The ROMK immunoglobulin-like domain with select residues mutated in Bartter syndrome are highlighted. Mutations tested in the recently published study: A198T (yellow), R212P (purple), H270Y (orange), Y314C (red). Other mutations of interest and discussed in the text: I211S (green), S276N (cyan), L297S (dark blue). Representations rendered with PyMol molecular graphics system version 1.8.