Gf. Lee et al., TRANSMEMBRANE SIGNALING CHARACTERIZED IN BACTERIAL CHEMORECEPTORS BY USING SULFHYDRYL CROSS-LINKING IN-VIVO, Proceedings of the National Academy of Sciences of the United Statesof America, 92(8), 1995, pp. 3391-3395
Transmembrane signaling by bacterial chemoreceptors is thought to invo
lve conformational changes within a stable homodimer. We investigated
the functional consequences of constraining movement between pairs of
helices in the four-helix structure of the transmembrane domain of che
moreceptor Trg. Using a family of cysteine-containing receptors, we id
entified oxidation treatments for intact cells that catalyzed essentia
lly complete sulfhydryl cross-linking at selected positions and yet le
ft flagellar and sensory functions largely unperturbed. Constraining m
ovement by cross-links between subunits had little effect on tactic re
sponse, but constraining movement between transmembrane segments of th
e monomer drastically reduced function. We deduce that transmembrane s
ignaling requires substantial movement between transmembrane helices o
f a monomer but not between interacting helices across the interface b
etween subunits.