receptor and master transcription factor that governs gene expression programs required for luminal development of prostate epithelium, formation of muscle tissue and maintenance of the male phenotype. AR misregulation is a hallmark of multiple malignancies, including prostate cancer, where AR hyperactivation and expansion of its transcriptome occur in part through AR gene amplification and interaction with oncoprotein cofactors. Despite its biological importance, how ARs individual domains and its protein cofactors cooperate to bind DNA have remained elusive. Using a combination of reconstitution biochemistry and single particle cryo-electron microscopy (EM), we have isolated three conformational states of AR bound to DNA. We observe that AR forms a non-obligate dimer, with the buried dimer interface utilized by related ancestral nuclear receptors repurposed to facilitate cooperative DNA binding. We identify surfaces bridging ARs domains responsible for allosteric communication, that are compromised in partial androgen insensitivity syndrome (PAIS), and are reinforced by ARs oncoprotein cofactor, ERG, and DNA binding site motifs. Finally, we present evidence that this plastic dimer interface for transcriptional activation may have been adopted by AR at the expense of DNA binding. Our work highlights how fine-tuning of ARs cooperative interactions translate to consequences in development and disease.

biochemistry↗

bioRxiv2022

Divergent kinase WNG1 is regulated by phosphorylation of an atypical activation sub-domain

Apicomplexan parasites like Toxoplasma gondii grow and replicate within a specialized organelle called the parasitophorous vacuole. The vacuole is decorated with parasite proteins that integrate into the membrane after trafficking through the parasite secretory system as soluble, chaperoned complexes. A regulator of this process is an atypical protein kinase called WNG1. Phosphorylation by WNG1 appears to serve as a switch for membrane integration. However, like its substrates, WNG1 is secreted from the parasite dense granules, and its activity must therefore be tightly regulated until the correct membrane is encountered. Here we demonstrate that, while another member of the WNG family can adopt multiple multimeric states, WNG1 is monomeric and therefore not regulated by multimerization. Instead, we identify two phosphosites on WNG1 that are required for its kinase activity. Using a combination of in vitro biochemistry and structural modeling, we identify basic residues that are also required for WNG1 activity and therefore appear to recognize the activating phosphosites. Among these coordinating residues are the "HRD" Arg, which recognizes activation loop phosphorylation in canonical kinases. WNG1, however, is not phosphorylated on its activation loop, and its activating phosphosites instead appear to lock the kinase C-lobe into an activated conformation. These data suggest a simple model for WNG1 activation by increasing ATP concentration above a critical threshold once WNG1 traffics to the parasitophorous vacuole.

biochemistry↗

bioRxiv2022

A multidisciplinary analysis of the as-isolated Escherichia coli SufBC2D complex reveals the presence of two new iron-sulfur clusters

Iron-sulfur (Fe-S) clusters are essential inorganic cofactors dedicated to a wide range of biological functions including electron transfer and catalysis. Specialized multi-protein machineries present in all types of organisms support their biosynthesis. These machineries encompass a scaffold protein on which Fe-S clusters are assembled before being transferred to cellular targets. Here, we describe the first characterization of the native Fe-S cluster of the anaerobically purified SufBC2D scaffold from Escherichia coli by XAS, Mossbauer, UV-visible absorption and EPR spectroscopy. Interestingly, we propose that SufBC2D harbors two types of Fe-S cluster, a [2Fe-2S] cluster with an unprecedented usual coordination and a previously unreported [3Fe-3S] cluster. These data combined with mutagenesis and biochemistry allow to propose ligands for these clusters. These results support the hypothesis that both SufB and SufD are involved in Fe-S cluster ligation and are discussed in the context of Fe-S cluster biogenesis where both [2Fe-2S] and [4Fe-4S] clusters need to mature cellular Fe-S protein targets.

biochemistry↗

bioRxiv2022

Structure of phage lambda Red-beta(177) annealase shows how it anneals DNA strands during single-strand annealing homologous DNA recombination

The bacteriophage {lambda} red recombination system catalyzes the single-strand annealing homologous DNA recombination reaction, in which Red{beta} annealase protein plays a critical role. Using cryogenic electron microscopy, we were able to determine a structure of a C-terminally truncated Red{beta} with the residues 1-177 bound to two complementary 27mer oligonucleotides forming an annealing intermediate, to a final resolution of 3.3 [A]. This structure validates and rationalizes decades of experimental observations on the biochemistry of Red{beta}. Definition of the interaction surfaces between subunits explains not only the DNA binding properties of Red{beta}, but also its propensity to oligomerize into long helical filaments, which are also formed by almost all annealases and are known to be functionally important. In addition, this annealing intermediate structure provides a detailed picture of the hydrogen bonding network that positions the DNA strands in a planar orientation to facilitate base pairing. Residues 133-138, which are missing from our structure, form a flexible loop. Molecular dynamics simulations were used to model the range of motion of the flexible loop, which suggested that it has a crucial role in keeping the DNA strands in the DNA-binding groove long enough to allow homology searching. The combination of structural and computational observations has allowed us to propose a detailed mechanism for the action of Red{beta}. More than half a century after its discovery, our work shines a light not only on the structure and mechanisms of Red{beta}, but also of other proteins within the annealase superfamilies. Significance StatementSingle-strand annealing homologous DNA recombination is a process that is conserved throughout evolution from bacteriophages to humans, highlighting its importance and indispensability. It is a process that repairs double-stranded DNA breaks and is particularly vital in dsDNA viruses. The Red{beta} protein from the bacteriophage lambda is the archetypal annealase protein, forming the basis of our knowledge about this class of proteins. Along with the exonuclease {lambda}Exo, these two proteins not only form the model system for single-strand annealing homologous recombination, but are also used in thousands of laboratories worldwide for performing genetic manipulations. After its discovery in 1966, we report the first structure of the DNA-binding and oligomerization domain of Red{beta}, providing details about the mechanism of homologous DNA annealing.

biochemistry↗

bioRxiv2022

Redox-controlled structural reorganization and flavin strain within the ribonucleotide reductase R2b-NrdI complex monitored by serial femtosecond crystallography

Redox reactions are central to biochemistry and are both controlled by and induce protein structural changes. Here we describe structural rearrangements and crosstalk within the Bacillus cereus ribonucleotide reductase R2b-NrdI complex, a di-metal carboxylate- flavoprotein system, as part of the mechanism generating the essential catalytic free radical of the enzyme. Femtosecond crystallography at an X-ray free-electron laser was utilized to obtain structures at room temperature in defined redox states without suffering photoreduction. We show that the flavin in the hydroquinone state is under steric strain in the R2b-NrdI protein complex, presumably tuning its redox potential to promote superoxide generation. Moreover, a binding site in close vicinity to the expected flavin O2-interacton site is observed to be controlled by the redox state of the flavin and linked to the channel proposed to funnel the produced superoxide species from NrdI to the di-manganese site in protein R2b. These specific features are coupled to further structural changes around the R2b- NrdI interaction surface. The mechanistic implications for the control of reactive oxygen species and radical generation in protein R2b are discussed.

biochemistry↗

bioRxiv2022

Mechanism of threonine ADP-ribosylation of F-actin by a Tc toxin

Tc toxins deliver toxic enzymes into host cells by a unique injection mechanism. One of these enzymes is TccC3, an ADP-ribosyltransferase from Photorhabdus luminescens. Once TccC3 is translocated into the target cell, the enzyme ADP-ribosylates actin, resulting in clustering of the actin cytoskeleton and ultimately cell death. Here, we combine biochemistry, solution and solid-state NMR spectroscopy and cryo-EM to show in atomic detail how TccC3 modifies actin. We find that the ADP-ribosyltransferase does not bind to G-actin but interacts with two consecutive actin subunits of F-actin. The binding of TccC3 to F-actin occurs via an induced-fit mechanism that facilitates access of NAD+ to the nucleotide binding pocket. The following nucleophilic substitution reaction results in the transfer of ADP-ribose to threonine-148 of F-actin. We demonstrate that this site-specific modification of F-actin prevents its interaction with depolymerization factors, such as cofilin, which impairs actin network turnover and leads to steady actin polymerization. Our findings reveal in atomic detail a new mechanism of action of a bacterial toxin through specific targeting and modification of F-actin.

biochemistry↗

bioRxiv2022

Human RAD52 stimulates the RAD51-mediated homology search

Homologous recombination (HR) is a DNA repair mechanism of double strand breaks and blocked replication forks that involves a process of homology search and homologous pairing leading to the formation of synaptic intermediates whose architecture and dynamics are tightly regulated to ensure genome integrity. In this mechanism, RAD51 recombinase plays a central role and is supported by many partner including BRCA2 and RAD52. If the mediator function of BRCA2 to load RAD51 on RPA-covered ssDNA is well established, the role of RAD52 in HR, more precisely its interplay with BRCA2 is still far from understood. We have used Transmission Electron Microscopy combined with biochemistry to characterize the sequential participation of RPA, RAD52 and BRCA2 in the assembly of the RAD51 filament, its architecture and its activity. Despite our results confirm that RAD52 lacks a mediator activity, we observed that RAD52 can tightly bind to RPA-coated ssDNA, inhibit the mediator role of BRCA2 and form shorter RAD52- and RAD51-containing mixed filaments that are more efficient in subsequent homology search and formation of synaptic complexes and D-loops, resulting in more frequent multi-invasions as well. Through the characterization of the behavior of RAD52 and BRCA2, these results provide new molecular insights on the formation and regulation of presynaptic and synaptic intermediates during human HR.

biochemistry↗

bioRxiv2022

Structure of the catalytically active APOBEC3G bound to a DNA oligonucleotide inhibitor reveals tetrahedral geometry of the transition state

APOBEC3 proteins (A3s) are enzymes that catalyze deamination of cytidine to uridine in single-stranded DNA (ssDNA) substrates, thus playing a key role in innate antiviral immunity. However, APOBEC3 family has also been linked to many mutational signatures in cancer cells, which has led to intense interest to develop inhibitors of A3s catalytic activity as therapeutics as well as tools to study A3s biochemistry, structure and cellular function. Recent studies have shown that ssDNA containing 2'-deoxy-zebularine (dZ-ssDNA) is an inhibitor of A3s such as A3A, A3B and A3G, although atomic determinants of this activity remained unknown. To fill this knowledge gap, we determined a 1.5 [A] resolution structure of a dZ-ssDNA inhibitor bound to active A3G. The crystal structure revealed that the activated dZ/H2O mimics the transition state by coordinating the active site Zn2+ and engaging in additional stabilizing interactions, such as the one with the catalytic residues E259. Therefore, this structure allowed us to capture the first snapshot of the A3s transition state, and suggests that developing transition-state mimicking inhibitors may provide a new opportunity to design more targeted molecules for A3s in the future.

biochemistry↗

bioRxiv2022

Evolutionary and cellular analysis of the dark pseudokinase PSKH2

Pseudokinases, so named because they lack one or more conserved canonical amino acids that define their catalytically-active relatives, have evolved a variety of biological functions in both prokaryotic and eukaryotic organisms. Human PSKH2 is closely related to the canonical kinase PSKH1, which maps to the CAMK family of protein kinases. Primates encode PSKH2 in the form of a pseudokinase, which is predicted to be catalytically inactive due to loss of the invariant catalytic Asp residue. Although the biological role(s) of vertebrate PSKH2s remains unclear, we previously identified species-level adaptions in PSKH2 that have led to the appearance of kinase or pseudokinase variants in vertebrate genomes alongside a canonical PSKH1 paralog. In this paper we confirm that, as predicted, PSKH2 lacks detectable protein phosphotransferase activity, and exploit structural informatics, biochemistry and cellular proteomics to begin to characterise vertebrate PSKH2 orthologues. AlphaFold 2-based structural analysis predicts functional roles for both the PSKH2 N- and C-regions that flank the pseudokinase domain core, and cellular truncation analysis confirms that the N-terminal domain, which contains a conserved myristoylation site, is required for both stable human PSKH2 expression and localisation to a membrane-rich subcellular fraction containing mitochondrial proteins. Using mass spectrometry-based proteomics, we confirm that human PSKH2 is part of a cellular mitochondrial protein network, and that its expression is regulated through client-status within the HSP90/Cdc37 molecular chaperone system. HSP90 interactions are mediated through binding to the PSKH2 C-terminal tail, leading us to predict that this region might act as both a cis and trans regulatory element, driving outputs linked to the PSKH2 pseudokinase domain that are important for functional signalling.

biochemistry↗

bioRxiv2022

Post-Cyclase Skeletal Rearrangements in Plant Triterpenoid Biosynthesis by a Pair of Branchpoint Isomerases

Triterpenoids possess potent biological activities, but their polycyclic skeletons are challenging to synthesise. In biochemistry, the skeletal diversity of plant triterpenoids is normally generated by oxidosqualene cyclases and remains unaltered during subsequent tailoring steps. In contrast, we report here enzyme-mediated skeletal rearrangements after the initial cyclisation, controlling the pathway bifurcation between different plant triterpenoid classes. Using a combination of bioinformatics, heterologous expression in plants and chemical analyses, we identified a cytochrome P450 monooxygenase and two isomerases for this process. The two isomerases share one epoxide substrate but generate two different rearrangement products, one containing a cyclopropane ring. Our findings reveal a new strategy how triterpenoid skeletal diversity is generated in Nature and are crucial for the biotechnological production of limonoid, quassinoid, isoprotolimonoid and glabretane triterpenoids.

biochemistry↗

bioRxiv2022

A conserved and tunable mechanism for the temperature-controlled condensation of the translation factor Ded1p

Heat shock promotes the assembly of translation factors into condensates to facilitate the production of stress-protective proteins. How translation factors detect heat and assemble into condensates is not well understood. Here, we investigate heat-induced condensate assembly by the translation factor Ded1p from five different fungi, including Ded1p from Saccharomyces cerevisiae. Using targeted mutagenesis and in vitro reconstitution biochemistry, we find that heat-induced Ded1p assembly is driven by a conformational rearrangement of the folded helicase domain. This rearrangement determines the assembly temperature and the assembly of Ded1p into nanometer-sized particles, while the flanking intrinsically disordered regions engage in intermolecular interactions to promote assembly into micron-sized condensates. Using protein engineering, we identify six amino acid substitutions that determine most of the thermostability of a thermophilic Ded1p ortholog, thereby providing a molecular understanding underlying the adaptation of the Ded1p assembly temperature to the specific growth temperature of the species. We conclude that heat-induced assembly of Ded1p into translation factor condensates is regulated by a complex interplay of the structured domain and intrinsically disordered regions which is subject to evolutionary tuning.

biochemistry↗

bioRxiv2022

The rugged DNA-binding sequence-fitness landscape of the LacI/GalR Family is a product of asymmetry in the operator:repressor complex

How a proteins function influences the shape of its fitness landscape, smooth or rugged, is a fundamental question in evolutionary biochemistry. Smooth landscapes arise when incremental mutational steps lead to a progressive change in function, as commonly seen in enzymes and binding proteins. On the other hand, rugged landscapes are poorly understood because of the inherent unpredictability of how sequence changes affect function. Here, we experimentally characterize the entire sequence phylogeny, comprising 1158 extant and ancestral sequences, of the DNA-binding domain (DBD) of the LacI/GalR transcriptional repressor family. Our analysis revealed an extremely rugged landscape with rapid switching of specificity even between adjacent nodes. Further, the ruggedness arises due to the necessity of the repressor to simultaneously evolve specificity for asymmetric operators and disfavors potentially adverse regulatory crosstalk. Our study provides fundamental insight into evolutionary, molecular, and biophysical rules of genetic regulation through the lens of fitness landscapes.

biochemistry↗

bioRxiv2022

How do Vampires Suck Blood?

Lampreys are blood-sucking vampires in the marine. From a survival perspective, it is expected that lamprey buccal gland exhibits a repository of pharmacologically active components to modulate the hosts homeostasis, inflammatory and immune responses. Several proteins have been found to function as anticoagulants, ion channel blockers, and immune suppressors in lampreys, while small metabolites have never been explored in detail. In this study, by analyzing the metabolic profiles of 14 different lamprey tissues, we have identified two groups of blood-sucking-associated metabolites, i.e., kynurenine pathway metabolites and prostaglandins, in the buccal gland and they can be injected into the host fish to ensure a steady and sustained blood flow to the feeding site. These findings demonstrate the complex nature of lamprey buccal gland and highlight the diversity in the mechanisms utilized for blood-sucking in lampreys. In addition, a lamprey spatial metabolomics database (https://www.lampreydb.com) was constructed to assist studies using lampreys as model animal. The database contains detailed qualitative, quantitative, and spatial distribution information of each detected metabolite, and users can easily query and check their metabolites of interest, and/or identify unknown peaks using the database. Significance StatementLampreys are one of the two surviving jawless vertebrate groups that hold the key to our understanding of the early vertebrate evolution, adaptive immune origin, and developmental neurobiology. Here, we applied a spatial metabolomics approach to study the lamprey-host interaction. Two groups of metabolites, i.e., kynurenine pathway metabolites and prostaglandins, were found in the lamprey buccal gland, which modulate the hosts homeostasis, inflammatory and immune responses. The establishment of the first tissue-wide spatial lamprey metabolomics database in this study facilitate future studies in biochemistry, clinical chemistry, natural product discovery, medicine, and metabolomics using lampreys as a model animal.

biochemistry↗

bioRxiv2022

Tropomyosin Cdc8 acetylation enhances binding to expressed S. pombe actin but does not promote differential association with fission yeast formins

It was proposed from cellular studies that S. pombe tropomyosin Cdc8 (Tpm) segregates into two populations due to the presence or absence of an amino-terminal acetylation that specifies which formin-mediated F-actin networks it binds, but with no supporting biochemistry. To address this mechanism in vitro, we developed methods for S. pombe actin expression in Sf9 cells. We then employed 3-color TIRF microscopy using all recombinant S. pombe proteins to probe in vitro multicomponent mechanisms involving actin, acetylated and unacetylated Tpm, formins, and myosins. Acetyl-Tpm exhibits tight binding to actin in contrast to weaker binding by unacetylated Tpm. In disagreement with the differential recruitment model, Tpm showed no preferential binding to filaments assembled by the FH1-FH2-domains of two S. pombe formins, nor did Tpm binding have any bias towards the growing formin-bound actin filament barbed end. Although our in vitro findings do not support a direct formin-tropomyosin interaction, it is possible that formins bias differential tropomyosin isoform recruitment through undiscovered mechanisms. Importantly, despite a 12% sequence divergence between skeletal and S. pombe actin, S. pombe myosins Myo2 and Myo51 exhibited similar motile behavior with these two actins, validating key prior findings with these myosins that used skeletal actin.

biochemistry↗

bioRxiv2022

SARS-CoV-2 Spike Protein Induces Hemagglutination: Implications for COVID-19 Morbidities and Therapeutics and for Vaccine Adverse Effects

Experimental findings for SARS-CoV-2 related to the glycan biochemistry of coronaviruses indicate that attachments from spike protein to glycoconjugates on the surfaces of red blood cells (RBCs), other blood cells and endothelial cells are key to the infectivity and morbidity of COVID-19. To provide further insight into these glycan attachments and their potential clinical relevance, the classic hemagglutination (HA) assay was applied using spike protein from the Wuhan, Alpha, Delta and Omicron B.1.1.529 lineages of SARS-CoV-2 mixed with human RBCs. The electrostatic potential of the central region of spike protein from these four lineages was studied through molecular modeling simulations. Inhibition of spike protein-induced HA was tested using the macrocyclic lactone ivermectin (IVM), which is indicated to bind strongly to SARS-CoV-2 spike protein glycan sites. The results of these experiments were, first, that spike protein from these four lineages of SARS-CoV-2 induced HA. Omicron induced HA at a significantly lower threshold concentration of spike protein than for the three prior lineages and was much more electropositive on its central spike protein region. IVM blocked HA when added to RBCs prior to spike protein and reversed HA when added afterwards. These results validate and extend prior findings on the role of glycan bindings of viral spike protein in COVID-19. They furthermore suggest therapeutic options using competitive glycan-binding agents such as IVM and may help elucidate rare serious adverse effects (AEs) associated with COVID-19 mRNA vaccines which use spike protein as the generated antigen.

biochemistry↗

bioRxiv2022

Targeted Kinase Degradation via the KLHDC2 Ubiquitin E3 Ligase

Chemically induced protein degradation is a powerful strategy for perturbing cellular biochemistry. The predominant mechanism of action for protein degrader drugs involves induced proximity between the cellular ubiquitin conjugation machinery and the target. Unlike traditional small molecule enzyme inhibition, targeted protein degradation can clear an undesired protein from cells. We demonstrate here the use of peptide ligands for Kelch-Like Homology Domain Containing protein 2 (KLHDC2), a substrate adaptor protein and member of the cullin-2 (CUL2) ubiquitin ligase complex, for targeted protein degradation. Peptide-based bivalent compounds that can induce proximity between KLHDC2 and target proteins cause degradation of the targeted factors. The cellular activity of these compounds depends on KLHDC2 binding. This work demonstrates the utility of KLHDC2 for targeted protein degradation and exemplifies a strategy for the rational design of new peptide-based ligands useful for this purpose.

biochemistry↗

bioRxiv2023

Ndel1 modulates dynein activation in two distinct ways

Dynein is the primary minus-end-directed microtubule motor [1]. To achieve activation, dynein binds to the dynactin complex and an adaptor to form the "activated dynein complex" [2, 3]. The protein Lis1 aids activation by binding to dynein and promoting its association with dynactin and adaptor [4, 5]. Ndel1 and its orthologue Nde1 are dynein and Lis1 binding proteins that help control where dynein localizes within the cell [6]. Cell-based assays suggest that Ndel1/Nde1 also work with Lis1 to promote dynein activation, although the underlying mechanism is unclear [6]. Using purified proteins and quantitative binding assays, we found that Ndel1s C-terminal region contributes to binding to dynein and negatively regulates binding to Lis1. Using single-molecule imaging and protein biochemistry, we observed that Ndel1 inhibits dynein activation in two distinct ways. First, Ndel1 disfavors the formation of the activated dynein complex. We found that phosphomimetic mutations in Ndel1s C-terminal domain increase its ability to inhibit dynein-dynactin-adaptor complex formation. Second, we observed that Ndel1 interacts with dynein and Lis1 simultaneously and sequesters Lis1 away from its dynein binding site. In doing this, Ndel1 prevents Lis1-mediated dynein activation. Our work suggests that in vitro, Ndel1 is a negative regulator of dynein activation, which contrasts with cellular studies where Ndel1 promotes dynein activity. To reconcile our findings with previous work, we posit that Ndel1 functions to scaffold dynein and Lis1 together while keeping dynein in an inhibited state. We speculate that Ndel1 release can be triggered in cellular settings to allow for timed dynein activation.

biochemistry↗