Biology subjects

Salzer, R.

Publications and source records attributed to Salzer, R..

4 recordsLinked to original sources

bioRxiv2025

Molecular structure of the ESCRT III-based archaeal CdvAB cell division machinery

Most prokaryotes divide using filaments of the tubulin-like FtsZ protein, while some archaea employ instead ESCRT-III-like proteins and their filaments for cell division and cytokinesis. The alternative archaeal system comprises Cdv proteins and is thought to bear some resemblance to ESCRT-III-based membrane remodelling in other domains of life, including eukaryotes, especially during abscission. Here we present biochemical, crystallographic and cryo-EM studies of the Sulfolobus Cdv machinery. CdvA, an early non-ESCRT component, adopts a PRC-domain/coiled-coil fold and polymerises into long double-stranded helical filaments, mainly via hydrophobic interfaces. Monomeric CdvB adopts the canonical ESCRT-III fold in both a closed and a distinct "semi-open" conformation. Soluble CdvB2 filaments are composed of subunits in the closed state, appearing to transition to the open, active state only when polymerised on membranes. Short N-terminal amphipathic helices in all CdvB paralogues, B, B1 and B2, mediate membrane binding and are required for liposome recruitment in vitro. We provide a molecular overview of archaeal ESCRT-III-based cytokinesis machinery, the definitive demonstration that CdvB proteins are bona fide ESCRT-III homologues and we reveal the molecular basis for membrane engagement. Thus, we illuminate conserved principles of ESCRT-mediated membrane remodelling and extend them to an anciently diverged archaeal lineage. Significance statementMembrane remodelling by ESCRT-III proteins is a fundamental and conserved process across the tree of life. The archaeal ESCRT-III-based cell division system (Cdv) drives cytokinesis in many archaeal groups, yet the molecular architecture of its components remained unknown, making it difficult to decipher the molecular mechanisms employed for cell division and cytokinesis in these organisms. We present structures of the Cdv machinery in Sulfolobus organisms that have been used previously to study the cell division process. We show that CdvA forms unexpected antiparallel helical filaments, while the ESCRT-III homologues retain the canonical fold we show they share with eukaryotic proteins. We demonstrate that N-terminal helices mediate membrane binding and that membrane contact, rather than polymerisation alone, likely triggers activation of Cdv ESCRT-IIIs.

molecular biology↗

bioRxiv2021

Characterisation of the Ubiquitin-ESCRT pathway in Asgard archaea sheds new light on origins of membrane trafficking in eukaryotes

The ESCRT machinery performs a critical role in membrane remodelling events in all eukaryotic cells, including in membrane trafficking, membrane repair, cytokinetic abscission, in viral egress, and in the generation of extracellular vesicles. While the machinery is complex in modern day eukaryotes, where it comprises dozens of proteins, the system has simpler and more ancient origins. Indeed, homologues of ESCRT-III and the Vps4 ATPase, the proteins that execute the final membrane scission reaction, play analogous roles in cytokinesis and potentially in extracellular vesicle formation in TACK archaea where ESCRT-I and II homologues seem to be absent. Here, we explore the phylogeny, structure, and biochemistry of homologues of the ESCRT machinery and the associated ubiquitylation system found in genome assemblies of the recently discovered Asgard archaea. In these closest living prokaryotic relatives of eukaryotes, we provide evidence for the ESCRT-I and II sub-complexes being involved in the ubiquitin-directed recruitment of ESCRT-III,_as it is in eukaryotes. This analysis suggests a pre-eukaryotic origin for the Ub-coupled ESCRT system and a likely path of ESCRT evolution via a series of gene duplication and diversification events.

cell biology↗

bioRxiv2021

Single-dose immunisation with a multimerised SARS-CoV-2 receptor binding domain (RBD) induces an enhanced and protective response in mice

The COVID-19 pandemic, caused by the SARS-CoV-2 coronavirus, has triggered a worldwide health emergency. So far, several different types of vaccines have shown strong efficacy. However, both the emergence of new SARS-CoV-2 variants and the need to vaccinate a large fraction of the worlds population necessitate the development of alternative vaccines, especially those that are simple and easy to store, transport and administer. Here, we showed that ferritin-like Dps protein from hyperthermophilic Sulfolobus islandicus can be covalently coupled with different SARS-CoV-2 antigens via the SpyCatcher system, to form extremely stable and defined multivalent dodecameric vaccine nanoparticles that remain intact even after lyophilisation. Immunisation experiments in mice demonstrated that the SARS-CoV-2 receptor binding domain (RBD) coupled to Dps (RBD-S-Dps) shows particular promise as it elicited a higher antibody titre and an enhanced neutralising antibody response compared to the monomeric RBD. Furthermore, we showed that a single immunisation with the multivalent RBD-S-Dps completely protected hACE2-expressing mice from serious illness and led to efficient viral clearance from the lungs upon SARS-CoV-2 infection. Our data highlight that multimerised SARS-CoV-2 subunit vaccines are a highly efficacious modality, particularly when combined with an ultra-stable scaffold.

immunology↗

bioRxiv2019

A new twist on bacterial motility - Two distinct type IV pili revealed by cryoEM

Many bacteria express flexible protein filaments on their surface that enable a variety of important cellular functions. Type IV pili are examples of such filaments and are comprised of a helical assembly of repeating pilin subunits. Type IV pili are involved in motility (twitching), surface adhesion, biofilm formation and DNA uptake (natural transformation). They are therefore powerful structures that enable bacterial proliferation and genetic adaptation, potentially leading to the development of pathogenicity and antibiotic resistance. They are also targets for drug development.\n\nBy a complement of experimental approaches, we show that the bacterium Thermus thermophilus produces two different forms of type IV pilus. We have determined the structures of both and built atomic models. The structures answer key unresolved questions regarding the molecular architecture of type IV pili and identify a new type of pilin. We also delineate the roles of the two filaments in promoting twitching and natural transformation.

biophysics↗