On the role of nucleotides and lipids in the polymerization of the actin homolog MreB from a Gram-positive bacterium
- Micalis Institute, France
- Leibniz Institute of Polymer Research, Germany
- CNRS Université Paris-Saclay, France
- Institut Curie, France
Abstract
In vivo, bacterial actin MreB assembles into dynamic membrane-associated filamentous structures that exhibit circumferential motion around the cell. Current knowledge of MreB biochemical and polymerization properties in vitro remains limited and is mostly based on MreB proteins from Gram-negative species. In this study, we report the first observation of organized protofilaments by electron microscopy and the first 3D-structure of MreB from a Gram-positive bacterium. We show that Geobacillus stearothermophilus MreB forms straight pairs of protofilaments on lipid surfaces in the presence of ATP or GTP, but not in the presence of ADP, GDP or non-hydrolysable ATP analogs. We demonstrate that membrane anchoring is mediated by two spatially close short hydrophobic sequences while electrostatic interactions also contribute to lipid binding, and show that the population of membrane-bound protofilament doublets is in steady-state. In solution, protofilament doublets were not detected in any condition tested. Instead, MreB formed large sheets regardless of the bound nucleotide, albeit at a higher critical concentration. Altogether, our results indicate that both lipids and ATP are facilitators of MreB polymerization, and are consistent with a dual effect of ATP hydrolysis, in promoting both membrane binding and filaments assembly/disassembly.
Data availability
Protein structures data have been deposited in PDB under the accession codes 7ZPT and 8AZG.
Article and author information
Author details
Ines Li de la Sierra-Gallay
Rut Carballido-Lopez
Funding
European Research Council (ERC-SG,311231)
- Rut Carballido-Lopez
European Research Council (ERC-CG,772178)
- Rut Carballido-Lopez
Agence Nationale de la Recherche (ANR-11-LABX0038)
- Aurélie Bertin
Agence Nationale de la Recherche (ANR-10-IDEX-0001-02)
- Aurélie Bertin
VolkswagenStiftung
- Lars D Renner
Agence Nationale de la Recherche (ANR-10-INSB-05-05)
- Sylvie Nessler
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Mao 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.
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