| Abstract: | We isolated and characterized a novelK-Cl cotransporter, KCC3, from human placenta. The deduced proteincontains 1,150 amino acids. KCC3 shares 75-76% identity at theamino acid level with human, pig, rat, and rabbit KCC1 and 67%identity with rat KCC2. KCC3 is 40 and 33% identical to twoCaenorhabditis elegans K-Cl cotransporters and ~20%identical to other members of the cation-chloride cotransporter family(CCC), two Na-K-Cl cotransporters (NKCC1, NKCC2), and the Na-Clcotransporter (NCC). Hydropathy analysis indicates a typical KCCtopology with 12 transmembrane domains, a large extracellular loopbetween transmembrane domains 5 and 6 (unique to KCCs), and largeNH2 and COOH termini. KCC3 is predominantly expressed inkidney, heart, and brain, and is also expressed in skeletal muscle,placenta, lung, liver, and pancreas. KCC3 was localized to chromosome15. KCC3 transiently expressed in human embryonic kidney (HEK)-293cells fulfilled three criteria for increased expression of K-Clcotransport: stimulation of cotransport by swelling, treatment withN-ethylmaleimide, or treatment with staurosporine. |
