The invention provides isolated nucleic acid and amino acid sequences of Slo2 and Slo4, members of the Slo family of potassium channel proteins, also known as “maxi” or BK potassium channel proteins. Also provided herein are antibodies to Slo2 and Slo 4, methods of detecting Slo2 and Slo 4, methods of screening for potassium channel activators and inhibitors using biologically active Slo2 and Slo 4, and kits for screening for activators and inhibitors of voltage-gated potassium channels comprising Slo2 and Slo 4.