Auxiliary protein of the large-conductance, voltage and calcium-activated potassium channel (BK alpha). Modulates gating properties by producing a marked shift in the BK channel's voltage dependence of activation in the hyperpolarizing direction, and in the absence of calcium. KCNU1 channel auxiliary protein. Modulates KCNU1 gating properties. {ECO:0000269|PubMed:22547800, ECO:0000269|PubMed:23129643}. This is the function of LRRC52 (leucine rich repeat containing 52, Ensembl gene identifier ENSG00000162763).