The function of Ensembl gene identifier ENSG00000162399 (BSND, barttin CLCNK type accessory subunit beta) is as follows. Regulatory subunit of anion-selective CLCNKA:BSND and CLCNKB:BSND heteromeric channels involved in basolateral chloride conductance along the nephron to achieve urine concentration and maintain systemic acid-base homeostasis, and in the stria vascularis of the inner ear to establish the endocochlear potential necessary for normal hearing (PubMed:11734858, PubMed:12111250, PubMed:12574213, PubMed:16849430, PubMed:18776122, PubMed:19646679, PubMed:20538786, PubMed:26013830). Most likely acts as a chaperone that allosterically regulates proper sorting of CLCNKA:BSND and CLCNKB:BSND channels at the basolateral plasma membrane domain and functional switch to ion conducting state. Mediates constitutive opening of channel common gates (PubMed:11734858, PubMed:12111250, PubMed:12574213, PubMed:16849430, PubMed:18776122, PubMed:19646679, PubMed:20538786, PubMed:26013830). {ECO:0000269|PubMed:11734858, ECO:0000269|PubMed:12111250, ECO:0000269|PubMed:12574213, ECO:0000269|PubMed:16849430, ECO:0000269|PubMed:18776122, ECO:0000269|PubMed:19646679, ECO:0000269|PubMed:20538786, ECO:0000269|PubMed:26013830}.