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Signaling-Related Mobility Changes in Bacterial Chemotaxis Receptors Revealed by Solid-State NMR.
- Source :
-
Journal of Physical Chemistry B . Sep2017, Vol. 121 Issue 37, p8693-8705. 13p. - Publication Year :
- 2017
-
Abstract
- Bacteria employ remarkable membrane-bound nanoarrays to sense their environment and direct their swimming. Arrays consist of chemotaxis receptor trimers of dimers that are bridged at their membrane-distal tips by rings of two cytoplasmic proteins, a kinase CheA and a coupling protein CheW. It is not clear how ligand binding to the periplasmic domain of the receptor deactivates the CheA kinase bound to the cytoplasmic tip ~300 Å away, but the mechanism is thought to involve changes in dynamics within the cytoplasmic domain. To test these proposals, we applied solid-state NMR mobility-filtered experiments to functional complexes of the receptor cytoplasmic fragment (U-13C,15N-CF), CheA, and CheW. Assembly of these proteins into native-like, homogeneous arrays is mediated by either vesicle binding or molecular crowding agents, and paramagnetic relaxation enhancement is used to overcome sensitivity challenges in these large complexes. INEPT spectra reveal that a significant fraction of the receptor is dynamic on the nanosecond or shorter time scale, and these dynamics change with signaling state. The mobile regions are identified through a combination of biochemical and NMR approaches (protein truncations and unique chemical shifts). The INEPT spectra are consistent with an asymmetric mobility in the methylation region (N-helix mobility ≫ C-helix mobility) and reveal an increase in the mobility of the N-helix in the kinase-off state. This finding identifies functionally relevant dynamics in the receptor, and suggests that this N-helix segment plays a key role in propagating the signal. [ABSTRACT FROM AUTHOR]
- Subjects :
- *CHEMOTAXIS
*BACTERIA
*PARAMAGNETISM
*DIMERS
*NUCLEAR magnetic resonance
Subjects
Details
- Language :
- English
- ISSN :
- 15206106
- Volume :
- 121
- Issue :
- 37
- Database :
- Academic Search Index
- Journal :
- Journal of Physical Chemistry B
- Publication Type :
- Academic Journal
- Accession number :
- 126065948
- Full Text :
- https://doi.org/10.1021/acs.jpcb.7b06475