Human WNK4, sortilin, and NCC are shown with predicted domains used in the experiment. (A) Myc-tagged WNK4 WT with predicted domains. KD, kinase domain; AI, autoinhibitory domain; Cc, coiled coil domain. (B) GFP-tagged sortilin WT and its truncated mutant sortilin TRU lacking its cytoplasmic tail. Pp, propeptide; LD, luminal domain; T, transmembrane region; Ct, cytoplasmic tail. (C) GST-tagged NCC WT and its amino terminus of NCC (1 through 135) and carboxyl terminus of NCC (605 through 1031). NT, amino terminus; T, transmembrane domain, CT, carboxyl terminus.