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Nord AL, Biquet-Bisquert A, Abkarian M, Pigaglio T, Seduk F, Magalon A, Pedaci F. Dynamic stiffening of the flagellar hook. Nat Commun 2022; 13:2925. [PMID: 35614041 PMCID: PMC9133114 DOI: 10.1038/s41467-022-30295-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 04/22/2022] [Indexed: 11/09/2022] Open
Abstract
For many bacteria, motility stems from one or more flagella, each rotated by the bacterial flagellar motor, a powerful rotary molecular machine. The hook, a soft polymer at the base of each flagellum, acts as a universal joint, coupling rotation between the rigid membrane-spanning rotor and rigid flagellum. In multi-flagellated species, where thrust arises from a hydrodynamically coordinated flagellar bundle, hook flexibility is crucial, as flagella rotate significantly off-axis. However, consequently, the thrust applies a significant bending moment. Therefore, the hook must simultaneously be compliant to enable bundle formation yet rigid to withstand large hydrodynamical forces. Here, via high-resolution measurements and analysis of hook fluctuations under dynamical conditions, we elucidate how it fulfills this double functionality: the hook shows a dynamic increase in bending stiffness under increasing torsional stress. Such strain-stiffening allows the system to be flexible when needed yet reduce deformation under high loads, enabling high speed motility. Bacterial motility relies on the mechanics of the “hook” the 60 nm biopolymer at the base of rotating flagella. Here, authors observe the hook stiffening as it is twisted by the rotation of the flagellum, a mechanical feat evolved for its function.
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Affiliation(s)
- Ashley L Nord
- Centre de Biologie Structurale, Univ. Montpellier, CNRS, INSERM, Montpellier, France
| | - Anaïs Biquet-Bisquert
- Centre de Biologie Structurale, Univ. Montpellier, CNRS, INSERM, Montpellier, France
| | - Manouk Abkarian
- Centre de Biologie Structurale, Univ. Montpellier, CNRS, INSERM, Montpellier, France
| | - Théo Pigaglio
- Aix Marseille Université, CNRS, Laboratoire de Chimie Bactérienne (UMR7283), IMM, IM2B, 13402, Marseille, France
| | - Farida Seduk
- Aix Marseille Université, CNRS, Laboratoire de Chimie Bactérienne (UMR7283), IMM, IM2B, 13402, Marseille, France
| | - Axel Magalon
- Aix Marseille Université, CNRS, Laboratoire de Chimie Bactérienne (UMR7283), IMM, IM2B, 13402, Marseille, France
| | - Francesco Pedaci
- Centre de Biologie Structurale, Univ. Montpellier, CNRS, INSERM, Montpellier, France.
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Sielaff H, Dienerowitz F, Dienerowitz M. Single-molecule FRET combined with electrokinetic trapping reveals real-time enzyme kinetics of individual F-ATP synthases. NANOSCALE 2022; 14:2327-2336. [PMID: 35084006 DOI: 10.1039/d1nr05754e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a key technique to observe conformational changes in molecular motors and to access the details of single-molecule static and dynamic disorder during catalytic processes. However, studying freely diffusing molecules in solution is limited to a few tens of milliseconds, while surface attachment often bears the risk to restrict their natural motion. In this paper we combine smFRET and electrokinetic trapping (ABEL trap) to non-invasively hold single FOF1-ATP synthases for up to 3 s within the detection volume, thereby extending the observation time by a factor of 10 as compared to Brownian diffusion without surface attachment. In addition, we are able to monitor complete reaction cycles and to selectively trap active molecules based on their smFRET signal, thus speeding up the data acquisition process. We demonstrate the capability of our method to study the dynamics of single molecules by recording the ATP-hydrolysis driven rotation of individual FOF1-ATP synthase molecules over numerous reaction cycles and extract their kinetic rates. We argue that our method is not limited to motor proteins. Instead, it can be applied to monitor conformational changes with millisecond time resolution for a wide range of enzymes, thereby making it a versatile tool for studying protein dynamics.
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Affiliation(s)
- Hendrik Sielaff
- Department of Chemistry, Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, 117557 Singapore, Singapore
| | - Frank Dienerowitz
- Ernst-Abbe-Hochschule Jena, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
| | - Maria Dienerowitz
- Single-Molecule Microscopy Group, Universitätsklinikum Jena, Nonnenplan 2-4, 07743 Jena, Germany.
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