Structure of the two-component S-layer of the archaeon Sulfolobus acidocaldarius
Abstract
Surface layers (S-layers) are resilient two-dimensional protein lattices that encapsulate many bacteria and most archaea. In archaea, S-layers usually form the only structural component of the cell wall and thus act as the final frontier between the cell and its environment. Therefore, S-layers are crucial for supporting microbial life. Notwithstanding their importance, little is known about archaeal S-layers at the atomic level. Here, we combined single particle cryo electron microscopy (cryoEM), cryo electron tomography (cryoET) and Alphafold2 predictions to generate an atomic model of the two-component S-layer of Sulfolobus acidocaldarius. The outer component of this S-layer (SlaA) is a flexible, highly glycosylated, and stable protein. Together with the inner and membrane-bound component (SlaB), they assemble into a porous and interwoven lattice. We hypothesise that jackknife-like conformational changes, changes play important roles in S-layer assembly.
Data availability
The atomic coordinates of SlaA were deposited in the Protein Data Bank (https://www.rcsb.org/) with accession numbers PDB-7ZCX, PDDB-8AN3, and PDB-8AN3 for pH 4, 7 and 10, respectively. The electron density maps were deposited in the EM DataResource (https://www.emdataresource.org/) with accession numbers EMD-14635, EMD-15531 and EMD-15531 for pH 4, 7 and 10, respectively.Sub-tomogram averaging map of the S-layer has been deposited in the EMDB (EMD-18127) and models of the hexameric and trimeric pores in the Protein Databank under accession codes PDB-8QP0 and PDB-8QOX, respectivelyOther structural data used in this study are: H. volcanii csg (PDB ID: 7PTR, http://dx.doi.org/10.2210/pdb7ptr/pdb), and C. crescentus RsaA ((N-terminus PDB ID: 6T72, http://dx.doi.org/10.2210/pdb6t72/pdb, C-terminus PDB ID: 5N8P, http://dx.doi.org/10.2210/pdb5n8p/pdb).
Article and author information
Author details
Funding
European Research Council (803894)
- Lavinia Gambelli
- Mathew McLaren
- Rebecca Conners
- Kelly Sanders
- Matthew C Gaines
- Bertram Daum
Wellcome Trust (210363/Z/18/Z)
- Rebecca Conners
- Vicki AM Gold
Wellcome Trust (212439/Z/18/Z)
- Bertram Daum
Agence Nationale de la Recherche (ANR-16-CE16-0009-01)
- Cyril Hanus
Agence Nationale de la Recherche (ANR-21-CE16-0021-01)
- Cyril Hanus
Leverhulme Trust (RPG-2020-261)
- Daniel Kattnig
Biotechnology and Biological Sciences Research Council (BB/R008639/1)
- Rebecca Conners
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Han Remaut, VIB-VUB Center for Structural Biology, Belgium
Version history
- Preprint posted: October 7, 2022 (view preprint)
- Received: November 1, 2022
- Accepted: January 19, 2024
- Accepted Manuscript published: January 22, 2024 (version 1)
- Version of Record published: February 29, 2024 (version 2)
Copyright
© 2024, Gambelli et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 887
- views
-
- 202
- downloads
-
- 3
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Biochemistry and Chemical Biology
- Structural Biology and Molecular Biophysics
Invertebrates use the endoribonuclease Dicer to cleave viral dsRNA during antiviral defense, while vertebrates use RIG-I-like Receptors (RLRs), which bind viral dsRNA to trigger an interferon response. While some invertebrate Dicers act alone during antiviral defense, Caenorhabditis elegans Dicer acts in a complex with a dsRNA binding protein called RDE-4, and an RLR ortholog called DRH-1. We used biochemical and structural techniques to provide mechanistic insight into how these proteins function together. We found RDE-4 is important for ATP-independent and ATP-dependent cleavage reactions, while helicase domains of both DCR-1 and DRH-1 contribute to ATP-dependent cleavage. DRH-1 plays the dominant role in ATP hydrolysis, and like mammalian RLRs, has an N-terminal domain that functions in autoinhibition. A cryo-EM structure indicates DRH-1 interacts with DCR-1’s helicase domain, suggesting this interaction relieves autoinhibition. Our study unravels the mechanistic basis of the collaboration between two helicases from typically distinct innate immune defense pathways.
-
- Biochemistry and Chemical Biology
- Structural Biology and Molecular Biophysics
The type II class of RAF inhibitors currently in clinical trials paradoxically activate BRAF at subsaturating concentrations. Activation is mediated by induction of BRAF dimers, but why activation rather than inhibition occurs remains unclear. Using biophysical methods tracking BRAF dimerization and conformation, we built an allosteric model of inhibitor-induced dimerization that resolves the allosteric contributions of inhibitor binding to the two active sites of the dimer, revealing key differences between type I and type II RAF inhibitors. For type II inhibitors the allosteric coupling between inhibitor binding and BRAF dimerization is distributed asymmetrically across the two dimer binding sites, with binding to the first site dominating the allostery. This asymmetry results in efficient and selective induction of dimers with one inhibited and one catalytically active subunit. Our allosteric models quantitatively account for paradoxical activation data measured for 11 RAF inhibitors. Unlike type II inhibitors, type I inhibitors lack allosteric asymmetry and do not activate BRAF homodimers. Finally, NMR data reveal that BRAF homodimers are dynamically asymmetric with only one of the subunits locked in the active αC-in state. This provides a structural mechanism for how binding of only a single αC-in inhibitor molecule can induce potent BRAF dimerization and activation.