Probable regulatory subunit of the calcium activated potassium KCNMA1 (maxiK) channel that modulates the calcium sensitivity and gating kinetics of KCNMA1, thereby contributing to KCNMA1 channel diversity. Increases the apparent Ca(2+)/voltage sensitivity of the KCNMA1 channel (By similarity). Probably interacts with KCNMA1 tetramer. Belongs to the KCNMB (TC 8.A.14.1) family. KCNMB1 subfamily.