LRRC26 auxiliary protein allows BK channel activation at resting voltage without calcium RES Here the authors show that in non-excitable LNCaP prostate cancer cells, the large-conductance, voltage- and calcium-activated potassium (BK) channel can be activated at negative voltages without rises in intracellular Ca2+ concentration, by interacting with an auxiliary protein, the leucine-rich repeat containing protein 26. This auxiliary protein modulates BK channel gating by enhancing the allosteric coupling between voltage-sensor activation and the channel's closed–open transition.