A deep XL-proteomic dataset of intact HEK293T cells using DSBSO
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ABSTRACT: Cross-linking mass spectrometry is an emerging method to study protein-protein interactions (PPIs) in intact biological systems. Here, we optimized a workflow for gnerating high coverage maps of PPIs using the enrichable cross-linker Azide-A-DSBSO. This created one of the largest to-date XL-MS datasets, enabling structural characterization of thousands of PPIs in their intact subcellular environment.
Project description:Cross-linking mass spectrometry is an increasingly used, powerful technique to study protein-protein interactions or to provide structural information. Due to sub-stochiometric reaction efficiencies, cross-linked peptides are usually low abundant. This results in challenging data evaluation and the need for an effective enrichment. Here we describe an improved, easy to implement, one-step method to enrich azide-tagged, acid-cleavable disuccinimidyl bis-sulfoxide (DSBSO) cross-linked peptides using dibenzocyclooctyne (DBCO) coupled Sepharose������ beads. We probed this method using recombinant Cas9 and E. coli ribosome. For Cas9, the number of detectable cross-links was increased from ~100 before enrichment to 580 cross-links after enrichment. To mimic a cellular lysate, E. coli ribosome was spiked into a tryptic HEK background at a ratio of 1:2 ��������� 1:100. The number of detectable unique cross-links maintained high at ~100. The estimated enrichment efficiency was improved by factor 4 -5 (based on XL numbers) compared to enrichment via biotin and streptavidin. We were still able to detect cross-links from 0.25 ������g cross-linked E. coli ribosome in a background of 100 ������g tryptic HEK peptides, indicating a high enrichment sensitivity. In contrast to conventional enrichment techniques, like SEC, the time needed for preparation and MS measurement is significantly reduced. This robust, fast and selective enrichment method for azide-tagged linkers will contribute to map protein-protein interactions, investigate protein architectures in more depth and help to understand complex biological processes.
Project description:The specific functions of cellular organelles and sub-compartments depend on their protein content, which can be characterized by spatial proteomics approaches. However, many spatial proteomics methods are limited in their ability to resolve organellar sub-compartments, profile multiple sub-compartments in parallel, and/or characterize membrane-associated proteomes. Here, we develop a cross-linking assisted spatial proteomics (CLASP) strategy that addresses these shortcomings. Using human mitochondria as a model system, we show that CLASP can elucidate spatial proteomes of all mitochondrial sub-compartments and provide topological insight into the mitochondrial membrane proteome in a single experiment. Biochemical and imaging-based follow-up studies demonstrate that CLASP allows discovering mitochondria-associated proteins and revising previous protein sub-compartment localization and membrane topology data. This study extends the scope of cross-linking mass spectrometry beyond protein structure and interaction analysis towards spatial proteomics, establishes a method for concomitant profiling of sub-organelle and membrane proteomes, and provides a resource for mitochondrial spatial biology
Project description:This submission includes the complete set of raw data generated from the analytical standard, the concept of which is described in our manuscript "Proteome-Scale Recombinant Standards And A Robust High-Speed Search Engine To Advance Cross-Linking MS-Based Interactomics". In this study, we develop a strategy to generate a well-controlled XL-MS standard by systematically mixing and cross-linking recombinant proteins. The standard can be split into independent datasets, each of which has the MS2-level complexity of a typical proteome-wide XL-MS experiment. This submission includes 5 raw datasets (batches 1-5), each comprising 64 randomly selected human proteins engaging in up to 224 allowed protein-protein interactions per dataset. The data were searched with Scout (v. 1.4.14, https://github.com/diogobor/Scout) and results are reported in mzIdentML 1.2.0 format. For the specific results reported in our original publication, please refer to PXD042173.
Project description:Chemical cross-linking reactions (XL) are an important strategy for studying protein-protein interactions (PPIs), including low abundant sub-complexes, in structural biology. However, choosing XL reagents and conditions is laborious and mostly limited to analysis of protein assemblies that can be resolved using SDS-PAGE. To overcome these limitations, we develop here a denaturing mass photometry (dMP) method for fast, reliable and user-friendly optimization and monitoring of chemical XL reactions. The dMP is a robust 2-step protocol that ensures 95 % of irreversible denaturation within only 5 min. We show that dMP provides accurate mass identification across a broad mass range (30 kDa-5 MDa) along with direct label-free relative quantification of all coexisting XL species (sub-complexes and aggregates). We compare dMP with SDS-PAGE and observe that, unlike the benchmark, dMP is time-efficient (3 min/triplicate), requires significantly less material (20-100x) and affords single molecule sensitivity. To illustrate its utility for routine structural biology applications, we show that dMP affords screening of 20 XL conditions in 1 h, accurately identifying and quantifying all coexisting species. Taken together, we anticipate that dMP will have an impact on ability to structurally characterize more PPIs and macromolecular assemblies, expected final complexes but also sub-complexes that form en route.
Project description:Kinetochores form the link between chromosomes and microtubules of the mitotic spindle. The heterodecameric Dam1 complex (Dam1c) is a major component of the S. cerevisiae outer kinetochore, assembling into 3 MDa-sized microtubule-embracing rings, but how ring assembly is specifically initiated at kinetochores remains to be understood. Here, we describe a molecular pathway that provides local control of ring assembly during the establishment of sister kinetochore bi-orientation. We show that Dam1c and the general microtubule plus-end-associated protein (+TIP) Bim1/EB1 form a stable complex depending on a conserved motif in the Duo1 subunit of Dam1c. EM analyses reveal that Bim1 crosslinks protrusion domains of adjacent Dam1c heterodecamers and promotes the formation of oligomers with defined curvature. Disruption of the Dam1c-Bim1 interaction impairs kinetochore localization of Dam1c in metaphase and delays mitosis. Phosphorylation promotes Dam1c-Bim1 binding by relieving an intramolecular inhibition of the Dam1 C-terminus. In addition, Bim1 recruits Bik1/CLIP-170 to Dam1c and induces formation of full rings even in the absence of microtubules. Our data help to explain how new kinetochore end-on attachments are formed during the process of attachment error correction.
Project description:EndoMAP aims to systematically dissect the human endosomal protein complexes. DHSO/DMTMM cross-linking experiment was performed on freshly prepared endosomal pellets from HEK293 cells to capture protein interactions and structures in purified organelles.
Project description:Biomolecular condensates formed by phase separation offer a confined space where protein-protein interactions (PPIs) facilitate distinct biochemical reactions. As their aberrant behavior is increasingly associated with disease, it is crucial to understand the molecular organization of PPIs within condensates. Using quantitative and time-resolved crosslinkingmass spectrometry we directly and specifically monitor PPIs and protein dynamics of fused in sarcoma (FUS) condensates and identify its RNA recognition motif (RRM) as a key player of condensate-specific PPIs and aging. We find that the chaperone HspB8, but not a disease-associated mutant, prevents FUS aging. The disordered region of HspB8 directs its α-crystallin domain (αCD) into FUS condensates. Here, RRM unfolding drives aggregation but binding of HspB8 via a droplet-specific αCD – RRM interface significantly delays the onset of aging. We propose that chaperones such as HspB8 prevent aberrant phase transitions by stabilizing aggregation prone RNA binding domains in times of cellular stress.
Project description:Reanalysis of a synthetic crosslinked peptide library dataset. The three replicates of the XL-MS experiment with the non-cleavable cross-linker DSS from the dataset published in Beveridge et al., Nature Commun., 2020 (PRIDE project PXD014337) were searched with the XL-MS identification tool OpenPepXL for benchmarking purposes.
Project description:We have developed a new and robust in vivo cross-linking mass spectrometry (XL-MS) that utilizes a multifunctional MS-cleavable cross-linker to enable the efficient capture, enrichment, and identification of in vivo cross-linked peptides at the whole proteome scale.
Project description:Biomolecular condensates formed by phase separation offer a confined space where protein-protein interactions (PPIs) facilitate distinct biochemical reactions. As their aberrant behavior is associated with disease, it is crucial to understand the molecular organization of PPIs within condensates. Using quantitative time-resolved crosslinking mass spectrometry (XL-MS) we directly and specifically monitor PPIs and protein dynamics inside condensates formed by the protein fused in sarcoma (FUS) and identify its folded RNA recognition motif (RRM) as a key player of aberrant molecular aging. We find that the chaperone HspB8, but not a disease-associated mutant, prevents FUS aging. In XL-MS and partitioning experiments we find that the disordered region of HspB8 directs its α-crystallin domain (αCD) into FUS droplets where HspB8 prevents aging via condensate-specific αCD–RRM interactions. We propose that chaperones like HspB8 prevent aberrant phase transitions by stabilizing aggregation prone folded domains inside condensates in times of cellular stress.