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. Author manuscript; available in PMC: 2010 Jul 1.
Published in final edited form as: Mol Microbiol. 2009 Jun 1;73(1):5–19. doi: 10.1111/j.1365-2958.2009.06742.x

Figure 1.

Figure 1

The two-state model of chemoreceptor signaling. Methyl-accepting chemotaxis proteins (MCPs) or chemoreceptors regulate the activity of the signal-transducing histidine kinase CheA, which is coupled to MCPs through CheW. The MCP receptors can be viewed as having two activity states, one that is inhibitory with respect to the kinase and one that is activating. Attractant binding promotes the inhibitory state (and ultimately counter clockwise (CCW) rotation of the flagellar motor), whereas cytoplasmic methylation favors the activating state (and ultimately clockwise (CW) flagellar rotation). Action by the CheR methyltransferase, is countered by the CheB methylesterase, which itself is regulated by CheA through phosphorylation. In this way, kinase activity is used to reset the receptor state equilibrium as the bacteria swim up a gradient of ligand. Courtesy of Sandy Parkinson.