The renal pH-sensitive epithelial potassium channel Kir1.1 (ROMK) plays an important role in K+ homeostasis and mutations which disrupt this pH-sensing mechanism cause Type II Bartter's Syndrome. The pH-sensor is thought to be a anomalously titrated lysine residue (K80) that interacts with two arginine residues (R41 & R311) as part of an 'RKR Triad'. Here we show that a Kir1.1 ortholog from Fugu rubripes lacks a pH-sensor lysine residue in TM1 yet is still highly pH-sensitive, demonstrating that K80 is not the pH-sensor. Homology modelling shows that instead of interacting with K80, R41 forms an intra-subunit salt-bridge with E318, whilst R311 interacts with E302 on the adjacent C-terminus. Mutation of these highly-conserved interactions markedly affects Kir channel gating and thus pH-sensitivity indirectly. Further, residues 80 and 177 form an interaction pair at the 'helix-bundle crossing' that controls the ability of pH-dependent conformational changes to induce pore closure. Although dispensable for pH-inhibition, K80 is indispensable for the tight coupling of pH-gating to the extracellular K+ concentration, explaining its conservation in most Kir1.1 orthologs. This study presents a new mechanistic and structural insight into the role the RKR residues and their inter/intra-subunit interactions play in Kir channel gating, pH-sensitivity and sensitivity to extracellular K+.