6 Oct 2022

A broad and potent neutralization epitope in SARS-related coronaviruses (PNAS)

Since the beginning of the COVID-19 pandemic, many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have emerged that are resistant to varying extents to neutralizing antibody responses induced by current vaccines and natural infection, especially the recent Omicron variants. Neutralizing potency and breadth for an antibody are often somewhat mutually exclusive. Here, we delineate the molecular interaction between a therapeutic antibody (ADG20) and SARS-CoV-2 receptor-binding domain (RBD) by X-ray crystallography and characterize its binding epitope. We show that this site is targeted by a few rare antibodies that have both potency and breadth. These findings provide insights into the design of more universal vaccines and broad therapeutic antibodies, which are pressingly needed.

6 Oct 2022

SARS-CoV-2 Delta and Omicron variants evade population antibody response by mutations in a single spike epitope (Nature Microbiology)

Population antibody response is thought to be important in selection of virus variants. We report that SARS-CoV-2 infection elicits a population immune response that is mediated by a lineage of VH1-69 germline antibodies. A representative antibody R1-32 from this lineage was isolated. By cryo-EM, we show that it targets a semi-cryptic epitope in the spike receptor-binding domain. Binding to this non-ACE2 competing epitope results in spike destruction, thereby inhibiting virus entry. On the basis of epitope location, neutralization mechanism and analysis of antibody binding to spike variants, we propose that recurrent substitutions at 452 and 490 are associated with immune evasion of the identified population antibody response. These substitutions, including L452R (present in the Delta variant), disrupt interactions mediated by the VH1-69-specific hydrophobic HCDR2 to impair antibody-antigen association, enabling variants to escape. The first Omicron variants were sensitive to antibody R1-32 but subvariants that harbour L452R quickly emerged and spread. Our results provide insights into how SARS-CoV-2 variants emerge and evade host immune responses.

6 Oct 2022

Posttranslational modifications optimize the ability of SARS-CoV-2 spike for effective interaction with host cell receptors (PNAS)

SARS-CoV-2 spike protein, which forms the basis for high pathogenicity and transmissibility of the virus, is a prime target for the development of both diagnostics and vaccines for the debilitating disease caused by the virus. We present a full model of spike methodically crafted and used to study its atomic-level dynamics by multiple microsecond simulations. The results shed light on the impact of posttranslational modifications on the pathogenicity of the virus. We show how glycan–glycan and glycan–lipid interactions broaden the protein’s dynamical range and thereby, its effective interaction with the surface receptors on the host cell. Palmitoylation of the spike membrane domain, however, results in a unique deformation pattern that might prime the membrane for fusion.

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.

21 Nov 2023

Intrinsic structural dynamics dictate enzymatic activity and inhibition (PNAS)

Enzymes are known to sample various conformations, many of which are critical for their biological function. However, structural characterizations of enzymes predominantly focus on the most populated conformation. As a result, single-point mutations often produce structures that are similar or essentially identical to those of the wild-type enzyme despite large changes in enzymatic activity. Here, we show for mutants of a histone deacetylase enzyme (HDAC8) that reduced enzymatic activities, reduced inhibitor affinities, and reduced residence times are all captured by the rate constants between intrinsically sampled conformations that, in turn, can be obtained independently by solution NMR spectroscopy. Thus, for the HDAC8 enzyme, the dynamic sampling of conformations dictates both enzymatic activity and inhibitor potency. Our analysis also dissects the functional role of the conformations sampled, where specific conformations distinct from those in available structures are responsible for substrate and inhibitor binding, catalysis, and product dissociation. Precise structures alone often do not adequately explain the effect of missense mutations on enzymatic activity and drug potency. Our findings not only assign functional roles to several conformational states of HDAC8 but they also underscore the paramount role of dynamics, which will have general implications for characterizing missense mutations and designing inhibitors.

21 Nov 2023

Streamlined structure determination by cryo-electron tomography and subtomogram averaging using TomoBEAR (Nature Communications)

Structures of macromolecules in their native state provide unique unambiguous insights into their functions. Cryo-electron tomography combined with subtomogram averaging demonstrated the power to solve such structures in situ at resolutions in the range of 3 Angstrom for some macromolecules. In order to be applicable to the structural determination of the majority of macromolecules observable in cells in limited amounts, processing of tomographic data has to be performed in a high-throughput manner. Here we present TomoBEAR—a modular configurable workflow engine for streamlined processing of cryo-electron tomographic data for subtomogram averaging. TomoBEAR combines commonly used cryo-EM packages with reasonable presets to provide a transparent (“white box”) approach for data management and processing. We demonstrate applications of TomoBEAR to two data sets of purified macromolecular targets, to an ion channel RyR1 in a membrane, and the tomograms of plasma FIB-milled lamellae and demonstrate the ability to produce high-resolution structures. TomoBEAR speeds up data processing, minimizes human interventions, and will help accelerate the adoption of in situ structural biology by cryo-ET. The source code and the documentation are freely available.

21 Nov 2023

Editorial Overview: Protein-nucleic Acid Interactions (Current Opinion in Structural Biology)

Protein-nucleic interactions play crucial roles in a wide range of processes, ranging from the expression, proliferation, and preservation of genetic information to immuno-sensing and advances in disease treatment. Understanding the structural basis of these interactions is essential for deciphering the molecular mechanisms underlying these fundamental processes and providing a foundation for biotechnological and therapeutic discovery. In this section of Current Opinion in Structural Biology, we present a collection of recent breakthroughs in the field of protein-nucleic interactions, showcasing the latest advancements in our understanding of the structural and biophysical principles governing their formation and function.

21 Nov 2023

Digital quantum simulations of NMR experiments (Science)

Simulations of nuclear magnetic resonance (NMR) experiments can be an important tool for extracting information about molecular structure and optimizing experimental protocols but are often intractable on classical computers for large molecules such as proteins and for protocols such as zero-field NMR. We demonstrate the first quantum simulation of an NMR spectrum, computing the zero-field spectrum of the methyl group of acetonitrile using four qubits of a trapped-ion quantum computer. We reduce the sampling cost of the quantum simulation by an order of magnitude using compressed sensing techniques. We show how the intrinsic decoherence of NMR systems may enable the zero-field simulation of classically hard molecules on relatively near-term quantum hardware and discuss how the experimentally demonstrated quantum algorithm can be used to efficiently simulate scientifically and technologically relevant solid-state NMR experiments on more mature devices. Our work opens a practical application for quantum computation.

31 Oct 2023

Molecular basis of RNA-binding and autoregulation by the cancer-associated splicing factor RBM39 (Nature Communications)

Pharmacologic depletion of RNA-binding motif 39 (RBM39) using aryl sulfonamides represents a promising anti-cancer therapy but requires high levels of the adaptor protein DCAF15. Consequently, novel approaches to deplete RBM39 in an DCAF15-independent manner are required. Here, we uncover that RBM39 autoregulates via the inclusion of a poison exon into its own pre-mRNA and identify the cis-acting elements that govern this regulation. We also determine the NMR solution structures of RBM39’s tandem RNA recognition motifs (RRM1 and RRM2) bound to their respective RNA targets, revealing how RRM1 recognises RNA stem loops whereas RRM2 binds specifically to single-stranded N(G/U)NUUUG. Our results support a model where RRM2 selects the 3’-splice site of a poison exon and the RRM3 and RS domain stabilise the U2 snRNP at the branchpoint. Our work provides molecular insights into RBM39-dependent 3’-splice site selection and constitutes a solid basis to design alternative anti-cancer therapies.