FIGURE 5.
PKA phosphorylation of AQP2 enhances its water permeability. A, stopped-flow analysis. Proteoliposomes or liposomes without protein incorporation were abruptly imposed to an inwardly directed osmotic gradient, and the vesicle shrinkage was monitored by measuring the increase in scattered light. The dots are measured values, and the solid lines are their fitted curves. Red, phosphorylated WT-AQP2-liposome; dark blue, non-phosphorylated WT-AQP2-liposome; green, non-phosphorylated WT-AQP2-liposome treated with HgCl2; light blue, Trx-liposome; black, liposome without protein incorporation. B, summary of osmotic water permeability (Pf). Data represent means ± S.E. from 15–20 independent experiments. *, p < 0.001 versus Trx-liposome; **, p < 0.001 versus non-phosphorylated AQP2-liposome.