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. Author manuscript; available in PMC: 2009 Oct 24.
Published in final edited form as: J Mol Biol. 2008 Aug 9;382(5):1290–1297. doi: 10.1016/j.jmb.2008.08.009

Figure 4. QS signal recognition as an example of kinetic proofreading.

Figure 4

(A) The canonical Hopfield-Ninio (HN) model of kinetic proofreading with one cycle.

(B) QS signaling as two-cycle kinetic proofreading.

In QS, the degradation of the R-protein provides a second cycle of proofreading. R is a receptor protein (HN model) or an R-protein (QS model). A is a signaling molecule. RA is the complex of R and A. In the HN model, RA* the activated form RA. The star (*) in the QS model represents unspecified substrates or degradation products.