Project description:SARS-CoV-2 nsp7 and nsp8 are important cofactors of the RTC, as they interact and regulate the activity of RNA-dependent RNA polymerase and other nspsHere we used solution-based structural proteomic techniques, hydrogen-deuterium exchange mass spectrometry (HDX-MS) and crosslinking mass spectrometry (XL-MS), illuminate the dynamics of SARS-CoV-2 full-length nsp7, nsp8, and nsp7:nsp8 proteins and protein complex.
Project description:SARS-CoV-2, a human coronavirus, is the causative agent of the COVID-19 pandemic, entailing enormous disruption worldwide. Its ~30 kb RNA genome is translated into two large polyproteins subsequently cleaved by viral papain-like protease and main protease (Mpro/nsp5). Polyprotein processing is essential yet incompletely understood. We studied Mpro-mediated processing of the nsp7-10/11 polyprotein, whose mature products are cofactors of the viral replicase, identifying the order of cleavages: 1) nsp9-10, 2) nsp8-9/nsp10-11, and 3) nsp7-8. Integrative modeling based on mass spectrometry (including hydrogen-deuterium exchange and cross-linking) and X-ray scattering yielded three-dimensional models of the nsp7-10/11 polyprotein, and the data suggest that the nsp7-10/11 structure in complex with Mpro strongly resembles the unbound polyprotein. Our array of techniques supports the notion that interplay between polyprotein conformation and junction accessibility determine the preference and order of cleavages. Finally, we leveraged assays of limited proteolysis by Mpro of nsp7-11 using a series of inhibitors/binders to characterize Mpro inhibition using a polyprotein substrate.
Project description:In this study, we performed proteome-wide crosslinking mass spectrometry (XLMS) on human HEK293 intact organelles and examined the combined utility of these crosslinks with AlphaFold.
Project description:During co-translational translocation at the endoplasmic reticulum (ER), ribosomes can stall and become covalently modified with the ubiquitin-like protein UFM1 on the 60S ribosomal subunit RPL26 (uL24). This process, known as UFMylation, is mediated by the UFM1 Ribosome E3 Ligase (UREL) complex, comprised of UFL1, UFBP1, and CDK5RAP3. However, the functional consequences of UFMylation and catalytic mechanisms of UREL are unknown. Here, we present crosslinking-mass spectrometry (XL-MS) data of UREL bound to 60S ribosomes.
Project description:Chemical-Crosslinking Mass Spectrometry (XLMS) using MS-cleavable crosslinkers is fast becoming an established technique in the study of protein-protein interactions for both small and large scale samples. With the increased uptake of XLMS as a technique, different combinations of crosslinker types, fragmentation strategies and analysis programs are being applied to a diverse array of biological samples. This study is focused on understanding how the three variables of an XLMS experiment – crosslinker type, fragmentation and program – could generate differences in identifications, leading to increased biological coverage of a sample. Here we probe for the first time, the known enzyme:substrate interaction between yeast arginine methyltransferase Hmt1p and its substrate, heterologous nucleolar protein Npl3p. We use this known interaction as a platform to compare two analysis programs, MeroX and XlinkX2.0, using two crosslinker types, DSSO and DSBU, and two mass-spectrometry fragmentation strategies, CID/ETD and SteppedHCD. Through these we also compare different algorithm strategies, Precursor and Reporter-Ion, as well as assess the impact of restricting data searches to lysine only crosslinks versus the inclusion of serine, threonine and tyrosine as reactive residues. From this analysis we show direct evidence of Hmt1p in contact with its known methylation sites on Npl3p, the intrinsically disordered “SRGG” region. We also show through our multi-crosslinker, multi-fragmentation and multi-software approach that two approaches leads to greater understanding and depth of a crosslinked sample, and this is due to some combinations of experimental variables creating greater coverage of crosslinks than others.
Project description:Studies using crosslinking coupled to mass spectrometry on the proteome-wide level have spurred great interest as they facilitate structural probing of protein interactions in living cells or even organisms. Here we show, by using both an in-vitro mimic of a crowded cellular environment and eukaryotic cell lysates, that current proteome-wide crosslinking protocols have a bias for high abundant proteins. We demonstrate that this bias can be explained by kinetics that govern the formation of a crosslink between two polypeptides. We further show that optimized parameter settings, in particularly an excess of crosslinker, leadto a significant overall increase in the detection of lower abundant proteins within cellular lysates on a proteome-wide scale. Our study therefore explains the cause of a major limitation in current proteome-wide crosslinking studies and demonstrates a way forward how to address a larger part of the proteome by crosslinking
Project description:We have created a synthetic crosslinked peptide library to benchmark crosslinking mass spectrometry search engines. The unique benefit of the library is knowing which identified crosslinks are true and which are false. The data collected from mass spectrometry measurements of the peptide library were used to assess the most frequently used search algorithms. The datasets included will provide an important resource for the crosslinking community to evaluate and optimise search engines, results from which have far-reaching implications.
Project description:We use a combination of multiple structural proteomics techniques (differential photo-reactive surface modification, HDX, crosslinking and epitope excision/extraction) for the determination of the protein antigen epitopes for monoclonal antibodies.
Project description:Guanylate binding proteins (GBP) belong to the superfamily of dynamin proteins. Those might assemble into larger structures upon initial dimerization. We analyzed monomeric and dimerization of mGBP7 via molecular dynamic simulations and compared the developed models with data from crosslinking mass spectrometry experiments.
Project description:As part of an in-depth characterization of nanobodies directed against the Chlorobium tepidum protein CtRoco, a bacterial LRRK2 homologue, chemical crosslinking combined with mass spectrometry (CX-MS) was performed. Two allosteric nanobodies binding to two different epitopes in the LRR and the Roc domain of CtRoco, respectively were analysed using the CID-cleavable crosslinker disuccinimidyl sulfoxide (DSSO).