Functions as a beta-subunit for CLCNKA and CLCNKB chloride channels. In the kidney CLCNK/BSND heteromers mediate chloride reabsorption by facilitating its basolateral efflux. In the stria, CLCNK/BSND channels drive potassium secretion by recycling chloride for the basolateral SLC12A2 cotransporter. Interacts with CLCNK channels. Forms heteromers with CLCNKA in the thin ascending limb of Henle and with CLCNKB in the thick ascending limb and more distal segments (By similarity). A significant amount also observed intracellularly. Staining in membranes of the renal tubule and of potassium-secreting epithelia of the inner ear is basolateral (By similarity). Expressed primarily in kidney. Expressed in specific nephron segments and in the stria vascularis of the inner ear. Palmitoylation is necessary for activation of plasma membrane-inserted CLC-K/barttin channels. The disease is caused by variants affecting the gene represented in this entry.