Assembly principles of a unique cage formed by hexameric and decameric E. coli proteins
- CNRS, European Molecular Biology Laboratory, France
- University of Toronto, Canada
- CNRS, Université Grenoble Alpes, France
- CEA, CNRS, Université Grenoble Alpes, France
Abstract
A 3.3 MDa macromolecular cage between two E. coli proteins with seemingly incompatible symmetries - the hexameric AAA+ ATPase RavA and the decameric inducible lysine decarboxylase LdcI - is reconstructed by cryo-electron microscopy to 11 Å resolution. Combined with a 7.5 Å resolution reconstruction of the minimal complex between LdcI and the LdcI-binding domain of RavA, and the previously solved crystal structures of the individual components, this work enables to build a reliable pseudoatomic model of this unusual architecture and to identify conformational rearrangements and specific elements essential for complex formation. The design of the cage created via lateral interactions between five RavA rings is unique for the diverse AAA+ ATPase superfamily.
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© 2014, Malet 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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- Physics of Living Systems
Bacterial biofilms are communities of bacteria usually attached to solid strata and often differentiated into complex structures. Communication across biofilms has been shown to involve chemical signaling and, more recently, electrical signaling in Gram-positive biofilms. We report for the first time, community-level synchronized membrane potential dynamics in three-dimensional Escherichia coli biofilms. Two hyperpolarization events are observed in response to light stress. The first requires mechanically sensitive ion channels (MscK, MscL, and MscS) and the second needs the Kch-potassium channel. The channels mediated both local spiking of single E. coli biofilms and long-range coordinated electrical signaling in E. coli biofilms. The electrical phenomena are explained using Hodgkin-Huxley and 3D fire-diffuse-fire agent-based models. These data demonstrate that electrical wavefronts based on potassium ions are a mechanism by which signaling occurs in Gram-negative biofilms and as such may represent a conserved mechanism for communication across biofilms.
