Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

20-POS Board 5 CONCERTED DIFFERENTIAL CHANGES OF HELICAL DYNAMICS AND PACKING INDUCED BY LIGAND OCCUPANCY IN A BACTERIAL CHEMORECEPTOR Jesse B Gordon 1 ; Mikaila C Hoffman 1 ; Julianne M Troiano 1 ; Mingshan Li 2 ; Gerald L Hazelbauer 2 ; Gabriela S Schlau-Cohen 1 ; 1 Massachusetts Institute of Technology, Chemistry, Cambridge, MA, USA 2 University of Missouri, Biochemistry, Columbia, MO, USA Bacterial infections can be initiated by detection of and motion towards favorable chemical environments in a process known as chemotaxis. Transmembrane chemoreceptors initiate chemotaxis upon ligand binding and generate conformational signals that regulate a histidine kinase. Ligand-induced signaling through the periplasmic and transmembrane domains of the receptor involves a piston-like helical displacement, but the nature of this signaling through the four-helix coiled coil of the cytoplasmic domain had not yet been identified. We performed single-molecule Förster Resonance Energy Transfer measurements on Escherichia coli aspartate receptor homodimers inserted into Nanodiscs. Upon ligand binding, changes in conformation and dynamics of the four-helix cytoplasmic coiled-coil domain were observed, and these ligand- induced effects were asymmetric across helical pairs. We suggest this reflects a conformational change in which the differential alterations to the packing and dynamics of the helices are coupled. These coupled changes could represent a previously unappreciated mode of conformational signaling that may well occur in other coiled-coil signaling proteins.

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