TCB Publications - Abstract

Milana Fraiberg, Oshri Afanzar, C. Keith Cassidy, Alexandra Gabashvili, Klaus Schulten, Yishai Levin, and Michael Eisenbach. CheY's acetylation sites responsible for generating clockwise flagellar rotation in Escherichia coli. Molecular Microbiology, 95:231-244, 2015. (PMC: PMC4426874)

FRAI2015 Stimulation of Escherichia coli with acetate elevates the acetylation level of the chemotaxis response regulator CheY. This elevation, in an unknown mechanism, activates CheY to generate clockwise rotation. Here, using quantitative selective reaction monitoring mass spectrometry and high-resolution targeted mass spectrometry, we identified K91 and K109 as the major sites whose acetylation level in vivo increases in response to acetate. Employing single and multiple lysine replacements in CheY, we found that K91 and K109 are also the sites mainly responsible for acetate-dependent clockwise generation. Furthermore, we showed that clockwise rotation is repressed when residue K91 is non-modified, as evidenced by an increased ability of CheY to generate clockwise rotation when K91 was acetylated or replaced by specific amino acids. Using molecular dynamics simulations we show that K91 repression is manifested in the conformational dynamics of the $\beta$4$\alpha$4 loop, shifted towards an active state upon mutation. Removal of $\beta$4$\alpha$4 loop repression may represent a general activation mechanism in CheY, pertaining also to the canonical phosphorylation activation pathway as suggested by crystal structures of active and inactive CheY from Thermotoga maritima. By way of elimination we further suggest that K109 acetylation is actively involved in generating clockwise rotation.

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