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. Author manuscript; available in PMC: 2013 Jan 6.
Published in final edited form as: Cell. 2012 Jul 6;150(1):222–232. doi: 10.1016/j.cell.2012.05.033

Figure 6. Adaptive divergence of duplicated signaling pathways involves the elimination of cross-talk.

Figure 6

Ovals represent the set of response regulators recognized by a histidine kinase, as determined by its specificity residues (see also Figure 5). The NtrB-NtrC pathway is shown duplicating to produce the paralogous system NtrY-NtrX. As these pathways diverged, the specificity of NtrY overlapped that of PhoR, necessitating a change in PhoR specificity to yield the derived state with insulated pathways.