Bacteria employ remarkable ~200 nm membrane-bound nanoarrays to sense their environment and direct their swimming. Arrays consist of receptor trimers of dimers (rainbow) that extend perpendicular to the membrane to a “baseplate” where they are linked by hexagons of alternating CheA (black) and CheW (gray) proteins (Fig. 1). Binding of attractant ligands to the receptors causes a 2 Å downward piston of an alpha helix in the periplasmic and transmembrane domains (not shown). How does the signal propagate an additional ~200Å through the cytoplasmic domain to control the kinase CheA? Because changes in receptor dynamics are proposed to propagate the signal, we have used INEPT to selectively detect a mobile region within native-like arrays of U-<sup>13</sup>C,<sup>15</sup>N receptor cytoplasmic fragment (CF), CheA, and CheW assembled on vesicles. Chemical shifts of distinctive residues suggest that the mobile region is near the N terminus where CF is bound via its His tag to the vesicle surface. Comparison of 40 kHz MAS INEPT spectra of functional signaling states suggests increased flexibility of this region in the kinase-off state. Implications of these findings for structural models and proposed mechanisms will be discussed.

Signaling-related mobility changes in functional chemotaxis receptor arrays by solid-state NMR

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.