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. Author manuscript; available in PMC: 2019 Aug 27.
Published in final edited form as: Curr Top Membr. 2018 Aug 27;81:3–52. doi: 10.1016/bs.ctm.2018.08.001

Figure 9. Diagram showing the two-state model of K-Cl cotransport activation/inactivation.

Figure 9.

A, A protein phosphatase (PP1) mediates a de-phosphorylation (activation) reaction of specific threonine residues (T991 & T1048) with a rate constant of k12, whereas a kinase (SPAK) mediates the opposite phosphorylation (inhibition) reaction of these same threonine residues with a different rate constant (k21). B, Measurement of 86Rb uptake versus time in rabbit red blood cells illustrates a lag phase occurs in the stimulation of the flux from flux0 to flux1. Water is added at arrow to decrease the medium’s osmolarity. Figure adapted/redrawn from (Jennings & al-Rohil, 1990).