Czech National Centre of the European Research Infrastructure Consortium INSTRUCT ERIC

26 Nov

Structural ubiquitin contributes to K48 linkage-specificity of the HECT ligase Tom1

Homologous to E6AP C-Terminus (HECT) ubiquitin ligases play key roles in essential pathways such as DNA repair, cell cycle control or protein quality control. Tom1 is one of five HECT ubiquitin E3 ligases encoded in the S. cerevisiae genome and prototypical for a ligase with pleiotropic functions such as ubiquitin chain amplification, orphan quality control and DNA damage response. Structures of full-length HECT ligases, including the Tom1 ortholog HUWE1, have been reported, but how domains beyond the conserved catalytic module contribute to catalysis remains largely elusive. Here, through cryogenic electron microscopy (cryo-EM) of Tom1 during an active ubiquitylation cycle, we demonstrate that the extended domain architecture directly contributes to activity. We identify a Tom1-ubiquitin architecture during ubiquitylation involving a non-canonical ubiquitin binding site in the solenoid shape of Tom1. We demonstrate that this ubiquitin binding site coordinates a structural ubiquitin contributing to the fidelity of K48 poly-ubiquitin chain assembly.​

26 Nov

Large-Scale Quantitative Cross-Linking and Mass Spectrometry Provides New Insight on Protein Conformational Plasticity within Organelles, Cells, and Tissues (Biorxiv)

Many proteins can exist in multiple conformational states in vivo to achieve distinct functional roles. These states include alternative conformations, variable PTMs, and association with interacting protein, nucleotide, and ligand partners. Quantitative chemical cross-linking of live cells, organelles, or tissues together with mass spectrometry provides the relative abundance of cross-link levels formed in two or more compared samples, which depends both on the relative levels of existent protein conformational states in the compared samples as well as the relative likelihood of the cross-link originating from each. Because cross-link conformational state preferences can vary widely, one expects intra-protein cross-link levels from proteins with high conformational plasticity to display divergent quantitation among samples with differing conformational ensembles. Here we use the large volume of quantitative cross-linking data available on the public XLinkDB database to cluster intra-protein cross-links according to their quantitation in many diverse compared samples to provide the first widescale glimpse of cross-links grouped according to the protein conformational state(s) from which they predominantly originate. We further demonstrate how cluster cross-links can be aligned with any protein structure to assess the likelihood that they were derived from it.​

25 Nov

Improved automated model building for cryo-EM maps using CryFold (Biorxiv)

Constructing atomic models from cryogenic electron microscopy (cryo-EM) density maps is essential for interpreting molecular mechanisms. In this study, we present CryFold, an approach for de novo model building in cryo-EM that leverages recent advancements in AlphaFold2 to improve the state-of-the-art method ModelAngelo. To incorporate the cryo-EM map information, CryFold replaces the global attention mechanism in AlphaFold2 to local attention, further enhanced by a novel 3D rotary position embedding. It produces more complete models, accelerates the modeling, and reduces the resolution requirement. Applying CryFold to new maps results in accurate differentiation between paralog sequences in noisy regions, detection of previously uncharacterized proteins with unknown functions, precise compartmentalisation of the map for isolation of non-protein components, and improved modeling of conformational changes. In a particular case, a 104-protein complex was modeled within only 5.6 hours, and a minor conformational change of a single protein domain was detected at the periphery when models from two different maps were compared. CryFold stands as an accurate method currently available for model building of proteins in cryo-EM structure determination. CryFold is open-source software available at https://github.com/SBQ-1999/CryFold.​

7 Dec 2023

Celebrating 30 years of Structure

Journal Structure was launched in 1993 as the first journal exclusively dedicated to structural biology by our founding academic chief editors, Wayne A. Hendrickson and Carl-Ivar Br€ande´ n, who were later joined by Alan Fersht. Christopher Lima and Andrej Sali became academic chief editors of Structure in 2003, and they were at the helm of the journal for 18 years until stepping down in the autumn 2021.

Structure is now celebrating its 30th birthday with this special anniversary issue. Editors commissioned reviews to highlight recent developments in different areas of structural biology. Sabine Botha and Petra Fromme provide an overview of the current state of serial femtosecond crystallography (SFX) research, the impact COVID-19 had on the SFX community, and how scientists adapted to these challenges. Koji Yonekura and his co-workers describe their contributions toward the development of electron 3D crystallography/microcrystal electron diffraction (MicroED) and highlight applications and current limitations of this method. Vaibhav KumarShukla, Gabriella Heller, and Flemming Hansen discuss the impact of artificial intelligence (AI) on biomolecular nuclear magnetic resonance (NMR) spectroscopy. Tuo Wang and his colleagues report how solid-state NMR is used to study the structures of fungaland plant cell walls. Syma Khalid and her co-workers define the term ‘‘computational microbiology’’ and describe state-of-the-art molecular dynamics imulations of bacterial systems.

21 Nov 2023

Soft-landing methods aim to simplify structural biology (Nature)

Linking mass spectrometry with cryo-electron microscopy could transform understanding of complex protein structures — if scientists can show that samples remain intact when they hit their target. In his lecture after winning a share of the 2002 Nobel Prize in Chemistry, John Fenn described his work as creating “wings for molecular elephants”. Fenn pioneered the use of a method called electrospray ionization (ESI) to make intact proteins — among nature’s beefiest biomolecules — literally fly, transferring them from complex mixtures into gases and then into mass spectrometers for extensive analysis. Alongside the research of co-recipient Koichi Tanaka, Fenn’s work made it possible for scientists to dive deep into the chemical composition — and therefore the sequences, chemical modifications, and molecular partners — of whole proteins, using mass spectrometry.

21 Nov 2023

Identification of motif-based interactions between SARS-CoV-2 protein domains and human peptide ligands pinpoint antiviral targets (Nature Communications)

The virus life cycle depends on host-virus protein-protein interactions, which often involve a disordered protein region binding to a folded protein domain. Here, we used proteomic peptide phage display (ProP-PD) to identify peptides from the intrinsically disordered regions of the human proteome that bind to folded protein domains encoded by the SARS-CoV-2 genome. Eleven folded domains of SARS-CoV-2 proteins were found to bind 281 peptides from human proteins, and affinities of 31 interactions involving eight SARS-CoV-2 protein domains were determined (K_D ∼ 7-300 μM). Key specificity residues of the peptides were established for six of the interactions. Two of the peptides, binding Nsp9 and Nsp16, respectively, inhibited viral replication. Our findings demonstrate how high-throughput peptide binding screens simultaneously identify potential host-virus interactions and peptides with antiviral properties. Furthermore, the high number of low-affinity interactions suggests that overexpression of viral proteins during infection may perturb multiple cellular pathways.